AQA AS Geography - Rivers, Floods and Management Content (FULL NOTES)

I hope this is helpful :).

Everything on the rivers content is according to the official aqa geography specification. Case study's regarding flooding and flood management are not included in this download.

Resources used: 

1. CGP AS-Level Geography Complete Revision Guide

2. www.geographyas.info

3. AQA Geography AS Student Book by Simon Ross, Bob Digby, Russell Chapmen and Dan Crowling.

4. My Revision notes - AQA AS Geography by Michael Raw

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  • Created on: 26-04-13 10:45
Preview of AQA AS Geography - Rivers, Floods and Management Content (FULL NOTES)

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Geography Revision Notes ­ Rivers, Floods and Management
AS level Geography
Rivers, Floods and Management
Water Balance
Water balance is worked out from inputs
(precipitation) and outputs (channel discharge
and evapotranspiration)
Wet seasons = increased precipitation which
exceeds evapotranspiration. Creating water
surplus.
Drier seasons = precipitation is lower than
evapotranspiration. Ground stores are depleted
as water is used and flows into the river channel.
At the end of the dry season there's a deficit (shortage) of water in the ground.
Ground stores are recharged for the next wet season (i.e. Autumn).
Equation is shown as - (P=O+E+S)
The Hydrological Cycle
A drainage basin - Dynamic open system
Closed System - no inputs or outputs.
Catchment Area - area of land that is surrounding the river that is drained.
Watershed - water transfer, water supply
are contained within this area.
Inputs & Outputs:
Inputs - water coming into the system
Outputs - water leaving the system
Input e.g. ­ Precipitation
Output e.g. - Evapotranspiration, River
Discharge
Storage & Transfers:
Storage's - water stored in the system
Transfer's - water moving from one place to another
Storage e.g. ­ Interception
Transfer e.g. ­ Percolation
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Geography Revision Notes ­ Rivers, Floods and Management
Factors affecting Discharge
Discharge is the volume of water (in cubic metres, m³) that flows in a river per
second.
Calculations:
Depth x Width = Cross Sectional Area
Distance x Time = Velocity
Velocity x CSA (Cross Sectional Area) = Discharge
Storm Hydrograph
Storm hydrograph - representation to
show the volume of water at a certain
point in a river changes over a period of
time.…read more

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Geography Revision Notes ­ Rivers, Floods and Management
Storm Hydrograph (Factors)
3…read more

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Geography Revision Notes ­ Rivers, Floods and Management
River Processes ­ Vertical and Lateral Erosion
The energy of a river flowing downhill causes erosion. The bed and banks of a
river can be eroded - making the river longer, deeper and wider.
A river's channel is eroded laterally and vertically. The intensity of lateral and
vertical erosion is dictated by the stage in the river's course
In the upper stage of the river's course there is little horizontal erosion and lots
of vertical erosion.…read more

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Geography Revision Notes ­ Rivers, Floods and Management
The Hjulström Curve
Capacity and Competence
Rivers Capacity - The maximum volume of load that a river can carry at a
specific point in its course.
The load of a river can be divided into different categories according to its
particle size.
Rivers Competence ­ biggest sized particle that the river can carry.…read more

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Geography Revision Notes ­ Rivers, Floods and Management
Cross Profiles
Cross Profile - shows the cross section of a river channel or river valley.
The valley cross profile changes during different stages of a river's long profile.
Upper stage - Steep V shape valleys , Vertical erosion
Middle Stage - Wider valleys, Lateral Erosion, Deposition forming flood plains.
Lower stage - wide valleys, gentle sloping sides.…read more

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Geography Revision Notes ­ Rivers, Floods and Management
The speed that a river flows at is affected by the efficiency of a river's channel.
The efficiency of a river's channel is dependent on a few factors.…read more

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Geography Revision Notes ­ Rivers, Floods and Management
Potholes
Potholes are small circular depressions in the river bed.
Potholes form when pebbles become trapped in small hollows and vertical
eddies as they develop, drilling the pebble into the bed in a circular motion ,
forming the pothole by corrasion.
Potholes will increase the rivers wetted perimeter; therefore it decreases the
Hydraulic Radius, affecting channel efficiency.
Waterfalls
Found when a river flows over a band of hard resistant rocks causing erosion to
softer rocks.…read more

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Geography Revision Notes ­ Rivers, Floods and Management
They form where the gradient of the river is steep and the bed is composed
mainly of hard rocks.
The formation of rapids will increase the wetted perimeter due to its irregular
steps and its hard rocks that cause channel roughness.
Meanders
Meanders form when alternating riffles (shallow water) and pools (deep water)
form along a river channel.
These riffles and pools form at equally spaced intervals from about 5x the width
of the river bed.…read more

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Geography Revision Notes ­ Rivers, Floods and Management
of sedimentary load, a steep gradient and where there is a lot of variation in
discharge of the river changes regularly.
When the volume of load exceeds the river's capacity or the discharge of the
river drops, aggradation occurs the islands of sediment (eyots) form.
There is better channel efficiency as the hydraulic radius has been increased.
Floodplains
Floodplains are large, flat expanses of land that form on either side of a river.…read more

Comments

Roshni

This is a really detailed document... and it looks veryyy helpful! I am using these notes to add to my notes, Thankyou much :))

Marta Kohls

Excellent revision guide! Highly recommended! :) 

yathavan

Awesome work!

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