Rivers, Floods and Management: River Drainage and Storm Hydrograph

Mind Map by , created over 5 years ago

A Levels Geography (Physical Geography-AS) Mind Map on Rivers, Floods and Management: River Drainage and Storm Hydrograph, created by Andrew_Ellinas on 04/01/2014.

Created by Andrew_Ellinas over 5 years ago
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Rivers, Floods and Management: River Drainage and Storm Hydrograph
1 What is River Discharge?
1.1 The volume of water in a channel passing a particular point in a given period of time.
1.2 Values are expressed in cumecs (cubic metres per second)
1.3 The calculation is: discharge (m3 per second) = cross-sectional area (m2) x velocity (metres per second)
2 What Factors Affect River Discharge?
2.1 Distance Downstream: In humid environments, river discharge increases downstream. Main reason for increase in water are caused by tributaries joining the main river.
2.2 Climatic Characteristics: Snowfall results in time delay as it is being stored for a long time until snowmelt happens and there is a sudden surge in discharge. Temperature affects evaporation rates and vegetation growth
2.3 Land Use: Afforestation reduces discharge and make it more constant. Urbanisation increases discharge because water is transferred rapidly over impermeable surfaces such as tarmac-and through pipes and sewers.
2.4 Water Abstraction (Removal): This is for domestic use and the irrigation of crops, this reduces discharge. This can be seasonal, with greater demand for water in summer months.
2.5 Channel Modification: Constructing a reservoir regulates the discharge and makes it more constant. The channel itself might also be modified to reduce flood risk e.g. channel straightening and enlargement tend to increase discharge.
3 The Storm Hydrograph
3.2 This is a graph that shows the discharge of a river following a storm event
3.3 Characteristics that affect hydrographs: