Shoreline Processes
Sediment Transport
Do you really want to buy that
beachfront house?
 Describe the processes that generate coasts
 Beach anatomy
 Seasonal changes
 Longshore transport
 How do the structures we build change the shoreline
This week we will study the
types of coasts and
beaches and the natural
processes that create and
maintain them
Here today, gone tomorrow: sediment
transport and beach evolution
The shore takes on
many forms along the
WA coast and Puget
Sound
Weather, waves and
gravity continue to
shape the shorelines
Beaches are dynamic
Major Zones
Coastal areas are regions of
change in which the sea acts
to alter the shape and the
configuration of the land
 Coastal area: land edge that borders the sea
 Width varies
 geography
 climate
 vegetation
 Shore: outer limit of wave action on the bottom to the limit
of the waves’ direct influence on land
 Beach: accumulation of sand or gravel that occupies part
of the shore
Anatomy of a beach
 Berm: ledge or terrace with flat tops
 formed by wave-deposited material
 Beach face: seaward slope, dependent on sediment type and
wave energy
 Troughs and bars run parallel to beach
 Change seasonally
Fig. 12.6
Seasonal Beach Changes
Summer Profile
Winter Profile
How do waves move sediments?
 Wind = waves
 Breaking wave = turbulence
 Swash moves sediment onshore diagonally
 Backwash moves sediment straight down beach
 Swash + backwash = zigzag
 http://www.youtube.com/watch?v=tN42EWWTP3w&feature=
related
Fig. 12.20
Materials on the move
A constant river of sand
and gravel flows along
beaches.
Shore drift or longshore
drift can move materials
from eroding bluffs and
streams to shorelines miles
away.
Weather and waves pick
up particles in one area
and drop them off in
another area.
Sources & Sinks
 Sources along the WA coast and Puget Sound include eroding
bluffs, rivers, and streams
 Sinks appear as spits, bars, tombolos, beaches (…can also be a
source if supply is blocked or changes….)
Sink or Source?
Source:
Sink:
Direction of drift or longshore transport:
spit
bluff
Human intervention in natural beach
evolution
Wave action and
longshore transport can
erode beaches and be a
hazard to boat harbors
 Build structures to stop beach
erosion and stabilize beaches
 jetties, groins, seawalls
 Build structures to protect
harbors
 Breakwaters
 Building dams
Beaches: River of Sand
The end