Surface Water Flooding

There are often a range of options and solutions when it comes to flood risk management and mitigation at a property scale. A number of factors must be considered when determining the most suitable measures.

Firstly, the nature of the flood risk needs to be considered, including the potential sources, mechanisms, and severity of flooding. There also needs to be an appreciation of potential combined and knock-on effects of different types of flooding.

The suitability of potential options is also highly dependent on an individual site; the layout, relative ground levels, access, building construction and drainage.

Finally, there is a need to consider the client’s goals and requirements. Financial constraints and limits are an obvious consideration. The lifestyles, age and physical ability of the occupants may also influence the decision to employ passive or active flood mitigation measures. There are also personal and individual preferences which could influence which type of measures are considered most practical, efficient, and aesthetically acceptable.

The timing for implementing flood mitigation measures may also determine the preferred solutions. Refurbishment and refitting works following a flood provide an obvious opportunity to install flood resistance and resilience measures. Landscaping works in gardens and driveways also provide an ideal opportunity to consider flood risk management.

CASE STUDY

Flood Protection Solutions were instructed to investigate flood mitigation options for a semi-detached residential dwelling in Walton-upon-Thames.

Following summer storms in July 2021, the external areas of the property and neighbouring roads and areas suffered from extensive surface water flooding.

FPS undertook a Property Flood Survey to identify the risks to the property, and areas of susceptibility. The flood risk review identified that potential surface water flood depths of 0.6m could occur adjacent to the property.

The property benefits from having a solid ground floor which is raised above adjacent external ground levels, and the door thresholds were fortunately not breached during the flood event.

In order to protect the property from future floods, the Flood Mitigation Report set out a number of potential flood mitigation options, including:

• Property Flood Resilience measures such as flood doors or flood barriers

• Sealing all low-level entry points such as pipework and cables

• Strategic options to manage surface water

Following completion of the survey, the client decided to explore strategic options to improve the drainage adjacent to the property as part of ongoing landscaping works within their garden. The client subsequently undertook percolation testing within their rear garden and infiltration rates were found to be good. The client has subsequently installed a new geo-cellular soakaway system which will help manage accumulations of surface water adjacent to the property.

There is not often a one-fits-all solution to flood risk management. In this instance the landscaping works provided an opportunity for measures to be implemented, and ground conditions allowed a passive, and aesthetically unobtrusive solution to be achieved. Should flooding at the property ever become worse in the future, there remains scope to implement some of the alternative and additional measures identified within the Flood Mitigation Report.

If your property has experienced flooding, or you are concerned about the risks, contact Flood Protection Solutions to see how we may be able to assist.