Hydrographs show the relationship between a storm event and how the river behaves after.
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Different shaped hydrographs:
A 'flashy' hydrograph
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Low, flat hydrograph
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Characteristic |
Flashy hydrography |
Low and flat hydrograph |
Basin size |
Small basins transfer water to rivers quickly |
Large basins transfer water to rivers more slowly |
Drainage density (length of all the rivers in the drainage basin) |
High density speeds up water transfer |
Low density slows down transfer |
Geology |
Impermeable rocks increasing surface run-off |
Permeable rocks allow for percolation (downward movement through soil) and more groundwater flow (water travelling underground) |
Land-Use |
Urbanisation encourages faster water transfer as much of the ground is impermeable |
Forests slow down transfer as more interception occurs |
Relief |
Steep slopes speed up transfer |
Gentle slopes slow down transfer |
Soil Moisture (how much moisture can the ground hold) |
Saturated soil increases overland flow |
Dry soil soaks up water and slows transfer |
Rainfall intensity |
Heavy rain may exceed infiltration and interception rates, increasing overland flow |
Light rain is soaked up the soil more slowly, reducing transfer rate |