Presentation on theme: "The Flood hydrograph A brief explanation- By Paul P., Dean M., George W., James S., Chris O."— Presentation transcript:
The Flood hydrograph A brief explanation- By Paul P., Dean M., George W., James S., Chris O.
Shows variation in discharge(m 3 per sec) over time. Storm hydrograph shows effects of rainfall input. The average levels represent the base flow of water produced from groundwater supply. The two limbs are called the rising and recession limbs while the time delay between max rainfall and max river discharge is called the lag time.
The flood hydrograph
A-DISCHARGE B-LAG TIME (Affected by rock permeability and vegetation interception) C-PEAK DISCHARGE D-ZONE OF FLOOD RISK E-NORMAL (BASE) DISCHARGE F-RECESSION LIMB G-RISING LIMB
How is it affected? Intensity and duration of rainfall Seasonal weather conditions Residual moisture eg. Saturation increases angle of rising limb Vegetation cover (affects interception) Size and slope angle of drainage basin (lowers and increases peak discharge respectively) Urbanisation eg. Concreting increases speed of water reaching the channel