Physical factors affecting flood hydrograph dynamics

Drainage basins all have a variety of characteristics. The range of characteristics can affect how likely a river within the basin will flood. Let's take a look at these different flood hydrograph dynamics.

Shape

A circular shaped drainage basin leads to rapid drainage whereas a long drainage basin will take time for the water to reach the river.

Topography & relief

The steeper the basin the more quickly it drains. Indented landscapes will collect water and reduce runoff rates, reducing the amount of water reaching the river channel.

Heavy Storms

Runoff will increase after soil field capacity is met which means water will reach the channel quicker.

Lengthy rainfall

This leads to the ground being saturated and runoff will increase which means water will reach the channel more quickly once soil capacity has been reached.

Snowfall

Until the snow melts, the water is held in storage but when the snow melts this can lead to flooding.

Vegetation

This can reduce discharge as it intercepts precipitation. Roots of plants can also take up water that goes into the soil. Seasonally, in the UK the vegetation will reduce discharge in the summer whereas in the winter it will have less of an impact due to less foliage being present on trees.

Rock type

The underlying geology varies within drainage basins and can be permeable (allowing water through) or impermeable (not allowing water through). Impermeable rocks encourage greater amounts of surface runoff and a more rapid increase in discharge than permeable rocks.