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River, Floods and Management
The Drainage Basin Hydrological Cycle: The Water Balance




















The Process:
1. Precipitation falls towards the ground
2. The precipitation is intercepted and will land on plants and not reach the ground at all. They eventually reach
the ground through throughfall and stemflow
3. Some of the…

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River, Floods and Management
Flow Groundwater The groundwater, beneath the Earth's surface, flows at a slow rate through
flow sedimentary rock and is seeped in
Flow Baseflow The water that keeps rivers flowing even during a drought
The Storm Hydrograph





















Urban vs Forested Storm Hydrograph:
















Smooth vs Rough Storm Hydrograph:








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River, Floods and Management




Factors Affecting the Storm Hydrograph
Influence Description/Explanation
Precipitatio Intensity and Duration High intensity and long duration of storm = infiltration
n of Storm capacity of the soil is exceeded = easily runs off surface =
steep rising limb and higher discharge

Antecedent Rainfall Heavy rain falling…

Page 4

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River, Floods and Management
















The Long Profile Changing Processes
Erosion:
Rivers erode because they possess energy . The total energy depends on:
the weight of the water the greater the mass of water the more energy it will possess due to the force of
gravity on it
the height of…

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River, Floods and Management
Traction Large stones and boulders are rolled along the river bed. Usually at high discharge
and high energy levels
Saltation Small stones are lifted up by the current and are bounced along the river bed . Usually
at high energy levels
Suspension Small particles (sand and…

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River, Floods and Management












Small Particles Large Particles
Transportatio Low velocity lighter particles are easier to High velocity heavier particles are more
n carry difficult to carry
Erosion High velocity clay and silt tend to stick High velocity large particles are harder to
together eroded
Deposition Low velocity some may…

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River, Floods and Management



Upper Course Middle Course Lower Course
Landforms Small waterfalls Rapids Larger meanders
Rapids Small meanders Levees
Potholes Small floodplains Floodplains
Large boulders
Uneven steep river bed
Size of Material Larger particles Medium sized particles Smaller particles
Erosion Vertical Erosion Hydraulic Lateral Erosion Hydraulic Reduced erosion, some…

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River, Floods and Management
and banks so there will be less friction. Lowest velocity where the water is touching the bed
and banks because there will be more friction there

Wetted The wetted perimeter is all the surface of the bed and banks that the water touches
Perimeter Upper Course…

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River, Floods and Management




Waterfalls and Rapids:
A waterfall is a sudden fall of water that occurs where there are rapid changes in gradient in the river's course
caused by changes in geology , plateaus and rejuvenation giving rivers greater erosional power . Rapids are areas
along the river's course…

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River, Floods and Management




Oxbow Lakes:
An oxbow lake is a horseshoeshaped lake separated from an adjacent river caused by both erosion and
deposition when erosion joins two bends together and material is deposited over the path.















Braided Channels:
Braided channels are rivers that have multiple channels and islands of…

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