There are many human and physical causes of flooding:
Risk |
Human or Physical? |
Explanation |
Urbanisation |
Human |
Concrete is impermeable so precipitation falls to the ground and stays there as surface run off |
Steep relief |
Physical |
Precipitation falls but due to the steep angle of the land, the force of gravity doesn’t allow the precipitation to infiltrate into the soil. Therefore the rain runs as surface run off to the bottom of the hill. |
Low bridge/obstruction |
Human |
If there is an increase in the river’s discharge, then the low bridge can serve as an obstruction in the river which increases the probability of it overflowing. |
Deforestation |
Human |
There is limited opportunity for precipitation to be intercepted by vegetation. Therefore it is infiltrated into the soil faster, which speeds up the saturation of the soil. Therefore making it more likely that there will be surface run off. |
Impermeable rock |
Physical |
Some rock types do not easily allow water to be infiltrated. Therefore the water will remain on the surface as surface run off and create a flood. |