Finding a suitable development site can often be a challenge in itself, both from a risk and cost perspective, and this is before you’ve even placed a spade into the ground. Where at all possible, you should always aim to avoid building in a flood prone area. The three main sources of flood risk to avoid are rivers, surface water and tidal. The National Planning Policy Framework (NPPF) provides detailed guidelines as to how to avoid and manage these risks. Planning regulations also stipulate that you must consider the potential future effects of Climate Change, including the likely overall increase in heavy rainstorms, and more extreme tidal events.
Unfortunately, due to the geographic and topographical nature of the UK, it is not always possible to fully avoid all foreseeable flood risk on a development. For example, the vast amount of low-lying land located along the eastern coast of England from Grimsby to King’s Lynn are only metres above sea level. Much of this land is heavily reliant upon hundreds of kilometres of coastal defences and the artificial control of inland watercourses to reduce the risk. Furthermore, the majority of all major towns and cities in the UK are situated along the banks of rivers, or hug the coastline, which is an unwelcome legacy of the industrial revolution.
This creates a significant dilemma for planning authorities and their respective consultees (including the Environment Agency) to ensure they are not seen to overly hamper the development of housing stock that the country so desperately, and continually needs.
The granting of any planning permissions on land that has a potential to flood can be complex. Any development must prove that it has not inadvertently exacerbated flooding elsewhere. Furthermore, the development must prove that it does not cause any increased risk to life for its inhabitants or others. The key to achieving this is to use an appropriately qualified and experienced flood risk expert, who can accurately assess the present day and future flood risk. You should expect to be provided with cost effective, and realistic forward recommendations of measures, where practical, that can be successfully implemented within a development to ensure the management of flood risk.
The implementation of inadequate mitigation measures from the onset may result in the property suffering flood damage. This inevitably has a chain reaction where the property may be devalued and have difficulty in obtaining a future mortgage. Property that is not sufficiently protected within a flood prone area is quoted by the Royal Institution of Chartered Surveyors (RICS) to be of lower value than an equivalent property outside of a flood prone area. Furthermore, the insurability of the property may become problematic and unaffordable, meaning that the property owner or inhabitant cannot guarantee future reimbursement through insurance for any damaged caused by further future flooding.
Therefore, it is important to reiterate that the incorporation of the most appropriate flood mitigation measures into a development is crucial. As a developer, you should include the cost of implementing these measures within the initial overall build cost, and avoid pricing this element at a later stage. Through incorporating the most appropriate measures at the initial design stage, you can ensure that measures can be incorporated into the fabric of the development.
Examples of flood mitigation measures include flood resistance through flood proofing external walls, flood protection across entrance doors, and the sealing of any incoming utility ducts into the property. Where flooding is predicted to be of a sufficient level to potentially compromise the structural integrity of an external wall, flood resilience measures should be considered in addition.
This approach looks to allow flood water to enter the property, thus equalising the hydraulic pressure on external walls. To successfully design a flood resilient property, you must ensure that the internal materials used for floors and walls can be easily cleaned down, promoting a quick recovery after a flood has receded. The British Research Establishment (BRE) recently completed a detailed study on making a home flood resilient, and included further features such as a sump pump, easily removable furniture, non-perishable kitchen units and raised electrical sockets.
The best outcome for a development is that is can retain its overall value in future, and is fully insurable, with an affordable excess. In flood prone areas, a bank or insurer may ask you for evidence that the development is able to manage the identified risk, as part of a mortgage or insurance application. Should you have appropriately mitigated the risk of flooding, you should then be in possession of the ammunition you need to ensure your submission is granted.
Written by Simon Crowther, civil engineer and chartered water & environmental manager at Flood Protection Solutions.