Storm Hydrograph
A storm hydrograph (or flood hydrograph) is a detailed time-series graph showing the relationship between rainfall and river discharge during a single precipitation event. It displays the baseflow, rising limb, peak flow, and falling limb, revealing how quickly a catchment responds to rainfall.
Real World
After Storm Desmond hit Cumbria in December 2015, the River Greta's hydrograph showed a lag time of under two hours and a dramatic peak — evidence of rapid surface runoff over waterlogged ground.
Exam Focus
Always explain lag time in terms of catchment characteristics (slope, land use, soil type) — never just describe the hydrograph shape without linking to causes.
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