what causes a catchment to flood?

climate, geology, soil, vegetation and human influences

what is a stable network condition?

something that doesn't change on a timescale on which floods occur

what is a variable network condition?

something that changes over time relating to how much river is being stored in the catchment

why is a long catchment less likely to flood that a short, circle one?

rain has a larger distance to cover

what are examples of variable basin conditions?

soil depth, type and structure, vegetation cover, geology, and indirect human activities

what are examples of network conditions?

drainage networks

what are examples of channel conditions?

channel characteristics and human river regulation

what is the return period of a flood on a floodplain?

3 years

what is the return period for floods in reservoirs in remote areas?

150-1000 years

what is a return period?

how often a flood of a particular magnitude will be exceeded on average

what is the return period equation?

return period (years) = (n+1)/m (n = number of years in record, m = rank)

what is a unit hydrograph?

a characteristic storm hydrograph for a catchment, it shows the direct relationship between effective rainfall and quickflow

what are the causes of low flows?

the balance between precipitation and evapotranspiration, geology and soil, afforestation and water use