FLOODING

The How, THE why -
and what you can do about it.

Flooding is simply when normally dry land becomes submerged with a large amount of water.

It’s often thought people who don’t live near the sea or a river are not at risk from flooding. However, surface water flooding, sewer flooding and groundwater flooding can occur almost anywhere.

In this section of the Reclaim the Rain website we’ll explain these types of flooding and introduce you to ways you can prevent, tackle and mitigate the harmful effects.

What is flooding and who is responsible?

01 Excess rain can lead to surface water flooding. This risk is managed by the County Councils and Internal Drainage Boards.

02 The Environment Agency is responsible for managing flood risk from rivers and the sea.

03 Homeowners have a responsibility to take steps to help protect their property and make it more resilient to flooding. Please see our property level resilience section for advice.

04 Water is contained within the soil and rock, the level of this water is known as the water table. When the water table rises above the ground it can lead to groundwater flooding. This risk is managed by County Councils and Internal Drainage Boards.

THE DIFFERENT TYPES OF FLOODING

  • Groundwater flooding

    Groundwater flooding occurs when the level of water in the rock or soil rises above ground level.

    Groundwater flooding events are most common in low lying areas where the bed rock is chalk but it can happen elsewhere, and the water does not always appear where you would expect. It is extremely difficult to predict groundwater flooding as it can happen days, weeks or even months after an intense rainfall event. There is also a lack of statistical data available to make flood risk predictions.

  • Surface water flooding

    Surface water flooding occurs when the rate of rainfall and exceeds the speed at which the land can absorb it, or exceeds the capacity of the drainage network in the area. This causes water to pool above ground.

    More people are at risk from surface water flooding than sea and fluvial flooding combined. 2.7m people in the UK are at risk of flooding from rivers or the sea but 3m are at risk of flooding from surface water. There is often limited advanced warning for these types of flood events as they can occur as flash flooding.

    This is a growing risk as the population continues to rise and urban areas (i.e. areas dominated by impermeable surfaces) continue to grow. More people are using drainage systems than ever before, and modern lifestyles consume more water than they ever did in the past.

    Impacts of climate change such as more frequent and more intense rainfall will increase the frequency and intensity of surface rainfall events, increasing the pressure on drains, sewers and water quality.

  • Sewer flooding

    Many places have separate surface water sewers and foul water sewers, however, in some areas these are combined. If there is a heavy storm the combined sewers may reach their capacity and this can cause sewage to overflow from manhole covers, drains, and even in peoples homes.

    Sewer flooding can still occur from foul water sewers in peoples homes if there is a blockage in the system. This can cause sewage to back up and overflow in peoples properties.

  • Ordinary watercourse flooding

    Ordinary Watercourses are any watercourses that are not classified as a main river. They can flow permanently or just sometimes. Flooding from an ordinary watercourse normally happens following intense rainfall. This can be made worse by watercourses not being maintained, as it reduces their capacity and ability to transfer water.

EFFECTIVE WAYS TO TACKLE
OR MITIGATE FLOODING

From clever use of the natural environment to the latest technologies, find out more about how we are able to build up our resilience against flooding.