1. 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
  2. Shape
    Elongated basin will produce a lower peak flow and longer lag time than a circular one of the same size
  3. Slope
    Channel flow can be faster down a steep slope therefore steeper rising limb and shorter lag time
  4. Rock Type
    Permeable rocks mean rapid infiltration and little overland flow therefore shallow rising limb
  5. 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
  6. 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
  7. Drainage Density
    A higher density will allow rapid overland flow
  8. 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
  9. 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
Card Set