Groundwater flooding support | Oxfordshire County Council

Groundwater flooding support

Information on Groundwater flooding

What is Groundwater?

Groundwater is defined in the Flood and Water Management Act 2010 (FWMA) as ‘all water which is below the surface of the ground and in direct contact with the ground or subsoil’.  This water occupies the cracks and pores of permeable rocks, soils and gravels.   

What is Groundwater flooding?

Groundwater flooding can happen when the water table (level of water) within the rock or soil that makes up the land surface rises.  Once the water reaches ground-level water starts to emerge on the surface, this will not necessarily result in flooding of properties. 

The most common geological areas to be susceptible to groundwater flooding are; chalk, limestone and sandstone, along with sand and gravels in river valleys.

Groundwater flooding can be difficult to predict as it will usually occur within days or weeks after heavy or prolonged rainfall. This type of flooding can last several weeks or months causing disruption to road and sewer networks.  Groundwater flooding can occur on its own as well as in combination with other sources of flooding (surface or fluvial).

Who is responsible for Groundwater flooding?

Lead Local Flood Authorities (LLFA's) have responsibilities for local flood risk including groundwater flooding; this is covered in the FWMA 2010.

The Environment Agency has a responsibility to have a strategic overview of all sources of flooding.  The Environment Agency provides a groundwater alert / warning service, more information on this can be found on the GOV.UK website

This booklet from the Environment Agency contains more information on flooding from groundwater.

Mapping the risk of groundwater flooding is complex and is currently not available from the Environment Agency.

LLFA Responsibilities

The Flood and Water Management Act 2010 requires the LLFA to prepare a local flood risk management strategy where they co-operate with other risk management authorities and have powers to carry out local flood risk management duties with regard for surface water runoff, groundwater and ordinary watercourses throughout Oxfordshire.  

As a LLFA, Oxfordshire County Council have powers and duties to which include:

  • Commissioning works to manage flood risk from surface water runoff or groundwater.
  • Give consent for any proposed changes to ordinary watercourses.
  • Record, investigate and publish reports on significant flood events in the county.
  • Record flood assets and identify those who are responsible for maintaining them.
  • Designate any features which they do not maintain and have a significant impact on flood risk so they cannot be removed or replaced without consent (Flood structures can include; garden walls, culverts, bridges etc.).
  • Ensure that developments drain in a manner which does not increase flood risk elsewhere, as well as trying to reduce the risk of flooding throughout the county.      
Last reviewed
06 October 2016
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