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Factors Influencing Storm Hydrographs (Precipitation & Temperature…
Factors Influencing Storm Hydrographs
Drainage Density
A higher density will allow rapid overland flow.
Land Use
Urbanisation
Concrete and tarmac form impermeable surfaces, creating a steep rising limb and shortening lag time.
Afforestation
Intercepts the precipitation, creating a shallow rising limb and lengthening the time lag.
Soil
Infiltration is generally greater on thick soil, although less porous soils e.g. clay acts as impermeable layers.
The more infiltration occurs the longer the lag time and shallower the rising limb.
Rock Type
Permeable rocks mean rapid infiltration and little overland flow therefore shallow rising limb.
Slope
Channel flow can be faster down a steep slope therefore steeper rising limb and shorter lag time.
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.
Area
Large basins receive more precipitation than small therefore have largdr runoff.
Larger size means longer lag time as water has a longer distance to travel to reach the trunk river.
Shape
Elongated basin will produce a lower peak flow and longer lag time than a circular one of the same size.
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 stone producing a long lag time and shallow rising limb. Once a thaw sets in the rising limb will become steep.