Factors affecting hydrographs

Factors affecting hydrographs

1. Climate

   • Precipitation type/intensity
     • short, intense rainstorms produce rapid overland flow due to quick soil saturation rates which decreases infiltration and cause steep rising limb
   • Temperature and evapotranspiration
     • extreme temperatures mean ground is frozen or baked which reduces infiltration and increases overland flow.
     • hotter climates mean more evapotranspiration so lower peak discharge

2. Morphology

   • Basin size and shape
     • circular basins have higher peak discharge (water reaches river at same time), longer lag times (water takes longer to reach river)
     • smaller basins have shorter lag time which means more flooding will occur
   • Slopes and relief
     • shorter lag time when relief is steeper
     • during storms, water travelling down steep slopes is moving too quick to infiltrate and so there is higher overland flow and steeper rising limb

3. Geology

   • Porosity and permeability
     • high porosity and permeability means more soil capacity and more infiltration so reduced overland flow and shallower rising limb
   • Rock type
     • sedimentary- porous, increase store and infiltraton
     • metamorphic- not porous, can be permeable (less storage and infiltration)
     • igneous- not porous, increase discharge

4. Land use

   • Urbanization
     • increase in concrete (impermeable) surfaces, less infiltration and more runoff. Steep rising limb
   • Afforestation
     • more interception= gentle rising limb. More porous surfaces= more storage