Flood Hydrographs

• Flood Hydrograph- represents rainfall for the drainage basin and discharge of the river on a graph.
• Example of a Flood Hydrograph

  
• Discharge- volume of water passing through a cross-sectional point of the river at any point in time/Cumecs. Made up of baseflow and stormflow.
• Rising Limb- the line that represents the discharge increasing
• Falling Limb- the line that represents the discharge decreasing
• Lag Time- time between peak rainfall and peak discharge
• Baseflow- level of grounwater flow
• Stormflow- comprised of overland flow and throughflow
• Bankfull discharge- maximum capacity of a river before its banks burst.
• Flashy Hydrograph- short lag time, steep rising and falling limb, higher flood risk, high peak discharge.
• Subdued Hydrograph- long lag time, gradual rising and falling limb, lower flood risk, low peak discharge
• Natural effects on the Hydrograph- High rainfall intensity, antecedent rainfall (occurs before the rainfall studied), impermeable underlying geology, high drainage density, small basin, circular basin, low temperatures, precipitation type, vegetation cover
• human effects on the hydrograph- Urbanisation, pastoral farming, deforestation.