Flooding in Hounslow

Types of flooding

Surface water flooding

This occurs as a result of high intensity rainfall where excess water ponds at low points. It is intensified in urban areas where there is impermeable land because water is unable to enter the drainage systems at sufficient rates or infiltrate below the ground.

Fluvial flooding

This occurs when heavy or prolonged periods of rain cause a river to exceed its capacity and overflow onto adjacent land. The Environment Agency has duties and powers in relation to main rivers in the UK.

Tidal flooding

This occurs during extremely high tide and/or storm surge events. The risk of tidal flooding in Hounslow is relatively low due to the presence of the Thames Tidal Defences (TTD), most notably the Thames Barrier, which currently protect properties up to a 1 in 1000 year storm event.

Flooding from artificial sources

This occurs when the failure of infrastructure or human intervention results in flooding. Artificial sources include reservoirs, canals, water retention ponds, docks and other artificial structures.

Sewer flooding

This occurs when the amount of rainfall entering the sewer network is too large to be contained due to a lack of sewer capacity. This can be caused by hydraulic overload (an increase in flow), meaning the system has to deal with an event larger than that which it was designed to manage. This can also be caused by the failure of key infrastructure such as pumps and valves. The system in Hounslow is owned and operated by Thames Water.

Groundwater flooding

This occurs when the underground water table rises, which can cause water emerging through the ground. This type of flooding typically occurs after extensive periods of heavy rainfall.