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Storm Hydrographs

Factors affecting storm hydrographs

Intensity of a storm If a storm is very intense, then the top layer of soil is quickly saturated, leading to rapid runoff. This causes a short lag time, steep rising limb and high peak discharge
Long duration of a storm The top layer of soil becomes saturated, leading to rapid runoff. This causes a short time lag, steep rising limb, and high peak discharge
Antedecent rainfall Heavy rain falling on soil still saturated from previous wet weather leads to rapid runoff. This causes a short time lag, steep rising limb, and high peak discharge
Snow Water levels may fall due to snow, as water is stored on the ground. Melting causes high surface runoff, especially if ground is saturated or frozen. This causes a long lag time, a sudden steep rise in the rising limb, and high peak discharge
Porous/permeable rock types Water is regulated more slowly through the natural system, which leads to a longer lag time, lower peak discharge, and gradual rising/falling limbs
Impermeable rock types Cause higher surface stream densities, as water cannot infiltrate, which leads to high surface runoff. This leadsa to a shorter lag time, steep rising limb and high peak discharge
Size of drainage basin Small drainage basins respond more rapidly to storms than large ones, meaning they have a shorter lag time
Shape of drainage basin Water reaches the river more quickly from a rounded drainage basin than from an elongated one, meaning they have a shorter lag time
Slope angle In steep sided upland basins, water reaches the channel more quickly than gently sloping lowlands, meaning that upland basins have steeper rising limbs and a shorter lag time
Temperature High temperatures increase rate of evapotranspiration,cold temperatures freeze the ground and reduce infiltration, increasing surface runoff. High temperatures lead to a lower discharge, cold temperatures lead to increased discharge and a shorter lag time
Vegetation In summer, there are more leaves on deciduous trees, leading to more interception and evapotranspiration. Coniferous trees have less effect. This means that in summer, peak discharge and lag time are lower and longer
Land use Water runs more quickly over impermeable surfaces such as car parks and land trampled by cattle, which will reduce lag time and increase peak discharge
Urbanisation Removal of soil, compaction of ground, building of tarmac roads, drains+sewers transport water to channels rapidly, straightening of river channel, lining with concrete-lag time is reduced, peak discharge is increased. Fast water delivery-more flood risk
Created by: Rayrayy










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