Flood investigations

As the Lead Local Flood Authority (LLFA) for Wandsworth, one of the Council’s duties is to investigate flood events that occur within in its area as it deems necessary.

Upon learning of a flood event within Wandsworth, the Council will consider whether an investigation should be carried out, under Section 19 of the Flood and Water Management Act (2010), in order to determine:

  • which authorities and individuals have relevant flood risk management functions
  • whether each of those authorities or individuals have exercised, or are proposing to exercise, those functions in response to the flood

The Investigating Officer will follow the established ‘Flood Investigations Protocol’ whereby it will be determined whether an investigation should be carried out, taking into account the available resources and significance of the event.

Adopted Flood Investigation Protocol

The investigating officer will use the following guidance to determine whether an investigation should be carried out. This will be based on the assessment of the consequences of flooding that are considered to be sufficiently serious in terms of risk to loss of life, residential & commercial property, critical infrastructure, transport, cultural sites and environmental sites.

The Council's thresholds for formal investigation of residential and commercial properties are as follows. A formal flood investigation will be carried out if one or more of the following occurs:

  • If 1 or more residential or commercial properties flood internally* as part of a single flood event
  • If 5 or more residential or commercial properties are flooded externally (within the curtilage of the property) as a result of a single event in the same location
  • If 1 or more residential or commercial properties has flooded externally more then twice within a single year

*Definition of internal flooding: Where water crosses the threshold of a commercial or residential building.

Note: The Council will not investigate flooded basesments where the cause is groundwater flooding entering through cracks in the basement walls or floor.

It is not the responsibility of the Investigating Officer to resolve the flooding issue or provide solutions, however they will investigate the cause and notify any relevant authority and those affected. Private landowners also have responsibilities in relation to land drainage and riparian ownership.

If, following significant widespread flooding in the borough, where a number of incidents meet the thresholds for investigation, the investigations will be undertaken on a priority basis. This will take into consideration factors such as the number of properties affected, the extent, depth and duration of the flooding, the history of flooding, and the impact on infrastructure such as roads.

Where an investigation has been carried out a ‘Flood Investigation Report’ will be completed and a summary will be published on this webpage. 

Upon receipt of a flood incident report, the Council will endeavour to undertake and complete a flood investigation report within six months. However this may not be possible following extensive flooding across the borough.

Pages in Flooding