2.1
DSE-Geography
Water
Summary ~Section 2
2.1 How does water shape our rivers & coasts?
Name:
(
)
Date:
Class:
4
1.
What is the water cycle?

It is the continuous movement of water between the ___________, the ______and the _____

Water on the Earth’s surface is returned to the atmosphere through the process
of ________________. The water vapour will later ________________into liquid or
solids that fall to the ground again. This ________ process is known as the water
cycle.
Figure 1
A.
When the droplets in the cloud become too heavy to support, they fall.
B.
Precipitation falls on the vegetation and trapped by it.
C.
It flows down the slope in sheets.
D.
After reaching the ground, water seeps into the soil.
E.
Water vapour released from both the earth’s surface (evaporation) and
vegetation
1
2.1
DSE-Geography
Water
The operation of water cycle
Water has three physical states: solid (ice), liquid (water) and gas (watpour).
Input:
1 Precipitation
When air is saturated with water vapor, water vapor condenses to form __________.
When water droplets become larger and are too heavy to remain suspended in the air,
they fall to the ground as precipitation.
Transfer:
1.
2.

3.
4.
5.

6.

7.

8.
9.





Precipitation falls on vegetation and is caught there.
Some water reaches the ground by dripping off leaves
(throughfall) or flowing down the trunk (stem flow).
Some water seeps into the soil, forming soil storage.
Some water stored in soil flows along the slope as throughflow.
Some soil water flows downward as percolation until it reaches
the water table.
Some ground water remains deep in the ground, while some
flows to the surface and into rivers or oceans.
Water flows on the surface as surface runoff. It includes
channel flow and overland flow.
Surface runoff following river channels is called channel flow.
The remaining surface runoff, flowing on the ground surface.
Outputs:
1.

2.

Water in soil, on the ground or in rivers and sea will absorb
heat energy from the sun. It will change into water vapour and
return to the atmosphere through the process of evaporation.
Water in vegetation is released into the atmosphere through
transpiration.
2
2.1
DSE-Geography
Water
2.
How does water shape our rivers and coasts?

The work of water creates a variety of _____________ and _____________
environments. Both ___________ and _________ factors that shape the Earth’s surface.
From source to mouth, a river develops distinct landform features. Most rivers consist of

______________ courses.
Coasts have various landform features formed by the wearing away of rocks or

transporting sediments by the waves to a new location. In Hong Kong, there are more
than 260 ______________ islands with magnificent coastlines and coastal features.
3.
What is a drainage/river basin?

It is a ______________ area of a river and its tributaries. It is also known as the river
______________ area.

The main stream and its ___________ form a drainage network or drainage system.

Adjacent river basins are separated by a ______________.
Figure 2

Name the various features in a drainage basin.
A
E
B
F
C
G
D

Mark on Figure 2 the first order stream with ‘1’, the second order stream with ‘2’ and so on.

What is the order of the drainage basin?
3
2.1
DSE-Geography

Water
Suppose the actual length of the channels in the drainage basin is 4.6 km and the total
area of the drainage basin is 1.07 km2. Calculate the drainage density of the drainage
basin. ________________________________________
Stream ordering
1.
2.
Stream ordering counted in the following ways:
all the smallest tributaries originating from their own sources are the 1 st order
streams
a stream of higher order is formed when two streams of the same order meet
Exercise
Stream Order
No. of Stream
Bifurcation Ratio
1
23
2
9
23/9
1 : 2.56
3
2
1 : 4.5
4
1
1:2
B.R. ~  tributaries,  stream storage, stability of the hydrological
cycle.  chance of flooding. (TRF) (TD vice versa)
TRF: >1:30 / TD 1:3
I.
Drainage density (km/km2)
Drainage
density
=
 It is the average length of channel per unit area of the drainage basin.
 In upland areas with impermeable rocks, high rainfall and steep slopes,
drainage density is high.
 So, when slopes are gentle, low rainfall and with permeable bedrock, the
drainage density is low. (they may have more ground water storage)
4
2.1
DSE-Geography

Water
Drainage pattern are governed by the _________ and _________structure of the
rock.
Drainage
________-________pattern
develops in areas with __________ rock structure
streams join one another at ________ angles
e.g. Kam Tin River
Drainage
develops in areas of alternate layers of ________ and
________ rocks
soft rocks eroded first to form __________ for the
tributaries
the tributaries join the main stream roughly at ______
angles
Drainage
develops in areas with lines of __________
intersecting at __________ angles
e.g. Tai Lam Chung area
Drainage
rivers flow downslope in different ____________ from
the top of a hill, e.g. __________ hills, volcanoes
e.g. Tai Mo Shan
Drainage
rivers flow from different directions towards the
__________ of a basin, e.g. lakes, which are
commonly found in inland basins
5
2.1
DSE-Geography
4.
Water
How does seawater shape our coasts?

A coast is the __________ of the land where it meets the sea.

__________ and __________ are the two agents shaping the coastal landforms.
Figure 3

The coastal zone
In which zone(s) do we find a beach?
A beach is found in

The coast contributes to the development of an area because it serves the functions
of __________ , __________ , ______________ and __________ trading.
The coast can be generally divided into several parts:
1.
Shore
- the area between the ___________and the low water level.
- It includes two parts ___________and ___________.
2.
Nearshore - the area between the low water level and the ___________
(lowest water level).
3.
Offshore
- extends seawards from the ___________water level.

A coast is a ___________.

Inputs: energy from wind, sediments from the sea

Outputs: sediments deposited on shores, energy dissipated by waves.
Sometimes beautiful coastal features can be regarded as another output.

The coast contributes to the ______________________of an area because it
serves the functions of defense, fishing, recreation and overseas trading.

In Hong Kong, much of our urban land has been modified and
______________________ from coastal areas. As a result, many parts of the
coastline have been ______________________.
6
2.1
DSE-Geography
Water
Summary ~Section 2
2.1 How does water shape our rivers & coasts?
Name:
(
)
Date:
Class:
4
5.
What is the water cycle?

It is the continuous movement of water between the atmosphere, the ocean and the land.

Water on the Earth’s surface is returned to the atmosphere through the process
of evaporation. The water vapour will later condense into liquid or solids that fall
to the ground again. This circular process is known as the water cycle.
Figure 1
A. Precipitation
When the droplets in the cloud become too heavy to support,
they fall.
B. intereception
Precipitation falls on the vegetation and trapped by it.
C. overland-flow
It flows down the slope in sheets.
D. Infiltration
After reaching the ground, water seeps into the soil.
E. Evapotranspiration Water
vapour released from
(evaporation) and vegetation
7
both
the earth’s
surface
2.1
DSE-Geography
Water
The operation of water cycle
Water has three physical states: solid (ice), liquid (water) and gas (water vapour).
Input:
1 Precipitation
When air is saturated with water vapour, water vapour condenses to form droplets.
When water droplets become larger and are too heavy to remain suspended in the air,
they fall to the ground as precipitation.
Transfer:
1. Interception
2. Throughfall
& stem flow

3. Infiltration
4. Throughflow
5. Percolation

6. Ground
water flow

7. Surface
runoff

8. Channel
flow
9. Overland
flow

Precipitation falls on vegetation and is caught there.
Some water reaches the ground by dripping off leaves
(throughfall) or flowing down the trunk (stem flow).
Some water seeps into the soil, forming soil storage.
Some water stored in soil flows along the slope as throughflow.
Some soil water flows downward as percolation until it reaches
the water table.
Some ground water remains deep in the ground, while some
flows to the surface and into rivers or oceans.
Water flows on the surface as surface runoff. It includes
channel flow and overland flow.
Surface runoff following river channels is called channel flow.

The remaining surface runoff, flowing on the ground surface.



Outputs:
1. Evaporation

2. Transpiration

Water in soil, on the ground or in rivers and sea will absorb
heat energy from the sun. It will change into water vapour and
return to the atmosphere through the process of evaporation.
Water in vegetation is released into the atmosphere through
transpiration.
8
2.1
DSE-Geography
Water
F.
How does water shape our rivers and coasts?

The work of water creates a variety of fluvial and coastal environments. Both physical
and human factors that shape the Earth’s surface.
From source to mouth, a river develops distinct landform features. Most rivers consist of

three courses.
Coasts have various landform features formed by the wearing away of rocks or

transporting sediments by the waves to a new location. In Hong Kong, there are more
than 260 outlying islands with magnificent coastlines and coastal features.
G.
What is a drainage/river basin?

It is a drainage area of a river and its tributaries. It is also known as the river
catchment area.

The main stream and its tributaries form a drainage network or drainage system.

Adjacent river basins are separated by a watershed.
Figure 2

Name the various features in a drainage basin.
A Source of river
E Confluence points
B Watershed
F Distributary
C Main river
G Mouth of the river
D Tributary

Mark on Figure 2 the first order stream with ‘1’, the second order stream with ‘2’ and so on.

What is the order of the drainage basin?
It is a third order basin.
9
2.1
DSE-Geography

Water
Suppose the actual length of the channels in the drainage basin is 4.6 km and the total
area of the drainage basin is 1.07 km2. Calculate the drainage density of the drainage
basin. 4.6 km ÷ 1.07 km2 = 4.3 km/km2
Stream ordering
3.
4.
Stream ordering counted in the following ways:
all the smallest tributaries originating from their own sources are the 1st
order streams
a stream of higher order is formed when two streams of the same order
meet
Exercise
Stream Order
No. of Stream
Bifurcation Ratio
1
23
2
9
23/9
1 : 2.56
3
2
1 : 4.5
4
1
1:2
B.R. ~  tributaries,  stream storage, stability of the hydrological
cycle.  chance of flooding. (TRF) (TD vice versa)
TRF: >1:30 / TD 1:3
II.
Drainage density (km/km2)
Drainage
density
=
Total length of the
channel
Total area of the basin
 It is the average length of channel per unit area of the drainage basin.
 In upland areas with impermeable rocks, high rainfall and steep slopes,
drainage density is high.
 So, when slopes are gentle, low rainfall and with permeable bedrock, the
drainage density is low. (they may have more ground water storage)
10
2.1
DSE-Geography

Water
Drainage pattern are governed by the gradient and geological structure of the rock.
Dendritic Drainage
Branch-like pattern
develops in areas with uniform rock structure
streams join one another at acute angles
e.g. Kam Tin River
Trellis Drainage
develops in areas of alternate layers of hard and
soft rocks
soft rocks eroded first to form valleys for the
tributaries
the tributaries join the main stream roughly at right
angles
Rectangular Drainage
develops in areas with lines of weakness
intersecting at right angles
e.g. Tai Lam Chung area
Radial Drainage
rivers flow downslope in different directions from the
top of a hill, e.g. conical hills, volcanoes
e.g. Tai Mo Shan
Centripetal Drainage
rivers flow from different directions towards the
centre of a basin, e.g. lakes, which are commonly
found in inland basins
11
2.1
DSE-Geography
H.
Water
How does seawater shape our coasts?
I. A coast is the edge of the land where it meets the sea.
J. Waves and tides are the two agents shaping the coastal landforms.
K. Label Figure 3 to show the coastal zone.
Figure 3
The coastal zone
L. In which zone(s) do we find a beach?
A beach is found in the shore/the foreshore and the backshore.
M. The coast contributes to the development of an area because it serves the functions
of defense, fishing, recreation and overseas trading.
The coast can be generally divided into several parts:
1.
Shore
- the area between the coastline and the low water level.
- It includes two parts backshore and foreshore.
2.
Nearshore - the area between the low water level and the shoreline (lowest
water level).
3.
Offshore
- extends seawards from the lowest water level.

A coast is a system.

Inputs: energy from wind, sediments from the sea

Outputs: sediments deposited on shores, energy dissipated by waves.
Sometimes beautiful coastal features can be regarded as another output.

The coast contributes to the development of an area because it serves the
functions of defense, fishing, recreation and overseas trading.

In Hong Kong, much of our urban land has been modified and reclaimed from
coastal areas. As a result, many parts of the coastline have been straightened.
12