Coasts & Habitats
Part 1 of 2
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Contents
Articles
Coastal Forms
1
Coast
1
Longshore drift
9
Swash
15
Spit (landform)
16
Shoal
18
Beach
22
Shingle beach
28
Shore
29
Sediment
31
Machair
38
Coastal erosion
39
Wave-cut platform
42
Lagoon
44
Estuary
46
River delta
52
Ports & Harbours
58
Harbor
58
Port
62
Coastal Management
67
Integrated coastal zone management
67
Coastal management
72
Hard Engineering
87
Groyne
87
Seawall
90
Revetment
93
Riprap
95
Gabion
97
Breakwater (structure)
99
Soft Engineering
103
Beach nourishment
103
Sand dune stabilization
109
Biodiversity & Environments
112
Littoral zone
112
Intertidal zone
115
Intertidal ecology
118
Kelp forest
123
Rocky shore
132
References
Article Sources and Contributors
135
Image Sources, Licenses and Contributors
139
Article Licenses
License
143
1
Coastal Forms
Coast
The coastline is where the land meets the sea or ocean.[1] A precise
line that can be called a coastline cannot be determined due to the
dynamic nature of tides. The term "coastal zone" can be used instead,
which is a spatial zone where interaction of the sea and land processes
occurs.[2] Both the terms coast and coastal are often used to describe a
geographic location or region; for example, New Zealand's West Coast,
or the East and West Coasts of the United States.
A pelagic coast refers to a coast which fronts the open ocean, as
opposed to a more sheltered coast in a gulf or bay. A shore, on the
other hand, can refer to parts of the land which adjoin any large body
of water, including oceans (sea shore) and lakes (lake shore). Similarly,
the somewhat related term "bank" refers to the land alongside or
sloping down to a river (riverbank) or to a body of water smaller than a
lake. "Bank" is also used in some parts of the world to refer to an
artificial ridge of earth intended to retain the water of a river or pond.
In other places this may be called a levee.
While many scientific experts might agree on a common definition of
the term "coast", the delineation of the extents of a coast differ
according to jurisdiction, with many scientific and government
authorities in various countries differing for economic and social
policy reasons.
Atlantic Ocean: The East Coast of Brazil
(Genipabu, Rio Grande do Norte).
Pacific Ocean: The West Coast Region of New
Zealand
Indian Ocean: coasts of the Andaman Islands,
India in the Bay of Bengal
Coast
2
Formation of Coasts
The main agents responsible for
deposition and erosion along coastlines
are waves, tides and currents. The
formation of coasts is also heavily
influenced by their lithology. The
harder the material the less likely it is
to erode or suffer the effects of
erosion. Variants in the rock create
different-shaped coastlines.
Tides often determine the range over
which sediment is deposited or eroded.
Areas with high tidal ranges allow waves to reach farther up the shore, and areas with lower tidal ranges produce
deposition at a smaller elevation interval. The tidal range is influenced by the size and shape of the coastline. Tides
do not typically cause erosion by themselves; however, tidal bores can erode as the waves surge up river estuaries
from the ocean.[3]
Atlantic rocky coastline, showing a surf area. Porto Covo, west coast of Portugal
Waves erode coastline as they break on shore releasing their energy;
the larger the wave the more energy it releases and the more sediment
it moves. Coastlines with longer shores have more room for the waves
to disperse their energy, while coasts with cliffs and short shore faces
give little room for the wave energy to be dispersed. In these areas the
wave energy breaking against the cliffs is higher, and air and water are
compressed into cracks in the rock, forcing the rock apart, breaking it
down. Sediment deposited by waves comes from eroded cliff faces and
is moved along the coastline by the waves.
Coastline of Grand Anse Beach, St. George's,
Grenada, West Indies
Sediment deposited by rivers is the dominant influence on the amount
of sediment located on a coastline.[4] Today riverine deposition at the
coast is often blocked by dams and other human regulatory devices, which remove the sediment from the stream by
causing it to be deposited inland.
Like the ocean which shapes them, coasts are a dynamic environment with constant change. The Earth's natural
processes, particularly sea level rise, waves and various weather phenomena, have resulted in the erosion, accretion
and reshaping of coasts as well as flooding and creation of continental shelves and drowned river valleys (rias).
Environmental importance
The coast and its adjacent areas on and off shore is an important part of a local ecosystem as the mixture of fresh
water and salt water in estuaries provides many nutrients for marine life. Salt marshes and beaches also support a
diversity of plants, animals, and insects crucial to the food chain.
The high level of biodiversity creates a high level of biological activity, which has attracted human activity for
thousands of years.
Coast
3
Human impacts
Human uses of coasts
An increasing part the global population inhabits coastal regions.[5]
Many of the world's major cities have been built on or near good
harbors and have port facilities. Jurisdictions that are landlocked have
achieved port status by such measures such as building canals.
The coast is a crucial frontier and must be defended against military
invaders, smugglers and illegal migrants. Fixed Coastal defenses have
long been erected in many nations and coastal countries also require a
navy and some form of coast guard.
Coasts, especially those with beaches and warm water are an important
draw for tourists. In many island nations such as those of the
Mediterranean, South Pacific and Caribbean, tourism is central to the
economy. Coasts are popular destinations because of recreational
activities such as swimming, fishing, surfing, boating, and sunbathing.
Growth management can be a challenge for coastal local authorities
who often struggle to provide the infrastructure required by new
residents.
A settled coastline in Marblehead, Massachusetts.
Once a fishing port, the harbor is now dedicated
to tourism and pleasure boating. Observe that the
sand and rocks have been darkened by oil slick
up to the high-water line.
Threats to a coast
Coasts also face many environmental challenges relating to
human-induced impacts. The human influence on climate change is
thought to be a contributing factor of an accelerated trend in sea level
rise which threatens coastal habitat.
Houses close to the coast, like these in Tiburon,
California, may be especially desirable
properties.
Pollution can occur from a number of sources: garbage and industrial
debris, the transportation of petroleum in tankers, increasing the
probability of large oil spills, small oil spills created by large and small vessels, which flush bilge water into the
ocean.
Fishing has diminished due to habitat degradation, overfishing, trawling, bycatch and climate change. Since the
growth of global fishing enterprises after the 1950’s, intensive fishing has gone from a few concentrated areas to
encompass nearly all fisheries. The scraping of the ocean floor in bottom dragging is devastating to coral, sponges
and other long-lived species that do not recover quickly. This destruction alters the functioning of the ecosystem and
can permanently alter species composition and biodiversity. Bycatch, the capture of unintended species in the course
of fishing, is typically returned the ocean only to die from injuries or exposure. Bycatch represents approximately ¼
of all marine catch. In the case of shrimp capture, the bycatch is five times larger than the shrimp caught.
Coast
4
Conservation
Extraordinary population growth in the 20th century has placed stress on the planet’s ecosystems. For example, on
Saint Lucia, harvesting mangrove for timber and clearing for fishing drove the mangrove forests to low levels,
resulting in a loss of habitat and spawning ground for marine life that was unique to the area. These forests also
helped to stabilize the coastline. Conservation efforts since the 1980’s have partially restored the ecosystem.
Types of coast
According to one principle of classification, an emergent coastline is a coastline which has experienced a fall in sea
level, because of either a global sea level change, or local uplift. Emergent coastlines are identifiable by the coastal
landforms, which are above the high tide mark, such as raised beaches. Alternatively, a submergent coastline is a
coastline which has experienced a rise in sea level, due to a global sea level change, local subsidence, or isostatic
rebound. Submergent coastlines are identifiable by their submerged, or "drowned" landforms, such as rias (drowned
valleys) and fjords.
According to a second principle of classification, a concordant coastline is a coastline where bands of different rock
types run parallel to the shore. These rock types are usually of alternating resistance, so the coastline forms
distinctive landforms, such as coves. A discordant coastline is a type of coastline formed when rock types of
alternating resistance run perpendicular to the shore. Discordant coastlines feature distinctive landforms because the
rocks are eroded by ocean waves. The less resistant rocks erode faster, creating inlets or bays; the more resistant
rocks erode more slowly, remaining as headlands or outcroppings.
Coastal landforms
The following articles describe some coastal landforms:
Coastal landforms. The feature shown here as a
bay would, in certain (mainly southern) parts of
Britain, be called a cove. That between the
cuspate foreland and the tombolo is a British bay.
•
•
•
Bay •
Cape •
Cove •
Gulf
Headland
Peninsula
Coast
5
Cliff erosion
• Much of the sediment deposited along a coast is the result of erosion of a surrounding Cliff, or bluff. Sea Cliffs
retreat landward because of the constant undercutting of slopes by waves. If the slope/cliff being undercut is made
of unconsolidated sediment it will erode at a much faster rate then a cliff made of bedrock. (Easterbrook 1999).
• A Natural arch is formed when a sea stacks is eroded through by waves.
• Sea caves are made when certain rock beds are more susceptible to erosion than the surrounding rock beds
because of different areas of weakness. These areas are eroded at a faster pace creating a hole or crevasse that,
through time, by means of wave action and erosion, becomes a cave.
• A Stack is formed when a headland is eroded away by wave and wind action.
• A Stump is a shortened sea stack that has been eroded away or fallen because of instability.
• Wave-cut notches are caused by the undercutting of overhanging slopes which leads to increased stress on cliff
material and a greater probability that the slope material will fall. The fallen debris accumulates at the bottom of
the cliff and is eventually removed by waves.
• A wave-cut platform forms after erosion and retreat of a sea cliff has been occurring for a long time. Gently
sloping wave-cut platforms develop early on in the first stages of cliff retreat. Later the length of the platform
decreases because the waves lose their energy as they break further off shore (Easterbrook 1999).
Rivers on the coastline
• Delta
• Estuary
Coastal features formed by sediment
•
•
•
Beach
•
Beach cusps •
Boondocks •
Dune system •
Mudflat
•
Raised beach •
Ria
•
Shoal
•
Strand plain •
Spit
Surge channel
Tombolo
Coastal features formed by another feature
• Lagoon
• Salt marsh
Other features on the coast
•
•
Concordant coastline •
Discordant coastline •
Fjord •
Island
Island arc •
Machair
Coastal processes
The following articles describe the various geologic processes that affect a coastal zone:
•
•
•
•
•
•
Attrition
•
Currents
•
Denudation •
Deposition
Erosion
Flooding
Longshore drift •
Saltation
Sea level change
•
•
eustatic
isostatic
Sedimentation
•
•
•
•
sediment transport
solution
sub-aerial processes
suspension
•
•
Tides
Water waves
•
•
•
•
•
diffraction
refraction
wave breaking
wave shoaling
Weathering
Coast
6
Wildlife
See also Seashore wildlife
Animals
Animals living along the coast vary enormously, some live along
coasts to nest like puffins, sea turtles and rockhopper penguins. Sea
snails and various kinds of barnacles live on the coast and scavenge on
food deposited by the sea. Most coastal animals are used to humans in
developed areas, such as dolphins and seagulls who eat food thrown
for them by tourists. Since the coastal areas are all part of the littoral
zone, there is a profusion of marine life found just off-coast.
250px][Coast of Ventura, CA
There are many kinds of seabirds on the coast. Pelicans and cormorants join up with terns and oystercatchers to
forage for fish and shellfish on the coast.
Plants
Coastal areas are famous for their kelp beds. Kelp is a fast growing seaweed that grows up to a metre a day. Corals
and anemones are true animals, but live a similar lifestyle as plants do. Mangroves and salt marsh are important
coastal vegetation types in topical and temperate environments respectively.
Coastline statistics
The coastline problem
At some time in the years immediately preceding 1951, Lewis Fry Richardson in researching the possible effect of
border lengths on the probability of war noticed that the Portuguese reported their measured border with Spain to be
987 km, but the Spanish reported it to be 1214 km. This was the beginning of the coastline problem, which is how to
arrive at an estimate of a boundary that is infinite.[6]
The prevailing method of estimating a border (or coastline) was to lay off n equal straight-line segments of length ℓ
with dividers on a map or aerial photograph. Each end of the segment must be on the boundary. Investigating the
discrepancies in border estimation Richardson discovered what is now termed the Richardson Effect: the sum of the
segments is inversely proportional to the common length of the segments. In effect, the shorter the ruler, the longer
the measured border; thus, the Spanish and Portuguese geographers were using different-length rulers.
The result most astounding to Richardson is that, as ℓ approaches zero, the length of the coastline approaches
infinity. Richardson had believed, based on Euclidean geometry, that a coastline would approach a fixed length, as
do similar estimations of regular geometric figures. For example, the perimeter of a regular polygon inscribed in a
circle approaches the circumference with increasing numbers of sides (and decrease in the length of one side). In
Geometric measure theory such a smooth curve as the circle that can be approximated by small straight segments
with a definite limit is termed a rectifiable curve.
Coast
7
Describing a coastline
More than a decade after Richardson's work was finished, Benoît Mandelbrot invented a new branch of mathematics,
fractal geometry, to describe just such non-rectifiable complexes in nature as the infinite coastline.[7] His own
definition of the new figure serving as the basis for his study is:[8]
I coined fractal from the Latin adjective fractus. The corresponding Latin verb frangere means "to break:" to
create irregular fragments. It is therefore sensible ... that, in addition to "fragmented" ... fractus should also
mean "irregular."
A key property of the fractal is self-similarity; that is, at any scale the same general configuration appears. A
coastline is perceived as bays alternating with promontories. No matter how greatly any one small section of
coastline is magnified, a similar pattern of bays and promontories on bays and promontories appears, right down to
the grains of sand. At that scale the coastline appears as a momentarily shifting, potentially infinitely long thread
with a stochastic arrangement of bays and promontories formed from the small objects at hand. In such a real
environment (as opposed to smooth curves) Mandelbrot asserts[7] "coastline length turns out to be an elusive notion
that slips between the fingers of those who want to grasp it."
A coastline is definitely to be represented by a fractal. However, there are different kinds of fractals. A coastline is in
"a first category of fractals, namely curves whose fractal dimension is greater than 1." That last statement represents
an extension by Mandelbrot of Richardson's thought. Mandelbrot's statement of the Richardson Effect is:[9]
where L, coastline length, a function of the measurement unit, ε, is approximated by the expression. F is a constant
and D is a parameter that Richardson found depended on the coastline approximated by L. He gave no theoretical
explanation but Mandelbrot identified L with a non-integer form of the Hausdorff dimension, later the fractal
dimension. Rearranging the right side of the expression obtains:
where Fε-D must be the number of units ε required to obtain L. The fractal dimension is the number of the
dimensions of the figure being used to approximate the fractal: 0 for a dot, 1 for a line, 2 for a square. D in the
expression is between 1 and 2, for coastlines typically less than 1.5. The broken line measuring the coast does not
extend in one direction nor does it represent an area, but is intermediate. It can be interpreted as a thick line or band
of width 2ε. More broken coastlines have greater D and therefore L is longer for the same ε. Mandelbrot showed that
D is independent of ε.
Notes
[1] "Coast" (http:/ / www. bartleby. com/ 61/ 43/ C0434300. html). The American Heritage Dictionary of the English Language: Fourth Edition.
2000. . Retrieved 2008-12-11.
[2] Nelson, Stephen A. (2007). "Coastal Zones" (http:/ / www. tulane. edu/ ~sanelson/ geol204/ coastalzones. htm). . Retrieved 2008-12-11.
[3] Davidson (2002), p.421.
[4] Easterbrook (1999).
[5] Goudarzi, Sara (July 18, 2006). "Flocking to the Coast: World's Population Migrating into Danger" (http:/ / www. livescience. com/
environment/ 060718_map_settle. html). Live Science. . Retrieved 2008-12-14.
[6] Drazin, P.G. (1993). "Fractals". In Ashford, Oliver M.; Charnock, H.; Drazin, P. G. et al.. The Collected Papers of Lewis Fry Richardson:. 1,
Meteorology and numerical analysis. Cambridge University Press (CUP) Archive. pp. 45–46. ISBN 0521382971, ISBN 9780521382977..
[7] Mandelbrot (1983) page 28.
[8] Mandelbrot (1983), page 1.
[9] Mandelbrot (1983), pages 29–31.
Coast
8
See also
•
Ballantine Scale
•
Land reclamation
•
Coastal and Estuarine Research Federation
•
List of countries by length of coastline
•
Coastal biogeomorphology
•
List of U.S. states by coastline
•
Coastal erosion
•
Marine debris
•
Coastal management
•
National Oceanic and Atmospheric Administration Climate and
Societal Interactions Program
•
Coastline of the North Sea
•
Nautical chart
•
Coral reefs
•
Pole of inaccessibility
•
How Long Is the Coast of Britain? Statistical Self-Similarity and
Fractional Dimension
•
Seaside resort
References
• Burke, Lauretta A.; Kura, Yumiko; Kassem, Ken; Revenga, Carmen; Spalding, Mark; McAllister, Don (2001).
"Coastal Ecosystems" (http://pdf.wri.org/Page_coastal.pdf). In Hutter, Carolynne. Pilot Analysis of Global
Ecosystems. World Resources Institute. ISBN 1-56973-458-5.
• Davidson, Jon P.; Reed, Walter E.; Davis, Paul M. (2002). Exploring Earth: An Introduction to Physical Geology.
Upper Saddle River, NJ: Prentice-Hall Inc. ISBN 0130183725, ISBN 9780130183729.
• Easterbrook, Don J. (1999). Surface Processes and Landforms (2 ed.). Upper Saddle River, NJ: Prentice-Hall Inc.
ISBN 0138609586, ISBN 9780138609580.
• Haslett, Simon K. (2009). Coastal Systems (2nd Edition). introduction to environment. New York: Routledge.
ISBN 9780415440608.
• Mandelbrot, Benoit B.. "II.5 How long is the coast of Britain?". The Fractal Geometry of Nature. Macmillan.
pp. 25–33. ISBN 0716711869, ISBN 9780716711865.
External links
• "Wild Coast USA" (http://www.wildcoast-usa.com/). Sierra Club. Retrieved 2008-12-11.
• "Data Explorer" (http://nosdataexplorer.noaa.gov/nosdataexplorer/). NOAA's National Ocean Service.
Retrieved 2008-12-11.
Longshore drift
9
Longshore drift
Longshore drift consists of the transport of
sediments (generally sand but may also
consist of coarser sediments such as gravels)
along a coast at an angle to the shoreline,
which is dependent on prevailing wind
direction, swash and backwash [1] This
process occurs in the littoral zone, and in or
within close proximity to the surf zone. The
process is also known as longshore
transport, littoral drift and LSD[2] .
Figure 1. Diagram demonstrating longshore drift
Longshore drift is influenced by numerous
aspects of the coastal system, with processes that occur within the surf zone largely influencing the deposition and
erosion of sediments. Longshore currents can generate oblique breaking waves which result in longshore transport.[3]
Longshore drift can generally be defined in terms of the systems within the surf zone as seen in figure 1. This figure
shows that sediment transport along the shore and surf zone is influenced by the swash (occurs in the direction of
prevailing wind), which moves the pebble up the beach at the angle of wind direction and also backwash, which
moves the pebble back down the beach due to the influence of gravity.
Longshore drift affects numerous sediment sizes as it works in slightly different ways depending on the sediment
(e.g. the difference in long shore drift of sediments from a sandy beach to that of sediments from a shingle beach).
Sand is largely affected by the oscillatory force of breaking waves, the motion of sediment due to the impact of
breaking waves and bed shear from long shore current [4] . Whereas due to the fact that shingle beaches are much
steeper than sandy ones, plunging breakers are more likely to form, causing the majority of long shore transport to
occur in the swash zone, due to a lack of surf zone [5] .
Overview
Longshore drift formulas
There are numerous calculations that take into consideration the factors that produce longshore drift. These
formulations are:
1.
2.
3.
4.
5.
6.
Bijker formula (1967,1971)
The Engelund and Hansen formula (1967)
The Ackers and White formula (1973)
The Bailard and Inman formula(1981)
The Van Rijn formula (1984)
The Watanabe formula (1992)[6]
These formulas all provide a different view into the processes that generate longshore drift. The most common
factors taken into consideration in these formulas are:
• Suspended and bed load transport
• Waves e.g. breaking and non-breaking
• The shear exerted by waves or the flow associated with waves [7] .
Longshore drift
10
Features of shoreline change
Longshore drift plays a large role in the evolution of a shoreline, as if there is a slight change of sediment supply,
wind direction, or any other coastal influence longshore drift can change dramatically, impacting on the formation
and evolution of a beach system or profile. These changes do not occur due to one factor within the coastal system,
in fact there are numerous alterations that can occur within the coastal system that may affect the distribution and
impact of longshore drift. Some of these are:
1.
2.
3.
4.
Geological changes, e.g. erosion, backshore changes and emergence of headlands.
Change in hydrodynamic forces, e.g. change in wave diffraction in headland and offshore bank environments.
Change to hydrodynamic influences, e.g. the influence of new tidal inlets and deltas on drift.
Alterations of the sediment budget, e.g. switch of shorelines from drift to swash alignment, exhaustion of
sediment sources.
5. The intervention of humans, e.g. cliff protection, groynes, detached breakwaters [8] .
The sediment budget
The sediment budget takes into consideration sediment sources and sinks within a system
come from any source with examples of sources and sinks consisting of:
•
•
•
•
•
•
•
[9]
. This sediment can
Rivers
Lagoons
Eroding land sources
Artificial sources e.g. nourishment
Artificial sinks e.g. mining/extraction
Offshore transport
Deposition of sediment on shore
This sediment then enters the coastal system and is transported by longshore drift. A good example of the sediment
budget and longshore drift working together in the coastal system is inlet ebb-tidal shoals, which store sand that has
been transported by long shore transport [10] . As well as storing sand these systems may also transfer or by pass sand
into other beach systems, therefore inlet ebb-tidal shoal systems provide a good sources and sinks for the sediment
budget [11] .
Natural features
This section consists of features of long shore drift that occur on a coast where long shore drift occurs uninterrupted
by man-made structures.
Spits
Spits are formed when longshore drift travels past a point (e.g. river
mouth or re-entrant) where the dominant drift direction and shoreline
do not veer in the same direction [12] . As well as dominant drift
direction, spits are affected by the strength of wave driven current,
wave angle and the height of incoming waves [13] .
Figure 2. Provincetown Spit, at the northern end
of Cape Cod, was formed by longshore drift after
the end of the last Ice age.
Spits are landforms that have two important features, with the first
feature being the region at the up-drift end or proximal end (Hart et al.,
2008). The proximal end is constantly attached to land (unless
breached) and may form a slight “barrier” between the sea and an
Longshore drift
estuary or lagoon [14] . The second important spit feature is the down-drift end or distal end, which is detached from
land and in some cases, may take a complex hook-shape or curve, due to the influence of varying wave directions
[15]
.
As an example, the New Brighton spit in Canterbury, New Zealand, was created by longshore drift of sediment from
the Waimakariri River to the north [16] . This spit system is currently in equilibrium but undergoes phases of
deposition and erosion.
Barriers
Barrier systems are attached to the land at both the proximal and distal end and are generally widest at the down-drift
end [17] . These barrier systems may enclose an estuary or lagoon system, like that of Lake Ellesmere enclosed by the
Kaitorete Spit.
The Kaitorete Spit in Canterbury, New Zealand, is a barrier/spit system (which generally falls under the definition
barrier, as both ends of the landform are attached to land, but has been named a spit) that has existed below Banks
Peninsula for the last 8000 years [18] . This system has undergone numerous changes and fluctuations due to avulsion
of the Waimakariri River (which now flows to the north or Banks Peninsula), erosion and phases of open marine
conditions [19] . The system underwent further changes c.500 year BP, when longshore drift from the eastern end of
the “spit” system created the barrier, which has been retained due to ongoing longshore transport [20] .
Tidal inlets
The majority of tidal inlets on longshore drift shores accumulate sediment in flood and ebb shoals [21] . Ebb-deltas
may become stunted on highly exposed shores and in smaller spaces, whereas flood deltas are likely to increase in
size when space is available in a bay or lagoon system [22] . Tidal inlets can act as sinks and sources for large
amounts of material, which therefore impacts on adjacent parts of the coastline [23] .
The structuring of tidal inlets is also important for longshore drift as if an inlet is unstructured sediment may by pass
the inlet and form bars at the down-drift part of the coast [24] . Although this may also depend on the inlet size, delta
morphology, sediment rate and by passing mechanism [25] . Channel location variance and amount may also
influence the impact of long shore drift on a tidal inlet as well.
For example, the Arcachon lagoon is a tidal inlet system in South west France, which provides large sources and
sinks for longshore drift sediments. The impact of longshore drift sediments on this inlet system is highly influenced
by the variation in the number of lagoon entrances and the location of these entrances [26] . Any change in these
factors can cause severe down-drift erosion or down-drift accretion of large swash bars [27] .
11
Longshore drift
12
Human influences
This section consists of long shore drift features that occur unnaturally and in some cases (e.g. groynes, detached
breakwaters) have be constructed to enhance the effects of longshore drift on the coastline, but in other cases have a
negative impact on long shore drift (ports and harbours).
Groynes
Groynes are shore protection structures, placed at equal intervals along
the coastline in order to stop coastal erosion and generally cross the
intertidal zone [28] . Due to this, groyne structures are usually used on
coasts/shores with low net and high annual longshore drift in order to
retain the sediments lost in storm surges and further down the coast [29]
.
There are numerous variations to groyne designs with the three most
common designs consisting of:
Figure 3. Timber groyne from Swanage bay, UK
1. zig-zag groynes, which dissipate the destructive flows that form in
wave induced currents or in breaking waves.
2. T-head groynes, which reduce wave height through wave diffraction.
3. ‘Y’ head, a fish tail groyne system.[30] .
Artificial headlands
Artificial headlands are also shore protection structures, which are created in order to provide a certain amount of
protection to beaches or bays [31] . Although the creation of headlands involves accretion of sediments on the up-drift
side of the headland and moderate erosion of the down-drift end of the headland, this is undertaken in order to design
a stabilised system that allows material to accumulate in beaches further along the shore [32] .
Artificial headlands can occur due to natural accumulation or also through artificial nourishment.
Detached breakwaters
Figure 4.Picture showing the use of artificial
headlands and detached breakwaters in a coastal
system
Detached breakwaters are shore protection structures, created to build
up sandy material in order to accommodate drawdown in storm
conditions [33] . In order to accommodate drawdown in storm
conditions detached breakwaters have no connection to the shoreline,
which lets currents and sediment pass between the breakwater and the
shore [34] .This then forms a region of reduced wave energy, which
encourages the deposition of sand on the lee side of the structure [35] .
Detached breakwaters are generally used in the same way as groynes,
to build up the volume of material between the coast and the
breakwater structure in order to accommodate storm surges [36] .
Longshore drift
Ports and Harbours
The creation of ports and harbours throughout the world can seriously impact on the natural course of longshore
drift. Not only do ports and harbours pose a threat to longshore drift in the short term, they also pose a threat to
shoreline evolution [37] . The major influence the creation of a port or harbour can have on longshore drift is the
alteration of sedimentation patterns, which in turn may lead to accretion and/or erosion of a beach or coastal system
[38]
.
As an example, the creation of a port in Timaru, New Zealand in the late 1800s led to a significant change in the
longshore drift along the South Canterbury coastline [39] . Instead of longshore drift transporting sediment north up
the coast towards the Waimataitai lagoon, the creation of the port blocked the drift of these (coarse) sediments and
instead caused them to accret to the south of the port at South beach in Timaru [40] . The accretion of this sediment to
the south, therefore meant a lack of sediment being deposited on the coast near the Waimataitai lagoon (to the north
of the port), which led to the loss of the barrier enclosing the lagoon in the 1930s and then shortly after, the loss of
the lagoon itself [41] . As with the Waimataitai lagoon the Washdyke Lagoon, which currently lies to the north of the
Timaru port is undergoing erosion and may eventually breach causing loss of another lagoon environment.
Notes
[1] Brunn, 2005
[2] Brunn, 2005
[3] Reeve et al., 2004
[4] Reeve et al., 2004
[5] Reeve et al., 2004
[6] http:/ / www. tpub. com/ content/ ArmyCIR/ bayram_etal02/ bayram_etal020004. htm
[7] http:/ / www. tpub. com/ content/ ArmyCIR/ bayram_etal02/ bayram_etal020004. htm
[8] Reeve et al., 2004
[9] Brunn, 2005
[10] Brunn, 2005, Michel and Howa, 1997
[11] Brunn, 2005, Michel and Howa, 1997
[12] Hart et al., 2008
[13] IPetersen et al., 2008
[14] Hart et al., 2008, Petersen et al., 2008
[15] Hart et al., 2008, Petersen et al., 2008
[16] Hart et al., 2008
[17] Kirk and Lauder, 2000
[18] Soons et al., 1997
[19] Soons et al., 1997
[20] Soons et al., 1997
[21] Brunn, 2005
[22] Brunn, 2005
[23] Michel and Howa, 1997
[24] Michel and Howa, 1997
[25] Brunn, 2005
[26] Michel and Howa, 1997
[27] Michel and Howa, 1997
[28] Reeve et al., 2004
[29] Reeve et al., 2004
[30] Reeve et al., 2004
[31] Reeve et al., 2004
[32] Reeve et al., 2004
[33] Reeve et al., 2004
[34] Reeve et al., 2004
[35] Reeve et al., 2004
[36] Reeve et al., 2004
[37] Reeve et al., 2004
[38] Reeve et al., 2004
13
Longshore drift
[39] Hart et al., 2008
[40] Hart et al., 2008
[41] Hart et al., 2008
References
• Brunn, P.(ed) (2005). Port and coastal engineering developments in Science and technology. South Carolina:
P.Brunn.
• Hart, D.E; Marsden, I; Francis, M (2008). "Chapter 20: Coastal systems". In Winterbourne, M. Natural history of
Canterbury (3rd edn). Canterbury University Press 30p. pp. 653–684.
• Kirk, R.M; Lauder, G.A (2000). "Significant coastal lagoon systems in the South Island, New Zealand". Science
for conservation. DOC 46p. pp. 13–24.
• Michel, D; Howa, H.L (1997). "Morphodynamic behaviour of a tidal inlet system in a mixed-energy
environment". Physical chemical earth. 22. pp. 339–343.
• Peterson, D; Deigaard, R; Fredsoe, J (2008). "Modelling the morphology of sandy spits". Coastal engineering. 55.
pp. 671–684.
• Reeve, D; Chadwick, A; Fleming, C (2004). Coastal engineering-processes, theory and design practice. New
York: Spon Press.
• Soons, J.M; Schulmeister, J; Holt, S (1997). "The Holocene evolution of a well nourished gravelly barrier and
lagoon complex, Kaitorete "Spit", Canterbury, New Zealand". Marine Geology. 26. pp. 69–90.
• Soons, J.M; Schulmeister, J; Holt, S (1997). "The Holocene evolution of a well nourished gravelly barrier and
lagoon complex, Kaitorete "Spit", Canterbury, New Zealand". Marine Geology. 26. pp. 69–90.
External links
• Photos, animation and explanation for schools (http://www.geography-site.co.uk/pages/physical/coastal/
longshore.html), geography-site.co.uk
• Intranet.lissjunior.hants.sch.uk (http://intranet.lissjunior.hants.sch.uk/water/picsweb_ks2geography/flash/
g2reswa0015.swf) has a brief animation on longshore drift.
• USGS — Coastal Erosion on Cape Cod (http://woodshole.er.usgs.gov/staffpages/boldale/capecod/quest.
html), woodshole.er.usgs.gov
• Shore drift (http://www.ecy.wa.gov/programs/sea/pugetsound/bluffs/drift.html), ecy.wa.gov
• Longshore drift in South Carolina (http://www.cofc.edu/CGOInquiry/longshoredrift.htm), cofc.edu
14
Swash
15
Swash
Swash (uprush and backwash), in
geography, is the water that washes up
on shore after an incoming wave has
broken. This action will cause sand and
other light particles to be transported
up the beach. The direction of the
swash varies with the prevailing wind,
whereas the backwash is always
perpendicular to the coastline. This
may cause longshore drift.
The swash is strong on a constructive wave while the backwash is weak
Backwash current
Backwash current is a seaward
current that results from the receding
swash on the beach face, after a wave
breaks, joins the seaward movement of
the wave trough toward the next
incoming crest. The same orbital wave
movement that causes a ball to bob up
and down on the water causes the
trough to move back and up toward the
next wave crest. This is not what the
word "undertow" suggests, and this
term should not be used.
See also
• Rip current
• Swashbuckler
• Berm
The swash is weak on a destructive wave while the backwash is strong
Spit (landform)
Spit (landform)
A spit or sandspit is a deposition landform found off coasts. At
one end, spits connect to land, and extend into the sea.[1] A spit is
a type of bar or beach that develops where a re-entrant occurs,
such as at cove's headlands, by the process of longshore drift.
Longshore drift (also called littoral drift) occurs due to waves
meeting the beach at an oblique angle, and backwashing
perpendicular to the shore, moving sediment down the beach in a
zigzag pattern. Longshore drifting is complemented by longshore
currents, which transport sediment through the water alongside the
beach. These currents are set in motion by the same oblique angle
of entering waves that causes littoral drift and transport sediment
in a similar process.[2]
Hydrology and geology
Where the direction of the shore inland reenters, or changes
direction, such as at a headland, the longshore current spreads out
Diagram showing a spit
or dissipates. No longer able to carry the full load, much of the
sediment is dropped. This is also known as deposition. This
submerged bar of sediment allows littoral drift to continue to transport in the direction the waves are breaking,
forming an above-water spit. Without the complementary process of littoral drift, the bar would not build above the
surface of the waves becoming a spit and would instead be leveled off underwater.
Spits occur when longshore drift reaches a section of headland where the turn is greater than 30 degrees. They will
continue out into the sea until water pressure (such as from a river) becomes too much to allow the sand to deposit.
The spit may then be grown upon and become stable and often fertile. A spit may be considered a specialized form
of a shoal. As spits grow, the water behind them is sheltered from wind and waves, and a salt marsh is likely to
develop.
Wave refraction can occur at the end of a spit, carrying sediment around the end to form a hook or recurved spit.[1]
Wave refraction in multiple directions will cause a complex spit to form. Incoming waves that come in a direction
other than obliquely along the spit will halt the growth of the spit, shorten it or eventually destroy it entirely.[1]
The sediments that make up spits come from a variety of sources including rivers and eroding bluffs, and changes
there can have a large impact on spits and other coastal landforms. Activities such as logging and farming upstream
can increase the sediment load of rivers, which may hurt the intertidal environments around spits by smothering
delicate habitat. Roads or bulkheads built along bluffs can drastically reduce the volume of sediment eroded, so that
not enough material is being pushed along to maintain a given spit.
If the supply of sediment is interrupted the sand at the neck (landward side) of the spit may be moved towards the
head, eventually creating an island. If the supply isn't interrupted, and the spit isn't breached by the sea (or, if across
an estuary, the river) the spit may become a bar, with both ends joined to land, and form a lagoon behind the bar. If
an island lies offshore near where the coast changes direction, and the spit continues to grow until it connects the
island to the mainland, it is then called a tombolo.
The end of a spit attached to land is called the proximal end, and the end jutting out into water is called the distal
end.
16
Spit (landform)
17
Spits around the world
The longest spit in the World is the Arabat Spit in the Sea of Azov. It is
approximately 110 km long.
The largest spit in the United States is the Dungeness Spit on the
Olympic Peninsula in Washington (8.9 km).
Chamisso Island sand spit
Farewell Spit in New Zealand, at 32 km, is one of the longest in the
world. Farewell Spit, in the North West corner of the South Island is
believed to be caused by the strong prevailing winds and currents
bringing sand eroded from the Southern Alps of the South Island and
depositing these into Golden Bay.
Spits in the UK are caused by prevailing South-Westerly winds, which give the spits their direction. However, when
the direction of the wind changes for a short while the spit may change in direction for a short while forming a hook.
Many spits have hooked or curved ends. One spit in the UK can be found in Dorset. Chesil Beach is an 18-mile long
shingle that connects Weymouth to the Isle of Portland. Chesil Beach provides shelter to Weymouth and the village
of Chiswell from prevailing winds and waves.
Human settlement patterns
Since prehistory humans have chosen certain spit formations as sites for human habitation. In some cases such as
Chumash Native American prehistorical settlement, these sites have been chosen for proximity to marine resource
exploitation; for example, the Chumash settlement on the Morro Bay sandspit is one such location.[3]
See also
• List of spits (landforms)
• Shoal, a related landform
References
[1] Evans, O.F. 1942, The origin of spits, bars and related structures: Journal of Geology, v. 50, p. 846-863
[2] Duane, D.B. and James, W.R., 1980, Littoral transport in the surf zone elucidaed by an Eulerian sediment tracer experiment: Journal of
Sedimentary Petrology, v. 50, p. 929-942
[3] * C.Michael Hogan (2008) Morro Creek, The Megalithic Portal, ed. by A. Burnham (http:/ / www. megalithic. co. uk/ article.
php?sid=18502)
Spits
Shoal
18
Shoal
A shoal, sandbar (or just bar in context), or gravelbar
is a somewhat linear landform within or extending into
a body of water, typically composed of sand, silt or
small pebbles. A spit or sandspit is a type of shoal.
Shoals are characteristically long and narrow (linear)
and develop where a stream or ocean current promotes
deposition of granular material, resulting in localized
shallowing (shoaling) of the water. Shoals can appear
in the sea, in a lake, or in a river. Alternatively a bar
may separate a lake from the sea, as in the case of an
ayre. They are typically composed of sand, although
could be of any granular matter that the moving water
Sandbar between St. Agnes and Gugh on the Isles of Scilly off the
has access to and is capable of shifting around (for
coast of Cornwall
example, soil, silt, gravel, cobble, shingle, or even
boulders). The grain size of the material comprising a
bar is related to the size of the waves or the strength of the currents moving the material, but the availability of
material to be worked by waves and currents is also important.
The term bar can apply to landform features spanning a considerable range in size, from a length of a few meters in a
small stream to marine depositions stretching for hundreds of kilometres along a coastline, often called barrier
islands.
In a nautical sense, a bar is a shoal, similar to a reef: a shallow formation of (usually) sand that is a navigation or
grounding hazard, with a depth of water of six fathoms or less. It therefore applies to a silt accumulation that
shallows the entrance to the course of a river or creek.
Shoaling
When surface waves move towards shallow water, such as a beach,
they slow down, their wave height increases and the distance between
waves decreases. This behaviour is called shoaling, and the waves are
said to shoal. The waves may or may not build to the point where they
break, depending on how large they were to begin with, and how steep
the slope of the beach is. In particular, waves shoal as they pass over
submerged sandbanks or reefs. This can be treacherous for boats and
ships.
When a water wave enters shallow water it
"shoals", that is, it slows down and the wave
height increases.
Shoaling can also diffract waves, so the waves change direction. For
example, if waves pass over a sloping sandbank which is shallower at
one end than the other, then the shoaling effect will result in the waves slowing more at the shallow end. Thus the
wave fronts will refract, changing direction like light passing through a prism. Refraction also occurs as waves move
towards a beach if the waves come in at an angle to the beach, or if the beach slopes more gradually at one end than
the other.
Shoal
19
Sandbars and longshore bars
This bar forms (sometimes seaward of a trough) where
the waves are breaking, because the breaking waves set
up a shoreward current with a compensating
counter-current along the bottom. Also known as a
trough bar. Sand carried by the offshore moving bottom
current is deposited where the current reaches the wave
break.[1] Other longshore bars may lie further offshore,
representing the break point of even larger waves, or
the break point at low tide.
A sandbar off Suffolk County, Long Island, New York, August 2006.
Harbour and river bars
A harbour or river bar is a sedimentary deposit formed at a harbour
entrance or river mouth by the deposition of sediment or the action of
waves on the sea floor or adjacent beaches. A bar can form a dangerous
obstacle to shipping, preventing access to the river or harbour in
unfavourable weather conditions or at some states of the tide. Where
beaches are suitably mobile, or the river’s suspended and/or bed loads
are large enough, wave action can build up a bar to completely block a
river mouth, damming the river, preventing access for boats or
shipping, and causing flooding in the lower reaches of the river. This
situation will persist until the bar is eroded by the sea, or the dammed
river develops sufficient head to break through the bar.
The Doom Bar sand bank extends across the
River Camel estuary in Cornwall, UK
Shoals as geological units
In addition to longshore bars discussed above that are
relatively small features of a beach, the term shoal can
be applied to larger geological units that form off a
coastline as part of the process of coastal erosion.
These include spits and baymouth bars that form across
the front of embayments and rias. A tombolo is a bar
that forms an isthmus between an island or offshore
rock and a mainland shore.
The largest of the geological units of this kind is a
barrier island, such as occur along the East Coast of the
United States, along the Gulf coast, along the southern
coast of Belize and many other locations worldwide.
Shoals in the Mississippi River at Arkansas and Mississippi.
In places of re-entrance along a coastline (such as inlets, coves, rias, and bays), sediments carried by a longshore
current
will
fall
out
where
the
current
Shoal
20
dissipates, forming a spit. An area of water isolated behind a large
bar is called a lagoon. Over time, lagoons may silt up, becoming
salt marshes.
In some cases shoals may be precursors to beach expansion and
dunes formation, providing a source of windblown sediment to
augment such beach or dunes landforms.[2]
Specific geology
The barrier island can be separated into sections for easy study.
Lower shoreface
The shoreface is the part of the barrier where the ocean meets the
shore of the island. The barrier island body itself separates the
shoreface from the backshore and lagoon/tidal flat area.
Characteristics common to the lower shoreface are fine sands with
muds and possibly silt. Further out into the ocean the sediment
becomes finer. The effect from the waves at this point is weak
because of the depth. Bioturbation is common and many fossils
can be found here.
A tidal sandbar connecting the islands of Waya and
Wayasewa of the Yasawa Islands, Fiji
Middle shoreface
The middle shore face is located in the upper shoreface. The middle shoreface is strongly influenced by wave action
because of its depth. Closer to shore the grain size will be medium size sands with shell pieces common. Since wave
action is heavier, bioturbation is not likely.
Upper shoreface
The upper shoreface is constantly effected by wave action. This results in development of herringbone sedimentary
structures because of the constant differing flow of waves. Grain size is larger sands.
Foreshore
The foreshore is the area on land between high and low tide. Like the upper shoreface, it is constantly affected by
wave action. Cross bedding and lamination are present and coarser sands are present because of the high energy
present by the crashing of the waves. The sand is also very well sorted.
Backshore
The backshore is always above the highest water level point. The berm is also found here which marks the boundary
between the foreshore and backshore. Wind is the important factor here, not water. During strong storms high waves
and wind can deliver and erode sediment from the backshore.
Dunes
The dunes are located at the top of the backshore. The dunes are typical of a barrier island. The high sand dunes are
only affected by wind because of their height. Similarly, strong storms are the only thing that really affect the size of
the dunes. The dunes will display characteristics of typical eolian wind blown dunes. The difference here is that
dunes on a barrier island typically contain vegetation roots and marine bioturbation.
Shoal
21
Lagoon and tidal flats
The lagoon and tidal flat area is located behind the dune and backshore area. Here the water is still and this allows
for fine silts, sands, and muds to settle out. Lagoons can become host to an anaerobic environment. This will allow
high amounts of organic rich mud to form. Vegetation is also common.
Human habitation
Since prehistoric times humans have chosen some shoals as a site of habitation. In some early cases the locations
provided easy access to exploit marine resources.[3] In modern times these sites are sometimes chosen for the water
amenity or view, but many such locations are prone to storm damage.[4] [5]
See also
•
•
•
•
•
•
Bank (geography)
New York Barrier Islands
Ocean bank (topography)
Shingle beach
Tidal island
U.S. Coastal Barrier Resources Act of 1982
Notes
[1]
[2]
[3]
[4]
[5]
W. Bascom, 1980. Waves and Beaches. Anchor Press/Doubleday, Garden City, New York. 366 p
Mirko Ballarini, Optical Dating of Quartz from Young Deposits, IOS Press, 2006 146 pages, ISBN 158603616
C.Michael Hogan (2008) Morro Creek, ed. by Andy Burnham (http:/ / www. megalithic. co. uk/ article. php?sid=18502)
Dick Morris (2008) Fleeced
Jefferson Beale Browne (1912) Key West: The Old and the New, published by The Record company
Beach
22
Beach
A beach is a geological landform along the
shoreline of an ocean, sea or lake. It usually
consists of loose particles which are often
composed of rock, such as sand, gravel,
shingle, pebbles, waves or cobblestones.
The particles of which the beach is
composed can sometimes instead have
biological origins, such as shell fragments or
coralline algae fragments.
Wild beaches are beaches which do not have
lifeguards or trappings of modernity nearby,
such as resorts and hotels. They are
sometimes called undeclared, undeveloped,
undefined, or undiscovered beaches. Wild
beaches can be valued for their untouched
beauty and preserved nature. They are most
commonly found in less developed areas
such as Puerto Rico, Thailand or Indonesia.
A sand and shingle beach at Man O’War Cove, Dorset, England
Beaches often occur along coastal areas where wave or current action deposits and reworks sediments.
Overview
Although the seashore is most commonly associated with the word
"beach", beaches are found by the sea or ocean or lakes.
The term 'beach' may refer to:
• small systems in which the rock material moves onshore, offshore,
or alongshore by the forces of waves and currents; or
• geological units of considerable size.
The former are described in detail below; the larger geological units
are discussed elsewhere under bars.
There are several conspicuous parts to a beach, all of which relate to
the processes that form and shape it. The part mostly above water
(depending upon tide), and more or less actively influenced by the
waves at some point in the tide, is termed the beach berm. The berm is
the deposit of material comprising the active shoreline. The berm has a
crest (top) and a face — the latter being the slope leading down
towards the water from the crest. At the very bottom of the face, there
may be a trough, and further seaward one or more longshore bars:
slightly raised, underwater embankments formed where the waves first
start to break.
Grand Anse Beach, St. George's, Grenada, West
Indies
Four Mile Beach, Port Douglas, Queensland
Beach
23
The sand deposit may extend well inland from the berm crest, where
there may be evidence of one or more older crests (the storm beach)
resulting from very large storm waves and beyond the influence of the
normal waves. At some point the influence of the waves (even storm
waves) on the material comprising the beach stops, and if the particles
are small enough (sand size or smaller) , winds shape the feature.
Where wind is the force distributing the grains inland, the deposit
behind the beach becomes a dune.
These geomorphic features compose what is called the beach profile.
The beach profile changes seasonally due to the change in wave energy
experienced during summer and winter months. The beach profile is
higher during the summer due to the gentle wave action during this
season. The lower energy waves deposit sediment on the beach berm
and dune, adding to the beach profile. Conversely, the beach profile is
lower in the winter due to the increased wave energy associated with
storms. Higher energy waves erode sediment from the beach berm and
dune, and deposit it off shore, forming longshore bars. The removal of
sediment from the beach berm and dune decreases the beach profile.
The line between beach and dune is difficult to define in the field. Over
any significant period of time, sand is always being exchanged
between them. The drift line (the high point of material deposited by
waves) is one potential demarcation. This would be the point at which
significant wind movement of sand could occur, since the normal
waves do not wet the sand beyond this area. However, the drift line is
likely to move inland under assault by storm waves.
Waikiki in Hawaii, USA at sunset.
Bondi Beach, Sydney, Australia
Murudeshwar Beach, bhatkal, India
Beach formation
Beach
24
Beaches are the result of wave action by which waves or currents move
sand or other loose sediments of which the beach is made as these
particles are held in suspension. Alternatively, sand may be moved by
saltation (a bouncing movement of large particles). Beach materials
come from erosion of rocks offshore, as well as from headland erosion
and slumping producing deposits of scree. Some of the whitest sand in
the world, along Florida's Emerald Coast, comes from the erosion of
quartz in the Appalachian Mountains. A coral reef offshore is a
significant source of sand particles.
The shape of a beach depends on whether or not the waves are
constructive or destructive, and whether the material is sand or shingle.
Constructive waves move material up the beach while destructive
waves move the material down the beach. On sandy beaches, the
backwash of the waves removes material forming a gently sloping
beach. On shingle beaches the swash is dissipated because the large
particle size allows percolation, so the backwash is not very powerful,
and the beach remains steep. Cusps and horns form where incoming
waves divide, depositing sand as horns and scouring out sand to form
cusps. This forms the uneven face on some sand shorelines.
There are several beaches which are claimed to be the "World's
longest", including Praia do Cassino (254 km), Cox's Bazar,
Bangladesh (120 km), Marina Beach in Chennai, India, Fraser Island
beach, 90 Mile Beach in Australia and 90 Mile Beach in New Zealand
(88 km), Troia-Sines Beach (63 km) in Portugal and Long Beach,
Washington (which is about 40 km).
Classic Caribbean beach on the island of
Martinique - Les Salines
Malpe Beach, One of the most famous beaches in
India
Sand from Pismo Beach, California including
quartz, shell and rock fragments.
Beach
25
Beaches and recreation
Many beaches are very popular on warm sunny days. In the Victorian
era, many popular beach resorts were equipped with bathing machines
because even the all-covering beachwear of the period was considered
immodest. This social standard still prevails in many Muslim countries.
At the other end of the spectrum are topfree beaches and nude beaches
where clothing is optional or not allowed. In most countries social
norms are significantly different on a beach in hot weather, compared
to adjacent areas where similar behaviour might not be tolerated and
might possibly be persecuted because of this action.
Recreation on a California beach in the first
decade of the 20th century.
In more than thirty countries in Europe, South Africa, New Zealand,
Canada, Costa Rica, South America and the Caribbean, the best
recreational beaches are awarded Blue Flag status, based on such
criteria as water quality and safety provision. Subsequent loss of this
status can have a severe effect on tourism revenues.
Many beaches are very popular on warm sunny
Due to intense use by the expanding human population, beaches are
days such as Joss Bay beach in southern England.
often dumping grounds for waste and litter, necessitating the use of
beach cleaners and other cleanup projects. More significantly, many beaches are a discharge zone for untreated
sewage in most underdeveloped countries; even in developed countries beach closure is an occasional circumstance
due to sanitary sewer overflow. In these cases of marine discharge, waterborne disease from fecal pathogens and
contamination of certain marine species is a frequent outcome.
Beach tokens
Beach tokens, a form of season pass admission ticket, may be required for entrance, for people and even pets.[1] [2]
They are made of metal etc. durable material, to enable them to withstand swimming, so the bearer can just carry
them around his neck or on his swimsuit. Goals may be:
• restricting to only community members
• user fees for lifeguards, clean up
Artificial beaches
Some beaches are artificial; they are either permanent or temporary
(For examples see Monaco, Paris, Copenhagen, Rotterdam, Toronto,
Hong Kong and Singapore).
The soothing qualities of a beach and the pleasant environment offered
to the beachgoer are replicated in artificial beaches, such as "beach
style" pools with zero-depth entry and wave pools that recreate the
natural waves pounding upon a beach. In a zero-depth entry pool, the
bottom surface slopes gradually from above water down to depth.
Another approach involves so-called urban beaches, a form of public
park becoming common in large cities. Urban beaches attempt to
mimic natural beaches with fountains that imitate surf and mask city
noises, and in some cases can be used as a play park.
A combination of public carelessness and official
negligence has turned this beach in Dar es Salaam
into an open rubbish dump, posing a risk to
public health.
Beach
26
Beach nourishment involves pumping sand onto beaches to improve their health. Beach nourishment is common for
major beach cities around the world; however the beaches that have been nourished can still appear quite natural and
often many visitors are unaware of the works undertaken to support the health of the beach. Such beaches are often
not recognized (by consumers) as artificial.
A concept of IENCE has been devised to describe investment into the
capacity of natural environments. IENCE is Investment to Enhance the
Natural Capacity of the Environment and includes things like beach
nourishment of natural beaches to enhance recreational enjoyment and
snow machines that extend ski seasons for areas with an existing snow
economy developed upon a natural snowy mountain. As the name
implies IENCE is not quite mainstream natural science as its goal is to
artificially invest into an environment's capacity to support
Transparency of water on the beach island of
anthropogenic economic activity. An artificial reef designed to enhance
Hvar — Croatia.
wave quality for surfing is another example of IENCE. The Surfrider
Foundation has debated the merits of artificial reefs with members torn
between their desire to support natural coastal environments and opportunities to enhance the quality of surfing
waves. Similar debates surround Beach nourishment and Snow cannon in sensitive environments.
Beaches as habitat
A beach is an unstable environment which exposes plants and animals
to changeable and potentially harsh conditions. Some small animals
burrow into the sand and feed on material deposited by the waves.
Crabs, insects and shorebirds feed on these beach dwellers. The
endangered Piping Plover and some tern species rely on beaches for
nesting. Sea turtles also lay their eggs on ocean beaches. Seagrasses
and other beach plants grow on undisturbed areas of the beach and
dunes.
Ocean beaches are habitats with organisms adapted to salt spray, tidal
overwash, and shifting sands. Some of these organisms are found only
on beaches. Examples of these beach organisms in the southeast US
include plants like sea oats, sea rocket, beach elder, beach morning
glory aka Ipomoea pes-caprae, and beach peanut, and animals such as
mole crabs aka Hippoidea, coquina clams aka Donax, ghost crabs, and
white beach tiger beetles.[3]
See also
•
•
•
•
•
•
•
•
•
Backyard cricket
Beach cleaner
Beach evolution
Beach volleyball
Coast
Dune buggy
List of beaches
Pier
Sand art and play
A view of Ventura, California coastline.
Voidokilia beach, at southern-west Greece
Beach
•
•
•
•
27
Shore
Strand plain
Surfing
Urban beach
Jasybay lake beach, Kazakhstan
References
[1] "?" (http:/ / web. archive. org/ web/ 20080502161310/ http:/ / www. cityofevanston. org/ departments/ parks/ beach_season. shtml). City of
Evanston. Archived from the original (http:/ / www. cityofevanston. org/ departments/ parks/ beach_season. shtml) on May 2, 2008. .
Retrieved 13 September 2010.
[2] "?" (http:/ / web. archive. org/ web/ 20080804073912/ http:/ / www. cityofevanston. org/ departments/ parks/ beach_dog. shtml). City of
Evanston. Archived from the original (http:/ / www. cityofevanston. org/ departments/ parks/ beach_dog. shtml) on August 4, 2008. .
Retrieved 13 September 2010.
[3] Blair and Dawn Witherington (2007), Florida's Living Beaches, A Guide for the Curious Beachcomber, (Pineapple Press)
Further reading
• Bascom, W. 1980. Waves and Beaches. Anchor Press/Doubleday, Garden City, New York. 366 p.
External links
•
•
•
•
UNESCO beach erosion and formation (http://www.unesco.org/csi/pub/source/ero9.htm)
Beach habitats (http://www.nearctica.com/ecology/habitats/beaches.htm)
Sea Foam: What Is It? -- Beaufort County Library (http://www.bcgov.net/bftlib/seafoam.htm)
Seasonal beach profile (http://ux.brookdalecc.edu/staff/sandyhook/tripdata/beaches/profile.html)
Shingle beach
28
Shingle beach
A shingle beach is a beach which is armoured with pebbles or smallto medium-sized cobbles. Typically, the stone composition may grade
from characteristic sizes ranging from two to 200 mm diameter.
Pebbles on a shingle beach in Somerset, England
While this beach landform is most commonly associated with
Western Europe, examples are found in Bahrain, the United States
and in a number of other world regions, such as the east coast of
New Zealand's South Island, where they are associated with the
shingle fans of braided rivers.
The ecosystems formed by this unique association of rock and
sand allow colonization by a variety of rare and endangered
species.[1]
Formation
Shingle beach at Torrisdale Bay, Argyll And Bute,
Scotland
Shingle beaches are typically steep, because the waves easily flow
through the coarse, porous surface of the beach, decreasing the effect of backwash erosion and increasing the
formation of sediment into a steeply sloping beach [2] .
Notable shingle beaches
•
•
•
•
•
•
•
•
•
•
Alby, Öland, Sweden
Birdling's Flat, Canterbury, New Zealand
Brighton, England
Chesil Beach, England
Dungeness, England
Hawar Islands, Bahrain
Herne Bay, Kent, England
Omaha Beach, Normandy, France
Short Beach, Oregon, USA
The Stade, Hastings, England
Shingle beach
29
See also
• Storm beach
• Machair
References
[1] UK's rare shingle beaches at risk, Alex Kirby, BBC News Online, June 3, 2003 (http:/ / news. bbc. co. uk/ 1/ hi/ sci/ tech/ 2956600. stm)
[2] Easterbrook, Don J. Surface Processes and Landforms. 1999 Prentice-Hall Inc. Upper Saddle River, NJ
Shore
A shore or shoreline is the fringe of land at the edge of a large body of
water, such as an ocean, sea, or lake. In Physical Oceanography a shore is
the wider fringe that is geologically modified by the action of the body of
water past and present, while the beach is at the edge of the shore,
representing the intertidal zone where there is one.[1] In contrast to a coast,
a shore can border any body of water, while the coast must border an
ocean; that is, a coast is a type of shore. Shore is often substituted for coast
where an oceanic shore is meant.
Beachfront of Tel Aviv, Israel
Shores are influenced by the topography of the surrounding landscape, as
well as by water induced erosion, such as waves. The geological
composition of rock and soil dictates the type of shore which is created.
Developed shoreline of San Pedro, Belize.
Shore of Dürnstein
Shore
30
Shore of Grand Anse Beach, St. George's,
Grenada, West Indies
See also
•
•
•
•
•
•
•
Ballantine Scale
Beach
Beach evolution
Coast
Littoral zone
Marine Sciences Research Center
Strand plain
References
[1] Pickard, George L.; William J. Emery (1990). Descriptive Physical Oceanography (5, illustrated ed.). Elsevier. pp. 7–8. ISBN 075062759X,
0750627597.
External links
• "shore" (http://www.bartleby.com/61/7/S0360700.html). The American Heritage Dictionary of the English
Language (4 ed.). 2000.
• "shore" (http://www.merriam-webster.com/dictionary/shore). Merriam-Webster Online. 2009.
Sediment
31
Sediment
Sediment is naturally-occurring material that is broken down by
processes of weathering and erosion, and is subsequently transported
by the action of fluids such as wind, water, or ice, and/or by the force
of gravity acting on the particle itself.
Sediments are most often transported by water (fluvial processes)
transported by wind (aeolian processes) and glaciers. Beach sands and
river channel deposits are examples of fluvial transport and deposition,
though sediment also often settles out of slow-moving or standing
water in lakes and oceans. Desert sand dunes and loess are examples of
aeolian transport and deposition. Glacial moraine deposits and till are
ice transported sediments.
Classification
Sediment in the thalweg of Campbell creek in
Alaska.
Sediment can be classified based on its grain size and/or its
composition.
River Rhône flowing into Lake Geneva.
Sediment
32
Sediment billowing out from Italy's shore into the
Adriatic.
Grain size
Sediment size is measured on a log base 2 scale, called the "Phi" scale,
which classifies particles by size from "colloid" to "boulder".
Sediment in the Gulf of Mexico.
Sediment
33
Sediment off the Yucatan Peninsula.
φ scale
Size range
(metric)
Size range
(inches)
Aggregate class
(Wentworth)
Other names
< -8
> 256 mm
> 10.1 in
Boulder
-6 to -8
64–256 mm
2.5–10.1 in
Cobble
-5 to -6
32–64 mm
1.26–2.5 in
Very coarse gravel Pebble
-4 to -5
16–32 mm
0.63–1.26 in
Coarse gravel
Pebble
-3 to -4
8–16 mm
0.31–0.63 in
Medium gravel
Pebble
-2 to -3
4–8 mm
0.157–0.31 in
Fine gravel
Pebble
-1 to -2
2–4 mm
0.079–0.157 in
Very fine gravel
Granule
0 to -1
1–2 mm
0.039–0.079 in
Very coarse sand
1 to 0
0.5–1 mm
0.020–0.039 in
Coarse sand
2 to 1
0.25–0.5 mm 0.010–0.020 in
Medium sand
3 to 2
125–250 µm
Fine sand
4 to 3
62.5–125 µm 0.0025–0.0049 in
8 to 4
3.9–62.5 µm
0.00015–0.0025 in Silt
Mud
>8
< 3.9 µm
< 0.00015 in
Clay
Mud
>10
< 1 µm
< 0.000039 in
Colloid
Mud
0.0049–0.010 in
Very fine sand
Composition
Composition of sediment can be measured in terms of:
• parent rock lithology
• mineral composition
• chemical make-up.
This leads to an ambiguity in which clay can be used as both a size-range and a composition (see clay minerals).
Sediment
34
Sediment transport
Sediment is transported based on the strength of the flow that carries it
and its own size, volume, density, and shape. Stronger flows will
increase the lift and drag on the particle, causing it to rise, while larger
or denser particles will be more likely to fall through the flow.
Fluvial processes: rivers, streams, and overland flow
Particle motion
Rivers and streams carry sediment in their flows. This sediment can be
in a variety of locations within the flow, depending on the balance
between the upwards velocity on the particle (drag and lift forces), and
the settling velocity of the particle. These relationships are given in the
following table for the Rouse number, which is a ratio of sediment fall
velocity to upwards velocity.
Sediment builds up on human-made breakwaters
because they reduce the speed of water flow, so
the stream cannot carry as much sediment load.
Glacial transport of boulders. These boulders will
be deposited as the glacier retreats.
where
•
•
•
is the fall velocity
is the von Kármán constant
is the shear velocity
Mode of Transport
Rouse Number
Bed load
>2.5
Suspended load: 50% Suspended
>1.2, <2.5
Suspended load: 100% Suspended >0.8, <1.2
Wash load
<0.8
If the upwards velocity approximately equal to the settling velocity, sediment will be transported downstream
entirely as suspended load. If the upwards velocity is much less than the settling velocity, but still high enough for
the sediment to move (see Initiation of motion), it will move along the bed as bed load by rolling, sliding, and
saltating (jumping up into the flow, being transported a short distance then settling again). If the upwards velocity is
higher than the settling velocity, the sediment will be transported high in the flow as wash load.
As there are generally a range of different particle sizes in the flow, it is common for material of different sizes to
move through all areas of the flow for given stream conditions.
Sediment
35
Fluvial bedforms
Sediment motion can create self-organized structures such as ripples,
dunes, antidunes on the river or stream bed. These bedforms are often
preserved in sedimentary rocks and can be used to estimate the
direction and magnitude of the flow that deposited the sediment.
Surface runoff
Overland flow can erode soil particles and transport them downslope.
The erosion associated with overland flow may occur through different
methods depending on meteorological and flow conditions.
Wave ripples in stone
• If the initial impact of rain droplets dislodges soil, the phenomenon
is called rainsplash erosion.
• If overland flow is directly responsible for sediment entrainment but does not form gullies, it is called "sheet
erosion".
• If the flow and the substrate permit channelization, gullies may form; this is termed "gully erosion".
Key fluvial depositional environments
The major fluvial (river and stream) environments for deposition of sediments include:
1.
2.
3.
4.
5.
6.
7.
Deltas (arguably an intermediate environment between fluvial and marine)
Point bars
Alluvial fans
Braided rivers
Oxbow lakes
Levees
Waterfalls
Aeolian processes: wind
Wind results in the transportation of fine sediment and the formation of sand dune fields and soils from airborne
dust.
Glacial processes
Glaciers carry a wide range of sediment sizes, and deposit it in
moraines.
Mass balance
The overall balance between sediment in transport and sediment being
deposited on the bed is given by the Exner equation. This expression
states that the rate of increase in bed elevation due to deposition is
proportional to the amount of sediment that falls out of the flow. This
equation is important in that changes in the power of the flow changes
Glacial sediments from Montana
the ability of the flow to carry sediment, and this is reflected in patterns
of erosion and deposition observed throughout a stream. This can be localized, and simply due to small obstacles:
examples are scour holes behind boulders, where flow accelerates, and deposition on the inside of meander bends.
Erosion and deposition can also be regional: erosion can occur due to dam removal and base level fall. Deposition
can occur due to dam emplacement that causes the river to pool, and deposit its entire load or due to base level rise.
Sediment
36
Shores and shallow seas
Seas, oceans, and lakes accumulate sediment over time. The sediment could consist of terrigenous material, which
originates on land, but may be deposited in either terrestrial, marine, or lacustrine (lake) environments; or of
sediments (often biological) originating in the body of water. Terrigenous material is often supplied by nearby rivers
and streams or reworked marine sediment (e.g. sand). In the mid-ocean, living organisms are primarily responsible
for the sediment accumulation, their shells sinking to the ocean floor upon death.
Deposited sediments are the source of sedimentary rocks, which can contain fossils of the inhabitants of the body of
water that were, upon death, covered by accumulating sediment. Lake bed sediments that have not solidified into
rock can be used to determine past climatic conditions.
Key marine depositional environments
The major areas for deposition of sediments in the marine environment
include:
1. Littoral sands (e.g. beach sands, runoff river sands, coastal bars and
spits, largely clastic with little faunal content)
2. The continental shelf (silty clays, increasing marine faunal content).
3. The shelf margin (low terrigenous supply, mostly calcareous faunal
skeletons)
4. The shelf slope (much more fine-grained silts and clays)
5. Beds of estuaries with the resultant deposits called "bay mud".
One other depositional environment which is a mixture of fluvial and
marine is the turbidite system, which is a major source of sediment to
the deep sedimentary and abyssal basins as well as the deep oceanic trenches.
Holocene eolianite and a carbonate beach on
Long Island, Bahamas.
Any depression in a marine environment where sediments accumulate over time is known as a sediment trap.
Environmental issues
Erosion and agricultural sediment delivery to rivers
One cause of high sediment loads from slash and burn and shifting cultivation of tropical forests. When the ground
surface is stripped of vegetation and then seared of all living organisms, the upper soils are vulnerable to both wind
and water erosion. In a number of regions of the earth, entire sectors of a country have become erodible. For
example, on the Madagascar high central plateau, which constitutes approximately ten percent of that country's land
area, most of the land area is devegetated, and gullies have eroded into the underlying soil in furrows typically in
excess of 50 meters deep and one kilometer wide. This siltation results in discoloration of rivers to a dark red brown
color and leads to fish kills.
Erosion is also an issue in areas of modern farming, where the removal of native vegetation for the cultivation and
harvesting of a single type of crop has left the soil unsupported. Many of these regions are near rivers and drainages.
Loss of soil due to erosion removes useful farmland, adds to sediment loads, and can help transport anthropogenic
fertilizers into the river system, which leads to eutrophication.
Sediment
Dregs
Sediment in wine, beer, Turkish coffee or other beverages is known as dregs.
See also
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Bar (river morphology)
Beach cusps
Biorhexistasy
Bioswale
Decantation
Erosion
Exner equation
Particle size (grain size)
Regolith
Sand
Sediment precipitation
Sediment trap
Sedimentary depositional environment
Settling
Surface runoff
References
• Prothero, Donald R.; Schwab, Fred (1996), Sedimentary Geology: An Introduction to Sedimentary Rocks and
Stratigraphy, W. H. Freeman, ISBN 0716727269
• Siever, Raymond (1988), Sand, New York: Scientific American Library, ISBN 071675021X
• Nichols, Gary (1999), Sedimentology & Stratigraphy, Malden, MA: Wiley-Blackwell, ISBN 0632035781
• Cambridge, MA, H. G. (1978), Sedimentary Environments: Processes, Facies and Stratigraphy, Blackwell
Science, ISBN 0632036273
37
Machair
38
Machair
This article is about a geographic landform. For the TV series, see Machair (TV series)
The Gaelic word machair or machar refers to a fertile low-lying
grassy plain found on some of the north-west coastlines of Ireland and
Scotland, in particular the Outer Hebrides. Two distinct types exist:
• A type of sand-dune pasture, subject to agricultural cultivation,
which prevails in wet and windy conditions;
• The land between a beach and the area where sand encroaches on
peat bogs further inland.
The machair on Berneray, Outer Hebrides
Geology
In both cases, a machair is a former beach, left higher in elevation than
the current adjacent beach following a drop in sea level or isostasy.
Machairs largely owe their fertility to the fact their sand has a high
seashell content- sometimes as high as 90%. This sand is blown inland,
acts to neutralize the acidity of the peatbogs and results in the fertility
of the grassland.
The machair on Berneray
Ecology
Machairs have received considerable ecological and conservational attention, chiefly because of their unique
[1]
ecosystems. They can house rare carpet flowers, such as Irish Lady's Tresses, orchids and Yellow Rattle, along
with a diverse array of bird species including the corn crake, twite, dunlin, redshank and ringed plover, as well as
rare insects such as the northern colletes bee. Some machairs are threatened by erosion caused by rising sea levels as
well as by recreational use of vicinity beaches.
References
• Angus, S. (1997). The Outer Hebrides: the Shaping of the Islands". The White Horse Press. ISBN 1-874267-33-2
Endnotes
[1] Machair Profile (http:/ / www. wildlifehebrides. com/ environment/ machair/ )
External links
• Wildlife Hebrides - wildlife in the Outer Hebrides of Scotland. (http://www.wildlifehebrides.com/
environment/machair/)
• Living Landscape Series - Grasslands - Creating Grasslands (http://www.snh.org.uk/publications/on-line/
livinglandscapes/machair/whatis.asp)
Machair
39
• Action plan for Machair (http://www.ukbap.org.uk/UKPlans.aspx?ID=30)
Coastal erosion
Coastal erosion is the wearing away of land or the removal of
beach or dune sediments by wave action, tidal currents, wave
currents, or drainage (see also beach evolution). Waves, generated
by storms, wind, or fast moving motor craft, cause coastal erosion,
which may take the form of long-term losses of sediment and
rocks, or merely the temporary redistribution of coastal sediments;
erosion in one location may result in accretion nearby. The study
of erosion and sediment redistribution is called 'coastal
morphodynamics'. It may be caused by hydraulic action, abrasion,
and corrosion.
On non-rocky coasts, coastal erosion results in dramatic rock
formations in areas where the coastline contains rock layers or
fracture zones with varying resistance to erosion. Softer areas
become eroded much faster than harder ones, which typically
result in landforms such as tunnels, bridges, columns, and pillars.
Dunwich, the capital of the English medieval wool trade,
disappeared over the period of a few centuries due to redistribution
of sediment by waves. Human interference can also increase
coastal erosion: Hallsands in Devon, England, was a coastal
village that washed away overnight, an event possibly exacerbated
by dredging of shingle in the bay in front of it.
Many stretches of the East Anglia, England coastline
are prone to heavy levels of erosion, such as this
collapsed section of cliffs at Hunstanton, Norfolk.
The California coast, which has soft cliffs of sedimentary rock and is heavily populated, regularly has incidents of
housing damage as cliffs erode. Damage in Pacifica is shown at left. Devil's Slide, Santa Barbara and Malibu are
regularly affected.
The Holderness coastline on the east coast of England, just north of the Humber Estuary, is the fastest eroding
coastline in Europe due to its soft clay cliffs and powerful waves. Groynes and other artificial measures to keep it
under control has only accelerated the process further down the coast, because longshore drift starves the beaches of
sand, leaving them more exposed.
Wave action
Hydraulic action
Hydraulic action occurs when waves striking a cliff face compress air in cracks on the cliff face. This exerts
pressure on the surrounding rock, and can progressively splinter and remove pieces. Over time, the cracks can grow,
sometimes forming a cave. The splinters fall to the sea bed where they are subjected to further wave action.
Attrition
Attrition occurs when waves causes loose pieces of rock debris (scree) to collide with each other, grinding and
chipping each other, progressively becoming smaller, smoother and rounder. Scree also collides with the base of the
cliff face, chipping small pieces of rock from the cliff or have a corrasion (abrasion) effect, similar to sandpapering.
Coastal erosion
40
Corrasion
Corrasion (abrasion) occurs when waves break on cliff faces and slowly erode it. As the sea pounds cliff faces it
also uses the scree from other wave actions to batter and break off pieces of rock from higher up the cliff face which
can be used for this same wave action and attrition.
Corrosion
Corrosion or solution/chemical weathering occurs when the sea's pH (anything below pH 7.0) corrodes rocks on a
cliff face. Limestone cliff faces, which have a high pH, are particularly affected in this way. Wave action also
increases the rate of reaction by removing the reacted material.
Factors that influence erosion rates
Primary factors
The ability of waves to cause erosion of the cliff face depends many factors.
The hardness or ‘erodibility’ of sea-facing rocks is controlled by the rock strength and the presence of fissures,
fractures, and beds of non-cohesive materials such as silt and fine sand.
The rate at which cliff fall debris is removed from the foreshore depends on the power of the waves crossing the
beach. This energy must reach a critical level to remove material from the debris lobe. Debris lobes can be very
persistent and can take many years to completely disappear.
Beaches dissipate wave energy on the foreshore and provide a measure of protection to the adjoining land.
The stability of the foreshore, or its resistance to lowering. Once stable, the foreshore should widen and become
more effective at dissipating the wave energy, so that fewer and less powerful waves reach beyond it. The provision
of updrift material coming onto the foreshore beneath the cliff helps ensure a stable beach.
The adjacent bathymetry controls the wave energy arriving at the coast, and can have an important influence on the
rate of cliff erosion.
Coastal Erosion
Pacifica, California coast after
major storms in 1997 destroyed
the houses shown above.
Beach erosion at Cabrillo
National Monument,
California.
Large-scale coastal erosion
at Torrey Pines State
Reserve, California.
Coastal erosion at Torrey
Pines State Reserve,
California, resulted in the
necessary relocation of a
scenic overlook.
Coastal erosion
Secondary factors
•
•
•
•
•
•
Weathering and transport slope processes
Slope hydrology
Vegetation
Cliff foot erosion
Cliff foot sediment accumulation
Resistance of cliff foot sediment to attrition and transport
Tertiary factors
• Resource extraction
• Coastal management
See also
•
•
•
•
•
•
•
•
•
•
Beach nourishment
Bioerosion
Blowhole
Coastal and Estuarine Research Federation (CERF)
Coastal and oceanic landforms
Coastal management
Erosion
Modern recession of beaches
Natural arch
Submersion
External links
•
•
•
•
•
•
•
•
•
•
•
Sustainable coastal erosion management in Europe [1]
Coastal Erosion Information from the Coastal Ocean Institute [2], Woods Hole Oceanographic Institution
Environment Agency guide to coastal erosion [3]
Wave Erosion [4]
Time-lapse movie of beach erosion in Australia [5]
Examine an example of wave erosion [6]
Erosion & Flooding in the Parish of Easington [7]
Some interesting teaching resources [8]
Examples of coastal landforms [9]
US Economic Costs of Coastal Erosion & Inundation [10] NOAA Economics
British Geological Survey coastal erosion and landslides case studies [11]
Images:
• Work to reduce coastal erosion at Lyme Regis in Dorset 2006 [12]
• Images of Coastal features [13]
41
Coastal erosion
42
References
[1] http:/ / www. eurosion. org
[2] http:/ / www. whoi. edu/ page. do?pid=11914
[3] http:/ / www. environment-agency. gov. uk/ homeandleisure/ 107495. aspx
[4] http:/ / cse. cosm. sc. edu/ erth_sci/ Coasts/ Erode. htm
[5] http:/ / www. youtube. com/ watch?v=LN_0LM1XtbU
[6] http:/ / www. classzone. com/ books/ earth_science/ terc/ content/ visualizations/ es1606/ es1606page01. cfm?chapter_no=visualization
[7] http:/ / www. hull. ac. uk/ coastalobs/ easington/ erosionandflooding/
[8] http:/ / www. geolsoc. org. uk/ template. cfm?name=resources
[9] http:/ / www. fettes. com/ caithness/ coastal%20erosion. htm
[10] http:/ / www. economics. noaa. gov/ ?goal=weather& file=events/ erosion/
[11] http:/ / www. bgs. ac. uk/ research/ climatechange/ environment/ coastal/ caseStudies. html
[12] http:/ / www. malconet. me. uk/ lymebeach
[13] http:/ / www. earthscienceworld. org/ images/ search/ results. html?Keyword=Sea%20Stacks#null
Wave-cut platform
A wave-cut platform, or shore platform is the narrow flat area often found at the base
of a sea cliff or along the shoreline of a lake, bay, or sea that was created by the action of
waves. Wave-cut platforms are often most obvious at low tide when they become visible
as huge areas of flat rock. Sometimes the landward side of the platform is covered by
sand, forming the beach, and then the platform can only be identified at low tides or
when storms move the sand.
Formation
It forms after destructive waves hit against the cliff face, causing undercutting between
the high and low water marks, mainly as a result of corrasion and hydraulic power,
creating a wave-cut notch. This notch then enlarges into a cave. The waves undermine
this portion until the roof of the cave cannot hold due to the pressure and freeze-thaw
weathering acting on it, and collapses, resulting in the cliff retreating landward. The base
of the cave forms the wave-cut platform as attrition causes the collapsed material to be
broken down into smaller pieces, while some cliff material may be washed into the sea.
This may be deposited at the end of the platform, forming an off-shore terrace.
Because of the continual wave action, a wave-cut platform represents an extremely
hostile environment and only the toughest of organisms can utilize such a niche.
The formation of a wave
cut platform
Wave-cut platform
43
Use of ancient examples
Ancient wave-cut platforms provide evidence of past
sea and lake levels. Raised and abandoned platforms,
sometimes found behind modern beaches, are evidence
of higher sea levels in the geological past[1] , and have
been used to identify areas of isostatic adjustment. By
using scientific dating methods, or examination of
marine fossils found on the platform, it is possible to
work out when the platform was formed, thus giving
geographers and geologists information about sea
levels at known times in the past. This has been used in
the United Kingdom and other previously glaciated
areas to calculate the rate at which land is rising now
that it is no longer covered in ice.
Wave-cut platform at Southerndown, South Wales
Where the coastline itself is changing due to seismic
action, there may be a series of platforms showing
earlier sea levels and indicating the amount of uplift
caused by various earthquakes.
Usage of term 'wave-cut'
According to Trenhaile [2] and Sunamura [3] , "the term
'Wave Cut Platform' should no longer be used as it
assumes that shore platforms are the result of wave
action, which is not always true. Shore Platforms are
clearly erosional features that develop when erosion of
a rocky coast and the subsequent removal of the debris
by waves and currents leave behind the erosional
surface".[4]
References
Raised beach and wave-cut platform, Bleik, Andøya, Norway
Wave-cut platforms from Lake Bonneville (Pleistocene) preserved
on Antelope Island, Great Salt Lake, Utah.
[1] Wilson, M.A., Curran, H.A. and White, B. 1998: Paleontological
evidence of a brief global sea-level event during the last interglacial. Lethaia 31: 241-250. (http:/ / www3. wooster. edu/ geology/
WilsonEtAl98. pdf)
[2] Trenhaile, A. S. 1987: The Geomorphology of Rock Coasts. (Oxford University Press, Oxford, U.K.) 393 pp.
[3] Sunamura, T., 1992. Geomorphology of rocky coasts. New York: John Wiley.
[4] Masselink, G and Hughes, M. 2003. Introduction to Coastal Processes and Geomorphology. Hodder Arnold
See also
•
•
•
•
•
•
Beach
Bench (geology)
Landform
Machair
Marine terrace
Raised beach
Wave-cut platform
• Raised shorelines
• Terrace (geology)
Lagoon
A lagoon is a body of shallow sea water or brackish water separated from the sea by some form of barrier.
Definition
The body of comparatively shallow salt or brackish
water is separated from the deeper sea by a shallow or
exposed barrier beach, sandbank of marine origin, coral
reef, or similar feature.[1] Thus, the enclosed body of
water behind a barrier reef or barrier islands or
enclosed by an atoll reef is called a lagoon. When used
within this context of a distinctive portion of coral reef
ecosystems, the term "lagoon" is synonymous with the
term "back reef" or "backreef", which is more
commonly used by coral reef scientists to refer to the
same area.[2]
These applications of lagoon in English dates from
1769. It adapted and extended the sense of the Venetian
laguna (cf Latin lacuna, ‘empty space’), which
specifically
referred
to
Venice’s
shallow,
island-studded stretch of saltwater, protected from the
Garabogaz-Göl lagoon in Turkmenistan.
Adriatic by the barrier beaches of the Lido (see
Venetian Lagoon). Lagoon refers to both coastal lagoons formed by the build-up of sandbanks or reefs along shallow
coastal waters, and the lagoons in atolls, formed by the growth of coral reefs on slowly sinking central islands.
Lagoons that are fed by freshwater streams are also called estuaries.
Many lagoons do not include "lagoon" in their common names. Albemarle Sound in North Carolina, Great South
Bay, between Long Island and the barrier beaches of Fire Island in New York; Isle of Wight Bay, which separates
Ocean City, Maryland from the rest of Worcester County, Maryland; Banana River in Florida; and Lake Illawarra in
New South Wales are all lagoons, despite their names. In the UK there are lagoons at Montrose Basin, (Scotland)
and Broad Water near Tywyn, (Wales), whilst the expanse of water inside Chesil Beach, England, known as The
Fleet, could also be described as a lagoon. There is also one near the small town of Dingle in Western Ireland. Some
of the famous lagoons in India are the Chilika Lake in Orissa, near Puri, and the Vembanad Lake in Kerala. Both are
connected to the Bay of Bengal and the Arabian Sea respectively through a narrow channel. Some other known
lagoons like in Africa, include the Lagos Lagoon which empties itself into the Gulf of Guinea and the South Atlantic
Ocean [Keta Lagoon in Ghana.
The biggest lagoon in the world is located in New Caledonia.
In Latin America often the use of “laguna”, which lagoon translates to, is used to describe a lake, such as Laguna
Catemaco.
44
Lagoon
45
Images
Glenrock Lagoon in Australia
Lagoa dos Patos
lagoon in Brazil
Venetian Lagoon as
seen by Landsat 1
Vistula and Curonian lagoons
on the Baltic Sea.
Nearly half the area of
Kiritimati is covered with
lagoons, some freshwater and
some seawater.
Blue lagoon, Ölüdeniz, Turkey
Szczecin Lagoon as seen by
Landsat c. 2000.
See also
•
•
•
•
•
•
List of lagoons by area
Aerated lagoon
Anaerobic lagoon
Ayre (landform)
Kerala backwaters
Estuary
Notes
[1] Reid (1961) p.73
[2] Aronson 1993
References
• Reid, George K. (1961). Ecology of Inland Waters and Estuaries. New York: Van Nostrand Reinhold Company.
• Aronson, R.B. (1993). "Hurricane effects on backreef echinoderms of the Caribbean". Coral Reefs.
Estuary
46
Estuary
An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a
free connection to the open sea.[1]
Estuaries form a transition zone between river environments and ocean environments and are subject to both marine
influences, such as tides, waves, and the influx of saline water; and riverine influences, such as flows of fresh water
and sediment. The inflow of both seawater and freshwater provide high levels of nutrients in both the water column
and sediment, making estuaries among the most productive natural habitats in the world.[2]
Most modern-day estuaries were formed during the Holocene epoch by the flooding of river-eroded or
glacially-scoured valleys when sea level began to rise about 10,000-12,000 years ago.[3] Estuaries are typically
classified by their geomorphological features or by water circulation patterns and can be referred to by many
different names, such as bays, harbors, lagoons, inlets, or sounds, although sometimes these water bodies do not
necessarily meet the above criteria of an estuary and may be fully saline.
Estuaries are amongst the most heavily populated areas throughout the world, with about 60% of the world’s
population living along estuaries and the coast. As a result, estuaries are suffering degradation by many factors,
including sedimentation from soil erosion from deforestation; overgrazing and other poor farming practices;
overfishing; drainage and filling of wetlands; eutrophication due to excessive nutrients from sewage and animal
wastes; pollutants including heavy metals, PCBs, radionuclides and hydrocarbons from sewage inputs; and diking or
damming for flood control or water diversion.[3]
Definition
The word “estuary” is derived from the Latin word aestuarium meaning
tidal inlet of the sea, which in itself is derived from the term aestus,
meaning tide. There have been many definitions proposed to describe
an estuary. The most widely accepted definition is: “a semi-enclosed
coastal body of water, which has a free connection with the open sea,
and within which sea water is measurably diluted with freshwater
derived from land drainage.” [1] However, this definition excludes a
number of coastal water bodies such as coastal lagoons and brackish
seas. A more thorough definition of an estuary would be “a
semi-enclosed body of water connected to the sea as far as the tidal
limit or the salt intrusion limit and receiving freshwater runoff;
however the freshwater inflow may not be perennial, the connection to
the sea may be closed for part of the year and tidal influence may be
negligible.” [3] This definition includes classical estuaries as well as
fjords, lagoons, river mouths, and tidal creeks. Estuaries are a dynamic
ecosystem with a connection with the open sea through which the
seawater enters accordingly to the rhythm of the tides. The seawater
entering the estuary is diluted by the freshwater flowing from rivers
and streams. The pattern of dilution varies in different estuaries and is
dependent on the volume of freshwater, tidal amplitude range, and the
extent of evaporation from the water within the estuary. [2]
River Exe estuary
River Nith estuary
Estuary
47
Classification based on geomorphology
Drowned river valleys
Many drowned river valley estuaries were formed between about
15,000 and 6000 years ago following the end of the Wisconsin (or
'Devensian') glaciation when a eustatic rise in sea level of 100 m to 130
m, flooded river valleys that were cut into the landscape when sea level
was lower, creating the estuarine systems. Additionally, the general
subsidence of coastal regions contributed to the development of
drowned river valleys. Well developed drowned river valleys are
generally found on coastlines with low, wide coastal plains. Their
width-to-depth ratio is typically large, appearing wedge-shaped in the
inner part and broadening and deepening seaward. Water depths rarely
exceed 30 meters. Examples of this type of estuary include the
Chesapeake Bay and Delaware Bay, along the U.S. mid-Atlantic coast,
and along the U.S. Gulf coast, Galveston Bay and Tampa Bay[4] .
Estuary mouth located in Darwin, Northern
Territory, Australia
Lagoon-type or bar-built
These estuaries are semi-isolated from ocean waters by barrier beaches
(barrier islands and barrier spits). Formation of barrier beaches
partially encloses the estuary with only narrow inlets allowing contact
with the ocean waters. Bar-built estuaries typically develop on gently
sloping plains located along tectonically stable edges of continents and
marginal sea coasts. They are extensive along the Atlantic and Gulf
coasts of the U.S. in areas with active coastal deposition of sediments
and where tidal ranges are less than 4 meters. The barrier beaches that
enclose bar-built estuaries have been developed in several ways: 1)
upbuilding of offshore bars from wave action, in which sand from the
seafloor is deposited in elongate bars parallel to the shoreline, 2)
reworking of sediment discharge from rivers by wave, current, and
wind action into beaches, overwash flats, and dunes, 3) engulfment of
mainland beach ridges (ridges developed from the erosion of coastal
plain sediments approximately 5,000 years ago) due to sea level rise
and resulting in the breaching of the ridges and flooding of the coastal
lowlands, forming shallow lagoons, 4) elongation of barrier spits from
the erosion of headlands, with the spit growth occurring in the
direction of the littoral drift due to the action of longshore currents.
Barrier beaches form in shallow water and are generally parallel to the
shoreline, resulting in long, narrow estuaries. The average water depth
is usually less than 5 m, and rarely exceed 10 m. Examples of bar-built
estuaries include Barnegat Bay, New Jersey, Laguna Madre, Texas,
and Pamlico Sound, North Carolina.
Estuary mouth
Río de la Plata estuary
Estuary mouth of the Yachats River in Yachats,
Oregon
Estuary
Fjord-type
Fjord type estuaries are formed in deeply eroded valleys formed by
glaciers. These U-shaped estuaries typically have steep sides, rock
bottoms, and underwater sills contoured by glacial movement. The
shallowest area of the estuary occurs at the mouth, where terminal
glacial deposits or rock bars form sills that restrict water flow. In the
upper reaches of the estuary, the depth can exceed 300 meters. The
width-to-depth ratio is generally small. When estuaries contain very
Amazon estuary
shallow sills, tidal oscillations only affect near surface waters to sill
depth, and waters below sill depth may remain stagnant for very long periods of time, resulting in only an occasional
exchange of the deep water of the estuary with the ocean. If the sill depth is deep, water circulation is less restricted
and a slow, but steady exchange of water from the estuary and the ocean occur. Fjord-type estuaries can be found
along the coasts of Alaska, eastern Canada, Greenland, Iceland, New Zealand, and Norway.
Tectonically produced
These estuaries are formed by subsidence or land cut off from the ocean by land movement associated with faulting,
volcanoes, and landslides. Inundation from eustatic sea level rise during the Holocene Epoch has also contributed to
the formation of these estuaries. There are only a small number of tectonically produced estuaries; one example is
the San Francisco Bay, which was formed by the crustal movements of the San Andreas fault system causing the
inundation of the lower reaches of the Sacramento and San Joaquin rivers.[5]
Classification based on water circulation
Salt wedge
In this type of estuary, river output greatly exceeds marine input and tidal effects have a minor importance. Fresh
water floats on top of the seawater in a layer that gradually thins as it moves seaward. The denser seawater moves
landward along the bottom of the estuary, forming a wedge-shaped layer that is thinner as it approaches land. As a
velocity difference develops between the two layers, shear forces generate internal waves at the interface, mixing the
seawater upward with the freshwater. An example of a salt wedge estuary is the Mississippi River. [5]
Partially mixed
As tidal forcing increases, river output becomes less than the marine input. Here, current induced turbulence causes
mixing of the whole water column such that salinity varies more longitudinally rather than vertically, leading to a
moderately stratified condition. Examples include the Chesapeake Bay and Narragansett Bay. [5]
Vertically homogenous
Tidal mixing forces exceed river output, resulting in a well mixed water column and the disappearance of the vertical
salinity gradient. The freshwater-seawater boundary is eliminated due to the intense turbulent mixing and eddy
effects. The lower reaches of the Delaware Bay and the Raritan River in New Jersey are examples of vertically
homogenous estuaries. [5]
48
Estuary
Inverse
Inverse estuaries occur in dry climates where evaporation greatly exceeds the inflow of fresh water. A salinity
maximum zone is formed, and both riverine and oceanic water flow close to the surface towards this zone.[6] This
water is pushed downward and spreads along the bottom in both the seaward and landward direction. [3] An example
of an inverse estuary is Spencer Gulf, South Australia.
Intermittent
Estuary type varies dramatically depending on freshwater input, and is capable of changing from a wholly marine
embayment to any of the other estuary types. [7] [8]
(See also Estuarine water circulation)
Implications for marine life
Estuaries provide habitats for a large number of organisms and support very high productivity. Estuaries provide
habitats for many fish nurseries, depending upon their locations in the world, such as salmon and sea trout[9] . Also,
migratory bird populations, such as the black-tailed godwit, Limosa limosa islandica[10] make essential use of
estuaries.
Two of the main challenges of estuarine life are the variability in salinity and sedimentation. Many species of fish
and invertebrates have various methods to control or conform to the shifts in salt concentrations and are termed
osmoconformers and osmoregulators. Many animals also burrow to avoid predation and to live in the more stable
sedimental environment. However, large numbers of bacteria are found within the sediment which have a very high
oxygen demand. This reduces the levels of oxygen within the sediment often resulting in partially anoxic conditions,
which can be further exacerbated by limited water flux.
Plankton are key primary producers in estuaries. They move with the water bodies and can be flushed in and out with
the tides. Their productivity is largely dependant upon the turbidity of the water. The main plankton present are
diatoms and dinoflagellates which are abundant in the sediment.
It is important to remember that a primary source of food for many organisms on estuaries, including bacteria, is
detritus from the settlement of the sedimentation.
Human impacts
Of the 32 largest cities in the world, 22 are located on estuaries.[11] For example, New York City is located at the
orifice of the Hudson River estuary.[12]
As ecosystems, estuaries are under threat from human activities such as pollution and overfishing. They are also
threatened by sewage, coastal settlement, land clearance and much more. Estuaries are affected by events far
upstream, and concentrate materials such as pollutants and sediments[13] . Land run-off and industrial, agricultural,
and domestic waste enter rivers and are discharged into estuaries. Contaminants can be introduced which do not
disintegrate rapidly in the marine environment, such as plastics, pesticides, furans, dioxins, phenols and heavy
metals.
Such toxins can accumulate in the tissues of many species of aquatic life in a process called bioaccumulation. They
also accumulate in benthic environments, such as estuaries and bay muds: a geological record of human activities of
the last century.
For example, Chinese and Russian industrial pollution, such as phenols and heavy metals, in the Amur River have
devastated fish stocks and damaged its estuary soil.[14]
Estuaries tend to be naturally eutrophic because land runoff discharges nutrients into estuaries. With human
activities, land run-off also now includes the many chemicals used as fertilizers in agriculture as well as waste from
49
Estuary
50
livestock and humans. Excess oxygen depleting chemicals in the water can lead to hypoxia and the creation of dead
zones.[15] It can result in reductions in water quality, fish, and other animal populations.
Overfishing also occurs. Chesapeake Bay once had a flourishing oyster population which has been almost wiped out
by overfishing. Historically the oysters filtered the estuary's entire water volume of excess nutrients every three or
four days. Today that process takes almost a year,[16] and sediment, nutrients, and algae can cause problems in local
waters. Oysters filter these pollutants, and either eat them or shape them into small packets that are deposited on the
bottom where they are harmless.
Notable examples
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Albemarle Sound
Amazon River
The Golden Horn
Chesapeake Bay
Delaware Bay
Gulf of Saint Lawrence
Humber
Laguna Madre
Lake Pontchartrain
Long Island Sound
Mobile Bay
Narragansett Bay
New York Harbor
Ob River
Puget Sound
Pamlico Sound
Rio de la Plata
San Francisco Bay
Thames Estuary
See also
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Bay mud
Brackish water
Coastal and Estuarine Research Federation
Estuaries and Coasts
Estuarine fish
Firth
Liman
List of waterways
National Estuarine Research Reserve
Region of freshwater influence
Ria
River delta
Tidal bore
Tidal prism
Estuary
References
[1] Pritchard, D. W. (1967) What is an estuary: physical viewpoint. p. 3–5 in: G. H. Lauf (ed.) Estuaries, A.A.A.S. Publ. No. 83, Washington,
D.C.
[2] McLusky, D.S. and Elliott, M. (2004) "The Estuarine Ecosystem: ecology, threats and management." New York: Oxford University Press
Inc. ISBN 0-19-852508-7
[3] Wolanski, E. (2007) "Estuarine Ecohydrology." Amsterdam, The Netherlands: Elsevier. ISBN 978-0-444-53066-0
[4] Kunneke, J.T., and T.F. Palik, 1984. "Tampa Bay environmental atlas", U.S. Fish Wildl. Serv. Biol. Rep. 85(15) (http:/ / www. nwrc. usgs.
gov/ wdb/ pub/ others/ 85_15. pdf), page 3. Retrieved January 12, 2010.
[5] Kennish, M.J. (1986) "Ecology of Estuaries. Volume I: Physical and Chemical Aspects." Boca Raton, FL: CRC Press, Inc. ISBN:
0-8493-5892-2
[6] Wolanski, E. (1986). "An evaporation-driven salinity maximum zone in Australian tropical estuaries" Estuarine, Coastal, and Shelf Science
22, 415-424.
[7] Tomczak, M (2000) " Oceanography Notes Ch. 12: Estuaries (http:/ / www. es. flinders. edu. au/ ~mattom/ IntroOc/ notes/ lecture12. html).
Retrieved 30 November 2006.
[8] Day, J.H. (1981) "Estuarine Ecology." Rotterdam, The Netherlands: A.A. Balkema. ISBN: 90-6191-205-9.
[9] Bronwyn M. Gillanders, Evidence of connectivity between juvenile and adult habitats for mobile marine fauna: an important component of
nurseries (http:/ / www. int-res. com/ articles/ meps2003/ 247/ m247p281. pdf). 2003. Marine Ecology Progress Series
[10] Jennifer A. Gill, The buffer effect and large-scale population regulation in migratory birds (http:/ / www. nature. com/ nature/ journal/ v412/
n6845/ abs/ 412436a0. html). 2001. Nature 412, 436-438
[11] Ross, D A (1995) Introduction to Oceanography. New York: Harper Collins College Publishers. ISBN 978-0-673-46938-0
[12] NOAA Estuaries tutorial (http:/ / oceanservice. noaa. gov/ education/ kits/ estuaries/ media/ supp_estuar00c. html) Revised March 25, 2008
[13] G.Branch, Estuarine vulnerability and ecological impacts, TREE vol. 14, no. 12 Dec. 1999
[14] "Indigenous Peoples of the Russian North, Siberia and Far East: Nivkh" (http:/ / www. npolar. no/ ansipra/ english/ Indexpages/
Ethnic_groups. html#19) by Arctic Network for the Support of the Indigenous Peoples of the Russian Arctic]
[15] Gerlach: Marine Pollution, Springer, Berlin (1975)
[16] "Oyster Reefs: Ecological importance" (http:/ / habitat. noaa. gov/ restorationtechniques/ public/ habitat. cfm?HabitatID=2&
HabitatTopicID=11). US National Oceanic and Atmospheric Administration. . Retrieved 2008-01-16.
External links
• Animated documentary on Chesapeake Bay (http://ecopath.org/LifeInTheChesapeakeBay/) NOAA.
• "Habitats: Estuaries - Characteristics" (http://www.onr.navy.mil/Focus/ocean/habitats/estuaries1.htm).
www.onr.navy.mil. Retrieved 2009-11-17
• The Estuary Guide (Based on experience and R&D within the UK) (http://www.estuary-guide.net).
bjn:Muhara
51
River delta
52
River delta
A delta is a landform that is formed at the mouth of a river where that
river flows into an ocean, sea, estuary, lake, reservoir, flat arid area, or
another river. Deltas are formed from the deposition of the sediment
carried by the river as the flow leaves the mouth of the river. Over long
periods of time, this deposition builds the characteristic geographic
pattern of a river delta.
The Greek historian Herodotus coined the term delta for the Nile River
delta because the sediment deposited at its mouth had the shape of the
upper-case Greek letter Delta: Δ.
Nile River delta, as seen from Earth orbit. The
Nile is an example of a wave-dominated delta
that has the classic Greek delta (Δ) shape after
which River deltas were named. Photo courtesy
of NASA.
Delta formation
River deltas form when a river carrying sediment reaches a body
of standing water,such as a lake, ocean,or reservoir. When the
flow enters the standing water, it is no longer confined to its
channel and expands in width. This flow expansion results in a
decrease in the flow velocity, which diminishes the ability of the
flow to transport sediment. As a result, sediment drops out of the
flow and deposits. Over time, this single channel will build a
deltaic lobe (such as the bird's-foot of the Mississippi or Ural
River deltas), pushing its mouth further into the standing water. As
A small-scale alluvial fan delta, Death Valley National
the deltaic lobe advances, the gradient of the river channel
Park, California, USA. This alluvial fan delta is steep
becomes lower because the river channel is longer but has the
and, for the small-scale flows it experiences, has
sediment with a large grain size (the sand scales to
same change in elevation (see slope). As the slope of the river
boulders for large-scale deltas). Footprints for scale.
channel decreases, it becomes unstable for two reasons. First,
Note the many dry river channels and fan-like shape.
water under the force of gravity will tend to flow in the most direct
course down slope. If the river could breach its natural levees (i.e.,
during a flood), it would spill out onto a new course with a shorter route to the ocean, thereby obtaining a more
stable steeper slope.[1] Second, as its slope gets lower, the amount of shear stress on the bed will decrease, which will
result in deposition of sediment within the channel and for the channel bed to rise relative to the floodplain. This will
make it easier for the river to breach its levees and cut a new channel that enters the body of standing water at a
steeper slope. Often when the channel does this, some of its flow can remain in the abandoned channel. When these
channel switching events happen repeatedly over time, a mature delta will gain a distributary network.
Another way in which these distributary networks may form is from the deposition of mouth bars (mid-channel sand
and/or gravel bars at the mouth of a river). When this mid-channel bar is deposited at the mouth of a river, the flow is
River delta
53
routed around it. This results in additional deposition on the upstream end of the mouth-bar, which splits the river
into two distributary channels. A good example of the result of this process is the Wax Lake Delta in Louisiana.
In both of these cases, depositional processes force redistribution of deposition from areas of high deposition to areas
of low deposition. This results in the smoothing of the planform (or map-view) shape of the delta as the channels
move across its surface and deposit sediment. Because the sediment is laid down in this fashion, the shape of these
deltas approximates a fan. It is closer to an ideal fan the more often the flow changes course because more rapid
changes in channel position results in more uniform deposition of sediment on the delta front. The Mississippi and
Ural River deltas, with their bird's-feet, are examples of rivers that do not avulse often enough to form a symmetrical
fan shape. Alluvial fan deltas, as seen in their name, avulse frequently and more closely approximate an ideal fan
shape.
Types of deltas
Deltas are typically classified according to the main control on
deposition, which is usually either a river, waves, or tides.[2] These
controls have a large effect on the shape of the resulting delta.
River-dominated deltas
River dominated deltas, such as the Mississippi River Delta, usually
take on a multi-lobed shape that results from repeated sequences of
Delta lobe switching in the Mississippi Delta,
channel occupation, offshore deposition, and channel avulsion. (See
4600 yrs BP, 3500 yrs BP, 2800 yrs BP, 1000 yrs
delta switching.) When a single channel is occupied for a long period
BP, 300 yrs BP, 500 yrs BP, current
of time, its deposits extend the channel far offshore, and causes the
delta to resemble a bird's foot; the term "digitate delta" is sometimes used as well. These deltas are often
characterized by a main channel that divides itself into several distributary channels.
Digitate deltas can be often seen on sediment-rich rivers flowing into
lakes. Among the examples are the delta of the Ural River in
Kazakhstan (46°53′N 51°37′E),[3] the delta of Saskatchewan River at
its fall into Cedar Lake in Manitoba,[4] or the Mitchell River silt jetties
at the fall of the Mitchell River into Lake King (part of Australia's
Gippsland Lakes).
The "bird's-foot" delta of the Ural River
Smaller formation of this type can be seen on rivers and irrigation
channels depositing sediment into human-built reservoirs. One
example is the sediment-formed peninsula at the point (45°27′50″N
44°37′33″E) where the Kuma–Manych Canal flows into the Chogray
Reservoir in southern Russia. As these structures were completed in
the late 1960s, the peninsula must be the product of just 40 years'
worth of sedimentation.
River delta
54
Wave-dominated deltas
In wave dominated deltas, wave erosion controls the shape of the delta, although deposition still outweighs the
amount of erosion and the delta is able to advance into the sea. Deltas of this form, such as the Nile Delta, tend to
have a characteristic Greek-capital-delta shape
.
Tide-dominated deltas
Erosion is also an important control in tide dominated deltas, such as
the Ganges Delta, which may be mainly submarine, with prominent
sand bars and ridges. This tends to produce a "dendritic" structure.[2]
Tidal deltas behave differently from river- and wave-dominated deltas,
which tend to have a few main distributaries. Once a wave- or riverdistributary silts up, it is abandoned, and a new channel forms
elsewhere. In a tidal delta, new distributaries are formed during times
when there's a lot of water around - such as floods or storm surges.
These distributaries slowly silt up at a pretty constant rate until they
fizzle out.[2]
Gilbert deltas
The Ganges Delta in India and Bangladesh is the
largest delta in the world and it is also one of the
most fertile regions in the world.
A Gilbert delta (named after Grove Karl Gilbert) is a specific type of
delta that is formed by coarse sediments, as opposed to gently-sloping muddy deltas such as that of the Mississippi.
For example, a mountain river depositing sediment into a freshwater lake would form this kind of delta.[5] [6] While
some authors describe both lacustrine and marine locations of Gilbert deltas[5] , others note that their formation is
more characteristic of the freshwater lakes, where it is easier for the river water to mix with the lakewater faster (as
opposed to the case of a river falling into the sea or a salt lake, where less dense fresh water brought by the river
stays on top longer).[7]
G.K. Gilbert himself first described this type of delta on Lake Bonneville in 1885.[7] Elsewhere, similar structures
can be found e.g. at the mouths of several creeks flowing into Okanagan Lake in British Columbia and forming
prominent peninsulas at Naramata (49°35′30″N 119°35′30″W), Summerland (49°34′23″N 119°37′45″W), or
Peachland (49°47′00″N 119°42′45″W)
Estuaries
Other rivers, particularly those located on coasts with significant tidal range, do not form a delta but enter into the
sea in the form of an estuary. Notable examples include the Saint Lawrence River and the Tagus estuary.
Inland deltas
River delta
55
In rare cases the river delta is located inside a large valley and is called
an inverted river delta. Sometimes a river will divide into multiple
branches in an inland area, only to rejoin and continue to the sea; such
an area is known as an inland delta, and often occur on former lake
beds. The Inner Niger Delta is the most notable example. The Amazon
has also an inland delta before the island of Marajó.
In some cases a river flowing into a flat arid area splits into channels
which then disappear in the desert. Okavango Delta in Botswana is one
well-known example.
Okavango Delta
Sedimentary structure
The formation of a delta consists of three main forms: the topset, foreset/frontset, and bottomset.[5]
• The bottomset beds are created from the suspended sediment that settles out of the water as the river flows into
the body of water and loses energy. The suspended load is carried out the furthest into the body of water than all
other types of sediment creating a turbidite. These beds are laid down in horizontal layers and consist of smaller
grains.
• The foreset beds in turn build over the bottomset beds as the main delta form advances. The foreset beds consist
of the bed load that the river is moving along which consists of larger sediments that roll along the main channel.
When it reaches the edge of the form, the bed load rolls over the edge, and builds up in steeply angled layers over
the top of the bottomset beds. The angle of the outermost edge of the delta is created by the sediments angle of
repose. As the forsets build outward (which make up the majority of the delta) they pile up and miniature
landslides occur. This slope is created in this fashion as the bedload continues to be deposited and the delta moves
outward. In cross section, one would see the foresets lying in angled, parallel bands, showing each stage of the
creation of the delta.
• The topset beds in turn overlay the foresets, and are horizontal layers of smaller sediment size that form as the
main channel of the river shifts elsewhere and the larger particles of the bed load no longer are deposited. As the
channels move across the top of the delta, the suspended load settles out in horizontal beds over the top.
Deltas and alluvial fans
Deltas are differentiated from alluvial fans in that deltas have a shallow slope, contain fine-grained sediment (sand
and mud), and always flow into a body of water. Alluvial fans, on the other hand, are steep, have coarse-grained
sediments (including boulders), and are dominated by debris flows and large floods; these floods are often flash
floods. They can either flow onto a land surface, or into a body of water; in the latter case, they are called alluvial fan
deltas.
Examples of notable deltas
The most famous delta is that of the Nile River, and it is this delta from which the term is derived. The
Ganges/Brahmaputra combination delta spans most of Bangladesh and West Bengal, empties into the Bay of Bengal
and is the world's largest delta. Other rivers with notable deltas include, the Fly River, the Niger River, the
Tigris-Euphrates, the Rhine, the Po, the Rhône, the Danube, the Ebro, the Volga, the Lena, the Indus, the Mahanadi,
the Krishna-Godavari, the Kaveri, the Ayeyarwady (Irrawaddy), the Mekong, the Huanghe, the Yangtze, the
Sacramento-San Joaquin, the Mississippi, the Orinoco, and the Paraná.
River delta
56
Ecological threats to deltas
Human activities, including diversion of water and the creation of dams for hydroelectric power or to create
reservoirs can radically alter delta ecosystems. Dams block sedimentation which can cause the delta to erode away.
The use of water upstream can greatly increase salinity levels as less fresh water flows to meet the salty ocean water.
While nearly all deltas have been impacted to some degree by humans, the Nile Delta and Colorado River Delta are
some of the most extreme examples of the ecological devastation caused to deltas by damming and diversion of
water.
Deltas on Mars
Researchers have found a number of examples of deltas that formed in Martian lakes. Finding deltas is a major sign
that Mars once had a lot of water. Deltas have been found over a wide geographical range. Below, are pictures of a
few.[8]
Delta in Ismenius Lacus
quadrangle, as seen by THEMIS.
Delta in Lunae Palus
quadrangle, as seen by
THEMIS.
Delta in Margaritifer Sinus
quadrangle as seen by
THEMIS.
Probable delta in a
crater to the NE of
Holden Crater, as
seen by Mars Global
Surveyor. Image in
Margaritifer Sinus
quadrangle.
See also
•
•
•
•
•
Estuary
Mega delta
Alluvial fan
Formation of delta-shaped river basin
Avulsion (river)
References
[1] Slingerland, R. and N. D. Smith (1998), Necessary conditions for a meandering-river avulsion, Geology (Boulder), 26, 435-438.
[2] Fagherazzi, S (Dec 2008). "Self-organization of tidal deltas" (http:/ / www. pubmedcentral. nih. gov/ articlerender. fcgi?tool=pmcentrez&
artid=2596246). Proceedings of the National Academy of Sciences of the United States of America 105 (48): 18692–5.
doi:10.1073/pnas.0806668105. ISSN 0027-8424. PMID 19033190. PMC 2596246.
[3] Ural River Delta, Kazakhstan (http:/ / earthobservatory. nasa. gov/ IOTD/ view. php?id=5551) (NASA Earth Observatory)
[4] Saskatchewan River Delta, Manitoba, Canada (http:/ / earthobservatory. nasa. gov/ IOTD/ view. php?id=8167) (NASA Earth Observatory)
[5] Characteristics of deltas (http:/ / www. maine. gov/ doc/ nrimc/ mgs/ explore/ surficial/ facts/ dec03. htm). (Available archived at (http:/ /
web. archive. org/ web/ 20061012185632/ http:/ / www. maine. gov/ doc/ nrimc/ mgs/ explore/ surficial/ facts/ dec03. htm) - checked Dec
2008.)
[6] Bernard Biju-Duval, J. Edwin Swezey. "Sedimentary Geology". Page 183. ISBN 2710808021. Editions TECHNIP, 2002. Partial text (http:/ /
books. google. com. au/ books?id=2txTeLt5MXgC) on Google Books.
[7] "Geological and Petrophysical Characterization of the Ferron Sandstone for 3-D Simulation of a Fluvial-deltaic Reservoir". By Thomas C.
Chidsey, Thomas C. Chidsey, Jr (ed), Utah Geological Survey, 2002. ISBN 1557916683. Page 2-17. Partial text (http:/ / books. google. com.
au/ books?id=jacORXGQG9AC) on Google Books.
[8] Irwin III, R. et al. 2005. An intense terminal epoch of widespread fluvial activity on early Mars: 2. Increased runoff and paleolake
development. Journal of Geophysical Research: 10. E12S15
River delta
External links
• Louisiana State University Geology (http://www.geol.lsu.edu/WDD/DELTA_LISTS/continents.htm) World Deltas
57
58
Ports & Harbours
Harbor
A harbor or harbour (see spelling differences), or haven, is a place where ships, boats, and barges can seek shelter
from stormy weather, or else are stored for future use. Harbors can be natural or artificial. An artificial harbor has
deliberately-constructed breakwaters, sea walls, or jettys, or otherwise, they could have been constructed by
dredging, and these require maintenance by further periodic dredging. An example of the former kind is at Long
Beach Harbor, California, and an example of the latter kind is San Diego Harbor, California, which was, under
natural conditions, too shallow for modern merchant ships and warships.
In contrast, a natural harbor is surrounded on several sides by prominences of land. An example of this kind of
harbor is San Francisco Bay, California.
Harbors and ports are often confused with each other. A port is an artificial sea coast, lakeshore, or river shore
facility where ships, boats, and/or barges have loading and unloading procedures carried out, including those for
passengers or livestock. A port may consist of piers, docks, quays, wharves, jettys, and/or slipways, all of which can
have cargo cranes, grain elevators, ramps, and/or bulk-cargo handling machinery utilizing conveyor belts built upon
them. For example, very long conveyor belts are used for loading and unloading coal or ores to/from ships and
barges. Furthermore, ports may have equipment for loading or unloading petroleum or other liquid cargoes to/from
tankers.
Ports often have warehouses and other buildings for the storage and distribution of goods, or have magazine
buildings for naval ordinance and other explosives. There are also ground transportation systems that connect the
port with inland locations, such as railroad terminals, truck terminals, and/or pipeline terminals for carrying goods
and materials to and from the port.
Artificial harbors
Artificial harbors are frequently built for use as ports. The largest artificially created harbor is the Port of Rotterdam
in Rotterdam, Netherlands. Other large and busy artificial harbors are located in Houston, Texas, Long Beach,
California, and San Pedro, California.
Natural harbors
A natural harbor is a landform where a part of a body of water is
protected and deep enough to furnish anchorage. Many such harbors
are rias. Natural harbors have long been of great strategic naval and
economic importance, and many great cities of the world are located
on them. Having a protected harbor reduces or eliminates the need for
breakwaters as it will result in calmer waves inside the harbor.
A natural harbor in Vizhinjam, India
Harbor
59
Ice-free harbors
For harbors near the North and South Poles, being ice-free is an important advantage, especially when it is
year-round. Examples of these include Murmansk, Russia; Pechenga, Russia, formerly Petsamo, Finland);
Vladivostok, Russia; St. Petersburg, Russia; Hammerfest, Norway; Vardø, Norway; and Prince Rupert Harbour,
Canada. The world's southmost harbor, located at Antarctica's Winter Quarters Bay (77° 50′ South), is potentially
ice-free, depending on the summertime pack ice conditions.[1]
Tidal harbor
A tidal harbor is a type of harbor that can only be entered or exited at certain tidal levels.[2]
Important harbors
Although the world's busiest port is a hotly contested title, in 2006 the
world's busiest harbor by cargo tonnage was the Port of Shanghai.[3]
The following are large natural harbors:
• Baltimore's Inner Harbor, Maryland, United States
• Boston Harbor, Massachusetts, United States
• Bremerhaven, Germany
• Buenos Aires, Argentina
• Cartagena, Colombia
• Charleston, South Carolina, United States
• Cork Harbour, Ireland
• Duluth, Minnesota, United States
• Durban, South Africa
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Falmouth, Cornwall, England, United Kingdom
Visakhapatnam, Andhra Pradesh, India
Freetown Harbour, Sierra Leone
Golden Horn, Istanbul, Turkey
Izmir's Inner Harbor, Izmir, Turkey
Gothenburg, Sweden
Grand Harbour, Malta
Halifax Harbour, Nova Scotia, Canada
Hamburg Harbour, Germany
Hampton Roads, Norfolk, Virginia, United States
Karachi, Sindh, Pakistan
Kingston, Jamaica
Kobe Harbour, Kobe, Japan
Kochi, India
The tiny harbour at the village of Clovelly,
Devon, England
Harbor
60
• Lushunkou, Dalian, China
• Mahon, Minorca, Spain
• Manila Bay, Philippines
• Milford Haven, Wales, United Kingdom
• Montevideo, Uruguay
• Mumbai, India
• Nassau, Bahamas
• New York Harbor, United States
• Oslofjord, Norway
Old Harbour in Lüneburg, Germany.
• Pearl Harbor, Honolulu, Hawaii, United States
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Piraeus, Attica, Hellas, Greece
Plymouth Sound, Devon, England, United Kingdom
Poole Harbour, Dorset, England, United Kingdom
Port Jackson, Sydney, New South Wales, Australia
Port of Tyne, Tyne & Wear, United Kingdom
Port Phillip, Victoria, Australia
Rio de Janeiro, Guanabara Bay, Brazil
Rotterdam, Netherlands
Salvador, Brazil
San Diego Bay, San Diego, California, United States
San Francisco Bay, California, United States
Sankt Petersburg, Russia
Sevastopol Harbour, Sevastopol, Ukraine
Tanger-Med, Tangier, Morocco
Tauranga Harbour, Tauranga, New Zealand
Tokyo Bay, Tokyo, Japan
Trincomalee, Sri Lanka
Vancouver, Canada
Victoria Harbour, Hong Kong
Chennai port, India
Vizhinjam, India
Wellington Harbour, New Zealand
Willemstad, Curaçao, Netherlands Antilles
Other notable harbors include:
• Belém, Brazil
• Kahului, Hawaii, United States
• Kaipara Harbour, New Zealand, believed to be the worlds largest
natural harbour.
• Kaohsiung, Taiwan
• Keelung, Taiwan
• Kilindini Harbour, Kenya
• Keppel Harbour, Singapore
• Manukau Harbour, Auckland, New Zealand
• New Haven Harbor, Connecticut, United States
• Port of Antwerp, Flanders, Belgium
• Port of Bruges-Zeebrugge, Flanders, Belgium
Capri harbour, Italy seen from Anacapri
Harbor
•
•
•
•
•
•
61
Port of Genoa, Italy
Portland Harbour, Dorset, England, United Kingdom
Rades, Tunisia
Trondheim, Norway
Port of Gdańsk, Poland
Port of Szczecin, Poland
See also
•
•
•
•
•
•
•
•
•
•
•
Boyd's Automatic tide signalling apparatus
Dock
Dockyard
Ice pier
Marina, List of Marinas
Port
Roadstead
Quay
Seaport, List of seaports
Wharf
Inland harbor
Notes
[1] U.S. Polar Programs (http:/ / www. nsf. gov/ about/ budget/ fy2000/ 00OPP. htm) National Science Foundation FY2000.
[2] Port Cities - tide harbour (http:/ / portcities. hartlepool. gov. uk/ server. php?show=ConGlossary. 105)
[3] AAPA World Port Rankings 2006 (http:/ / aapa. files. cms-plus. com/ Statistics/ worldportrankings_2006. xls)
Port
62
Port
A port is a location on a coast or shore containing one
or more harbors where ships can dock and transfer
people or cargo to or from land. Port locations are
selected to optimize access to land and navigable water,
for commercial demand, and for shelter from wind and
waves. Ports with deeper water are rarer, but can handle
larger, more economical ships. Since ports throughout
history handled every kind of traffic, support and
storage facilities vary widely, may extend for miles,
and dominate the local economy. Some ports have an
important, perhaps exclusively military role.
Seaport, a 17th Century depiction by Claude Lorrain, 1638
Distribution
Ports often have cargo-handling equipment, such as
cranes (operated by longshoremen) and forklifts for use
in loading ships, which may be provided by private
interests or public bodies. Often, canneries or other
processing facilities will be located nearby. Some ports
feature canals, which allow ships further movement
inland. Access to intermodal transportation, such as
trains and trucks, are critical to a port, so that
passengers and cargo can also move further inland
beyond the port area. Ports with international traffic
have customs facilities. Harbour pilots and tugboats
may maneuver large ships in tight quarters when near
docks.
The Port of Dover, UK.
Port types
The terms "port" and "seaport" are used for different
types of port facilities that handle ocean-going vessels,
and river port is used for river traffic, such as barges
and other shallow-draft vessels. Some ports on a lake,
river, or canal have access to a sea or ocean, and are
sometimes called "inland ports".
A fishing port is a port or harbor facility for landing
and distributing fish. It may be a recreational facility,
but it is usually commercial. A fishing port is the only
port that depends on an ocean product, and depletion of
fish may cause a fishing port to be uneconomical. In
recent decades, regulations to save fishing stock may
limit the use of a fishing port, perhaps effectively closing it.
The Port of Hamburg, Germany.
Port
63
A "dry port" is a term sometimes used to describe a
yard used to place containers or conventional bulk
cargo, usually connected to a seaport by rail or road.
A warm water port is where the water does not freeze
in winter time. Because they are available year-round,
warm water ports can be of great geopolitical or
economic interest.
A seaport is further categorized as a "cruise port" or a
"cargo port". Additionally, "cruise ports" are also
known as a "home port" or a "port of call". The "cargo
port" is also further categorized into a "bulk" or "break
bulk port" or as a "container port".
A cruise home port is the port where cruise-ship
passengers board (or embark) to start their cruise and
also debark (or disembark) the cruise ship at the end of
their cruise. It is also where the cruise ship's supplies
are loaded for the cruise, which includes everything
from fresh water and fuel to fruits, vegetable,
champagne, and any other supplies needed for the
cruise. "Cruise home ports" are a very busy place
during the day the cruise ship is in port, because
off-going passengers debark their baggage and
on-coming passengers board the ship in addition to all
the supplies being loaded. Currently, the Cruise Capital
of the World is the Port of Miami, Florida, closely
followed behind by Port Everglades, Florida and the
Port of San Juan, Puerto Rico.
The port of Piraeus in Greece
Visakhapatnam Port, Andhra Pradesh, India.
A port of call is an intermediate stop for a ship on its
sailing itinerary, which may include up to half a dozen
ports. At these ports, a cargo ship may take on supplies
or fuel, as well as unloading and loading cargo. But for
a cruise ship, it is their premier stop where the cruise
lines take on passengers to enjoy their vacation.
Port of Kobe, Japan at twilight
Port
64
Port of Miami
Port Newark, seen across Newark Bay
Cargo ports, on the other hand, are quite different from cruise ports,
because each handles very different cargo, which has to be loaded and
unloaded by very different mechanical means. The port may handle
one particular type of cargo or it may handle numerous cargoes, such
as grains, liquid fuels, liquid chemicals, wood, automobiles, etc. Such
ports are known as the "bulk" or "break bulk ports". Those ports that
handle containerized cargo are known as container ports. Most cargo
ports handle all sorts of cargo, but some ports are very specific as to
what cargo they handle. Additionally, the individual cargo ports are
divided into different operating terminals which handle the different
cargoes, and are operated by different companies, also known as
terminal operators or stevedores.
Cargo port in Hilo, Hawaii
Port
65
Access
Ports sometimes fall out of use. Rye, East Sussex was an important English port in the Middle Ages, but the
coastline changed and it is now 2 miles (3.2 km) from the sea, while the ports of Ravenspurn and Dunwich have
been lost to coastal erosion. Also in the United Kingdom, London, the River Thames was once an important
international port, but changes in shipping methods, such as the use of containers and larger ships, put it at a
disadvantage.
Ports of the World
Africa
• Ports and harbours in South Africa
Asia
For details on East Asian ports, see the List of East Asian ports.
North America
The ports of the United States handle more than 2 billion metric tons of domestic and import/export cargo annually.
American ports are responsible for moving over 99 percent of the country's overseas cargo.
For details on U.S. Ports, see the List of ports in the United States. For details on all North American ports, see the
List of North American ports.
See also
• Megaproject
• Megaprojects and risk
Water port topics
•
•
•
•
•
•
Bandar (Persian word for "port" or "haven")
Dock (maritime)
Harbour
Marina - port for recreational boating
Port operator
Ship transport
Other types of ports
• Airport
• Spaceport
• Port of entry
Lists
•
•
•
•
•
List of seaports
World's busiest port
List of world's busiest transshipment ports
List of world's busiest port regions
List of busiest container ports
Port
66
•
•
•
•
•
List of North American ports
List of ports in the United States
List of East Asian ports
Sea rescue organisations
Computer port
External links
•
•
•
•
Port Industry Statistics, American Association of Port Authorities [1]
Information on yachting facilities at 1,613 ports in 191 countries from Noonsite.com [2]
Social & Economic Benefits of PORTS [3] from "NOAA Socioeconomics" website initiative
World sea ports search [4]
References
[1]
[2]
[3]
[4]
http:/ / www. aapa-ports. org/ Industry/ content. cfm?ItemNumber=900& navItemNumber=551
http:/ / www. noonsite. com/ text/ Countries
http:/ / www. ncdc. noaa. gov/ oa/ esb/ ?goal=commerce& file=obs/ marine/ ports/
http:/ / www. etoolsage. com/ Query/ PortSearching. asp?toolsort=1100
67
Coastal Management
Integrated coastal zone management
Integrated coastal zone management (ICZM) or Integrated coastal management (ICM) is a process for the
management of the coast using an integrated approach, regarding all aspects of the coastal zone, including
geographical and political boundaries, in an attempt to achieve sustainability.
This concept was born in 1992 during the Earth Summit of Rio de Janeiro. The policy regarding ICZM is set out in
the proceedings of the summit within Agenda 21, Chapter 17.
The European Commission defines the ICZM as follows:ICZM is a dynamic, multidisciplinary and iterative process to promote sustainable management of
coastal zones. It covers the full cycle of information collection, planning (in its broadest sense), decision
making, management and monitoring of implementation. ICZM uses the informed participation and
cooperation of all stakeholders to assess the societal goals in a given coastal area, and to take actions
towards meeting these objectives. ICZM seeks, over the long-term, to balance environmental, economic,
social, cultural and recreational objectives, all within the limits set by natural dynamics. 'Integrated' in
ICZM refers to the integration of objectives and also to the integration of the many instruments needed
to meet these objectives. It means integration of all relevant policy areas, sectors, and levels of
administration. It means integration of the terrestrial and marine components of the target territory, in
both time and space.
To further understand the idea of ICZM several aspects can be defined and further explained. The coastal zone, the
concept of sustainability and the term integration all within a coastal management context can be individually
defined, while the expectations and framework of ICZM can be further explained. This entry uses the example of the
New Zealand national framework to illustrate ICZM.
Defining the Coastal Zone
Defining the Coastal zone is of particular importance to the idea of ICZM. But the fuzziness of borders due to the
dynamic nature of the coast makes it difficult to clearly define. Most simply the coast can be thought of as an area of
interaction between the land and the ocean. Ketchum (1972)[1] defined the area as:
The band of dry land and adjacent ocean space (water and submerged land) in which terrestrial
processes and land uses directly affect oceanic processes and uses, and vice versa.
Issues arise with the diversity of features present on the coast and the spatial scales of the interacting systems. Coasts
being dynamic in nature are influenced differently all around the world. Influences such as river systems, may reach
far inland increasing the complexity and scale of the zone. These issues make it difficult to clearly identify
hinterlands and subscribe any subsequent management.
Whilst acknowledging a physical coastal zone, the inclusion of ecosystems, resources and human activity within the
zone is important. It is the human activities that warrant management. These activities are responsible for disrupting
the natural coastal systems. To add to the complexity of this zone, administrative boundaries use arbitrary lines that
dissect the zone, often leading to fragmented management. This sectored approach focuses on specific activities such
as land use and fisheries, often leading to adverse effects in another sector.
Integrated coastal zone management
The importance of the Coastal Zone and the need for management
The dynamic processes that occur within the coastal zones produce diverse and productive ecosystems which have
been of great importance historically for human populations[2] . Coastal margins equate to only 8% of the worlds
surface area but provide 25% of global productivity. Stress on this environment comes with approximately 70% of
the world’s population being within a day’s walk of the coast[3] . Two-thirds of the world’s cities occur on the coast[4]
.
Valuable resources such as fish and minerals are considered to be common property and are in high demand for
coastal dwellers for subsistence use, recreation and economic development[5] . Through the perception of common
property, these resources have been subjected to intensive and specific exploitation. For example; 90% of the world’s
fish harvest comes from within national exclusive economic zones, most of which are within the sight of shore[3] .
This type of practice has led to a problem that has cumulative effects. The addition of other activities adds to the
strain placed on this environment. As a whole, human activity in the coastal zone generally degrades the systems by
taking unsustainable quantities of resources. The effects are further exacerbated with the input of pollutant wastes.
This provides the need for management. Due to the complex nature of human activity in this zone a holistic approach
is required to obtain a sustainable outcome.
The concept of sustainability
The concept behind the idea of ICZM is sustainability. For ICZM to succeed, it must be sustainable. Sustainability
entails a continuous process of decision making, so there is never an end-state just a readjustment of the equilibrium
between development and the protection of the environment[6] . The concept of Sustainability or sustainable
development came to fruition in the 1987 report of the World Commission on Environment and Development, Our
Common Future. It stated sustainable development is “to meet the needs of the present without compromising the
ability of future generations to meet their own needs”[7] .
Highlighted are three main standpoints which summarise the idea of Sustainable development, they are:
• Economic development to improve the quality of life of people
• Environmentally appropriate development
• Equitable development[6]
To simplify these points, sustainability should acknowledge the right of humans to live a life that is healthy and
productive. It should allow for equal distribution of benefits to all people and in doing so protect the environment
through appropriate use[6] .
Sustainability is by no means a set of prescriptive actions, more accurately it is a way of thinking. Adapting this way
of thinking paves the way for a longer-term view with a more holistic approach, something successful ICZM can
achieve[8] .
Expectations of ICZM
As previously stated, for ICZM to be successful it must adhere to the principles that define sustainability and act
upon them in ways that are integrated. An optimal balance between environmental protection and the development of
economic and social sectors is paramount[9] . As part of the holistic approach ICZM applies, many aspects within a
coastal zone are expected to be considered and accounted for. These include but are not limited to: the spatial,
functional, legal, policy, knowledge, and participation dimensions[10] . Below are four identified goals of ICZM:
•
•
•
•
Maintaining the functional integrity of the coastal resource systems;
Reducing resource-use conflicts;
Maintaining the health of the environment;
Facilitating the progress of multisectoral development[11]
68
Integrated coastal zone management
Failure to include these aspects and goals would lead to a form of unsustainable management, undermining the
paradigms explicit to ICZM.
Defining Integration
The term ‘integration’ can be adopted for many different purposes, it is therefore quite important to define the term in
the context of the management of the coastal zone to appreciate the intentions of ICZM. Integration within ICZM
occurs in and between many different levels, 5 types of integration that occur within ICZM[6] , are explained below;
Integration among sectors: Within the coastal environment there are many sectors that operate. These human
activities are largely economic activities such as tourism, fisheries, and port companies. A sense of co-operation
between sectors is the main requirement for sector integration within ICZM. This comes from the realisation of a
common goal focused around sustainability and the appreciation of one another within the area.
Integration between land and water elements of the coastal zone: This is the realisation of the physical
environment being a whole. The coastal environment is a dynamic relationship between many processes all of which
are interdependent. The link must be made between imposing a change on one system or feature and its inevitable
‘flow on’ effects.
Integration among levels of government: Between levels of governance, consistency and co-operation is needed
throughout planning and policy making. ICZM is most effective where initiatives have common purpose at local,
regional, and national levels. Common goals and actions increase efficiency and mitigate confusion.
Integration between nations: This sees ICZM as an important tool on a global scale. If goals and beliefs are
common on a supranational scale, large scale problems could be mitigated or avoided.
Integration among disciplines: Throughout ICZM, knowledge should be accepted from all disciplines. All means of
scientific, cultural, traditional, political and local expertise need to be accounted for. By including all these elements
a truly holistic approach towards management can be achieved.
The term integration in a coastal management context has many horizontal and vertical aspects, which reflects the
complexity of the task and it proves a challenge to implement.
ICZM Framework
Management must embrace a holistic viewpoint of the functions that makeup the complex and dynamic nature of
interactions in the coastal environment[12] . Management framework must be applied to a defined geographical limit
(often complicated) and should operate with a high level of integration[11] . Due to the diverse nature of the world’s
coastline and coastal environments, it is not possible to create a framework that is ‘one-size-fits-all.’ Different
activities, interests and issues also complicate matters. So management will always be unique to countries, regions
and ultimately on a local scale.
A common thought process and decision making framework however, can be fairly uniform as a part of ICZM
around the world. To achieve the principles set out in sustainable types of management a step by step process can be
adhered to.
Firstly, issues and problems need to be identified and assessments of these need to be quantified. This first step will
include integration between government, sectoral entities and local residents. The assessments also have to be broad
in their application. Once the issues and problems have been identified and weighted, an effective management plan
can be made. The plan will be specific to the area in question. Thirdly, the adoption of the plan can be carried out.
They can be legally binding statutory plans, strategies or objectives which are generally quite powerful or they can
be non-statutory processes and can act as a guide for future development[8] . This duality is largely beneficial as the
future can be taken into account, but still provide for a firm stance based in the present[2] . The fourth step is
implementation, this active phase includes; law enforcement, education, development etc. The implementation
activities will be of course, be as unique as their environments and can take many forms. The last phase is evaluation
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Integrated coastal zone management
of the whole process. The principles of sustainability mean that there is no ‘end state.’ ICZM is an ongoing process
which should constantly readjust the equilibrium between economic development and the protection of the
environment. Feedback is a crucial part of the process and allows for continued effectiveness even when a situation
may change.
Constraints of ICZM
Major constraints of ICZM are mostly institutional, rather than technological[10] . The ‘top-down’ approach of
administrative decision making sees problematisation as a tool promoting ICZM through the idea of sustainability[10]
. Community-based ‘bottom-up’ approaches can perceive problems and issues that are specific to a local area. The
benefit of this is that the problems are real and acknowledged rather than searched for to fit an imposed strategy or
policy. Public consultation and involvement is very important for current ‘top-down’ approaches, as it can
incorporate this ‘bottom-up’ idea into the policies made. Prescriptive ‘top-down’ methods have not able to effectively
address problems of resource utilization in poor coastal communities as perceptions of the coastal zone differ with
regard to developed and developing countries[10] . This leads on to another constraint to ICZM, the idea of common
property.
The coastal environment has huge historical and cultural connections with human activity. Its wealth of resources
have provided for millennia, with regard to ICZM how does management become legally binding if the dominant
perception of the coast is of a common area available to all? And should it?[3] Enforcing restrictions or change to
activities within the coastal zone can be difficult as these resources are often very important to people’s livelihoods.
The idea of the coast being common property fouls ‘top-down’ approaches. The idea of common property itself is not
all that clean, This perception can lead to cumulative exploitation of resources – the very problem this management
seeks to extinguish.
ICZM: The New Zealand case study
New Zealand is quite unique as it uses sustainable management within legislation, with a high level of importance
placed on to the coastal environment[2] . The Resource Management Act (RMA) (1991) promoted sustainable
development and it mandated the preparation of a New Zealand Coastal Policy Statement (NZCPS), a national
framework for coastal planning. It is the only national policy statement that was mandatory[13] . All subsequent
planning must not be inconsistent with the NZCPS making it a very important document[2] . Regional authorities are
required to produce Regional coastal policy plans under the RMA (1991) but strangely enough, they only need to
include the marine environment seaward of the mean high water mark. But many regional councils have chosen to
integrate the ‘dry’ landward area within their plans, breaking down the artificial barriers[2] . This attempt at ICZM is
still in its early days running into many legislative hurdles and is yet to achieve a fully ecosystems-based approach.
But as part of ICZM, evaluation and adoption of changes is important and ongoing changes to the NZCPS in the
form of reviews is currently happening[13] . This will provide an excellent stepping stone for future initiatives and the
development of a fully integrated form of coastal management.
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Integrated coastal zone management
Conclusion
The Integrated Coastal Zone Management (ICZM) appears to be a key element for the sustainable development of
these zones. However this recent notion may not be adapted to all cases[14] . Successful implementation is still a
major challenge to the idea of ICZM.
See also
• Coastal management
References
[1] KETCHUM, B. H. 1972. The water's edge: critical problems of the coastal zone. In: Coastal Zone Workshop, 22 May-3 June 1972 Woods
Hole, Massachusetts. Cambridge: MIT Press.
[2] KAY, R. & ALDER, J. 1999. Coastal Planning and Management, London, E & FN Spon.
[3] BROWN, K., TOMPKINS, E. L. & ADGER, N. 2002. Making Waves: Integrating coastal conservation and development, London, Earthscan
Publications Limited.
[4] CROOKS, S. & TURNER, R. K. 1999. Integrated coastal management: sustaining estuarine natural resources. Advances in Ecological
Research, 29, 241-289.
[5] BERKES, F. 1989. Common property resources: Ecology and community-based sustainable development, London.
[6] CICIN-SAIN, B. 1993. Sustainable Development and Integrated Coastal Management. Ocean and Coastal Management, 21, 11-43.
[7] WORLD, COMMISSION, ON, ENVIRONMENT, AND & DEVELOPMENT 1987. Towards Sustainable future, "Our common future".
New York: Oxford University Press.
[8] MASSELINK, G. & HUGHES, M. 2003. Introduction to Coastal Processes and Geomorphology, London, Hodder Arnold.
[9] CICIN-SAIN, B. & KNECHT, R. 1998. Integrated coastal and ocean management: concepts and practices. Washington D.C.: Island Press.
[10] IDRUS, M. R. 2009. Hard Habits to Break: Investigating Coastal Resource Utilisations and Management Systems in Sulawesi, Indonesia
Doctor of Philosophy in Environmental Science, University of Canterbury.
[11] THIA-ENG, C. 1993. Essential Elements of Integrated Coastal Zone Management. Ocean and Coastal Management, 21, 81-108.
[12] WILLIAMS, A. & MICALLEF, A. 2009. Beach Management: Principles and Practice, London, Earthscan Publications Limited.
[13] PEART, R. 2007. Beyond the Tide: Inetgrating the management of New Zealand's coasts, Auckland, Environmental Defence Society Inc.
[14] Billé, R. (2008) “Integrated Coastal Zone Management: four entrenched illusions”. S.A.P.I.EN.S. 1 (2) (http:/ / sapiens. revues. org/
index198. html)
External links
• European Commission Coastal Zone Policy (http://ec.europa.eu/environment/iczm/home.htm)
• ENCORA Coastal WIKI -EU Coordination Action on ICZM (http://www.encora.eu/coastalwiki/Main_Page)
• Examining Best Practices in Coastal Zone Planning (http://www.sfu.ca/cstudies/science/alertbay.htm)
Lessons and Applications for British Columbia's Central Coast
• Coastal Zone Management Policy and Politics Class (http://www.public.iastate.edu/~sws/cp/coastalpolicy.
html)
• Safecoast (http://www.safecoast.org) Knowledge exchange on coastal flooding and climate change in the North
Sea region
• ICZM principles (http://www.tvlink.org/vnr.cfm?vidID=53)
• ZonaCostera (http://www.zonacostera.info/index.php?title=Portada) | KüstenZone | CoastalZone (http://
coastalzone.info/index.php?title=Main_Page) | FrangeCôtière | KustStrook: Wiki in development with relevant
and on-time information, useful for the integrated management of the coastal zones of our world. Integrated
development is everybody's business!
• EUCC Marine Team: ICZM in Europe (http://marine-team.eucc-d.de)
• Coastal Zone Management Unit in Barbados (http://www.coastal.gov.bb)
Videos
• Free Educational Videos about Coastal Policy and Zone Management (http://www.public.iastate.edu/~sws/
cp/coastalpolicyvideos.html)
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