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Area
- Large basins receive more precipitation than small therefore have larger runoff
- Larger size means longer lag time as water has a longer distance to travel to reach the trunk river
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Shape
Elongated basin will produce a lower peak flow and longer lag time than a circular one of the same size
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Slope
Channel flow can be faster down a steep slope therefore steeper rising limb and shorter lag time
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Rock Type
Permeable rocks mean rapid infiltration and little overland flow therefore shallow rising limb
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Soil
- Infiltration is generally greater on thick soil, although less porous soils eg. clay act as impermeable layers
- The more infiltration occurs the longer the lag time and shallower the rising limb
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Land Use
- Urbanisation - concrete and tarmac form impermeable surfaces, creating a steep rising limb and shortening the time lag
- Afforestation - intercepts the precipitation, creating a shallow rising limb and lengthening the time lag
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Drainage Density
A higher density will allow rapid overland flow
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Precipitation & Temperature
- Short intense rainstorms can produce rapid overland flow and steep rising limb
- If there have been extreme temperatures, the ground can be hard (either baked or frozen) causing rapid surface run off
- Snow on the ground can act as a store producing a long lag time and shallow rising limb. Once a thaw sets in the rising limb will become steep
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Tidal Conditions
High spring tides can block the normal exit for the water, therefore extending the length of time the river basin takes to return to base flow
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