Flooding is a major issue in drainage basins in Wales, the UK and around the world. This section will explore what a drainage basin is, what processes operate in a drainage basin and why flooding occurs. It will also look at the effects of flooding in one UK location, and what can be done to manage and reduce the threat of future flooding.
Trees are planted near to the river. This means greater interception of rainwater and lower river discharge. This is a relatively low cost option, which enhances the environmental quality of the drainage basin.
Afforestation cannot prevent flooding but it can help reduce its likelihood.
Managed flooding (also called ecological flooding)
The river is allowed to flood naturally in places, in order to prevent flooding in other areas - for example, near settlements.
Planning (land use zoning)
Local authorities and the UK government introduce policies to control urban development close to or on the floodplain. This reduces the chance of flooding and the risk of damage to property.
There can be resistance to development restrictions in areas where there is a shortage of housing.
When planning for a new settlement in an area, this can be used to divide up the flood plain into areas which experience different levels of flood risk. Red areas will be places that are likely to experience a high degree of flood risk. Yellow areas will be places where flooding is possible but unlikely. Green areas are places where it is very unlikely that any flooding will take place.
This is effective when making decisions about new building in an area but does not work in areas that are already built up.
These are areas of land where water can wash into during a flood. They are usually found in the lower course of a river. Sluice gates will be opened to allow excess water to flow into the area and flood marginal land.
It is not always easy to find acceptable areas for this to happen – especially in areas where there are many cities.