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Flood risk and planning: We need to learn from the past

Rachel Glossop

Flood risk manager, Hull City Council

Historically towns and settlements have developed alongside water for the resource, navigation, trade and wealth water could bring. Construction was fairly basic with buildings able to cope with flooding and those buildings of significance, such as churches, were usually located on the highest land. Centuries later housing types have changed and the buildings we see today are less able to cope with the challenges of flooding. Up until 1992 the planning system had largely not considered flood risk when it came to new development. The Department of Environment produced planning Circular 30/92 which gave the newly formed National Rivers Authority (NRA) some powers to comment on planning applications within a specified distance of a main river alongside consenting powers under the Land Drainage Act to regulate development and construction.

This was then replaced with Planning Policy Guidance Note 25 in 2001 following extensive flooding in the UK in 1999 and 2000. This strengthened the requirements to consider flood risk in new development by mapping the country into flood risk zones. The Environment Agency (previously the NRA) became a consultee on planning applications within the high risk areas with the aim of preventing inappropriate development in the floodplain. The document became a Planning Policy Statement and now forms part of the National Planning Policy Statement.

This production of documents and formation of a consultee role for the Environment Agency was demonstration of the fact that flood risk had become an important material planning consideration in the decision making process.

Whilst this addressed the flood risk to new development by ensuring that if the flood risk could not be mitigated then new development should not be permitted, it did not always address the issue of flood risk from new development in the form of additional surface water run-off created by constructing impermeable surfaces. There was no consistent approach in different Environment Agency and Local Authority Areas in terms of consultation on surface water drainage and what was required. Sustainable Drainage (SuDs) was promoted in PPG25 but with no clear steer as to who regulated, adopted or maintained.

You can find out more about sustainable drainage and how it helps to manage surface water in this animation from Susdrain: https://www.youtube.com/watch/LMq6FYiF1mo

Drainage swale in Hull. Image: Hull City Council

Surface water lagoon in Hull. Image: Hull City Council

Following the 2007 floods, which were predominantly surface water, the Pitt Review concluded that surface water needed appropriate consideration in the planning process. The Flood and Water Management Act 2010 formed the Lead Local Flood Authorities and a statutory consultee role in planning on surface water for major development.

In a nutshell what all of this blurb means is that in the past people understood water and built their homes and businesses near water but lived with water. This included raising buildings or accepting that flood ingress was possible but minimising damage. There then followed decades of development where there seems to have been little thought on the impacts flood and drainage could have. Homes were built in the floodplain with no mitigation, surface water was not restricted and there was little thought to the infrastructure required.

The present day situation is that to build in the high flood risk areas there are many hurdles that quite rightly need to be crossed. Firstly developers have to show there are no other appropriate sites at lower risk, this is called the sequential test. Whilst this sounds sensible it is worth noting that existing settlements are usually in the high risk areas, the low risk are the top of hills where there is no existing infrastructure or utilities so not always appropriate in terms of sustainability. Secondly a Flood Risk Assessment needs to be produced which looks in detail at the risk to the development and provides what mitigation is required to make the development safe for the lifetime of the development. This includes measures like raising floor levels, flood proofing and a place of safety. If these cannot be incorporated into the development then planning consent should not be granted. Thirdly a Drainage Assessment should be provided which has assessed in detail the existing drainage on the development site and will provide a drainage strategy to mimic the existing in ensuring that run-off rates are the same or less and have the same outfall points. This is to ensure there is not additional pressure of receiving watercourses or sewers. This should be done through the use of SuDs.

If you are buying a new property, ask the developer to show you the Flood Risk Assessment and Drainage Assessment and how they have complied. If they can’t our advice would be not to buy the property. It’s is the biggest investment you will make in your life and developers need to play their part in managing flood risk.