Water and Effluent Treatment Magazine
Issue link: https://fhpublishing.uberflip.com/i/579379
october 2015 WET NEWS 19 ThE CoNCEpT • the government has set a target of building 200,000 new homes annually before 2020 • the potential sources of flooding are diverse including: rivers over topping, tidal surges and damaging waves, surface water flooding from intense rainfall, over flowing sewers, and rising groundwater levels as observed in the recent flooding of 2013/14 • climate change predictions see flooding set to increase with knock-on effects to ground stability and erosion • Homes at high risk of flooding may have difficulty obtaining suitable insurance, and for homes built before 2009 the government and insurance industry have developed the new Flood re scheme, expected to go live in April 2016 • Land at risk of flooding is under pressure for development • A key part of the new strategy is to implement SuDs of which infiltration to the ground is the preferred option NEED To KNoW 1 It is estimated that one in six homes across the UK are at risk from flooding – approximately 5.2 million properties 2 2.8 million properties are susceptible to surface water flooding 3 the government has said all new developments of ten homes or more, and major commercial developments, must consider sustainable drainage systems to manage surface water run-off 4 SuDs aim to alleviate drainage issues by storing or re-using surface water at the source, and decreasing flow rates to watercourses 5 the system can protect and enhance water quality by reducing pollution from surface run-off ThE VERDICT • As a result of the government policy new developments will no longer be able to automatically connect to surface water drainage or combined public sewers • the greatest benefit to general flood risk is if all run-off is infiltrated on site W ith the government's target of building 200,000 new homes annually, the development of housing in areas at risk of flooding is increasingly being approved by planning authorities in a bid to tackle the UK's housing shortage. Although planning policy has looked to avoid inappropriate development in flood risk areas, some development is inevitable, particularly in high growth areas. Whilst many proposals have been rejected due to flood risk, hundreds of planning applications have been approved as developers have provided more information to better define the flood risk and adapted the design of the build. Flood plains comprise 12% of the land in England according to the Government Advisory Body Committee on Climate Change (CCG). However, it is urban areas in particular that are posing a more significant and local flood risk because of the reduction in the amount of rainfall which can soak away into the ground, essentially increasing the speed and volume of flooding. Greater pressure Whilst traditional systems, which historically combined surface water and foul sewerage drainage, have been replaced in many areas with separate sewers, greater pressure will subsequently be placed on urban drainage with increased development and climate change. In some areas, water companies with ageing infrastructure may need significant investment to provide sufficient drainage capacity to support housing growth. It is not always possible to provide defences to keep floodwater away from buildings and infrastructure. Measures to do so may negatively impact people, wildlife or even the economy and they could just increase flooding elsewhere. Increased demand for housing and limited available space means that it may be inevitable that properties will be built on sites that have some risk of flooding, even aŒer measures have been taken to reduce the risk. It is therefore important that new developments are designed to be resistant or resilient to flooding. It is not just new developments that are at risk, however. It is estimated that over five million existing properties across the UK could be affected by flooding – around one in six homes. Even those homes and businesses situated far from common sources of river and coastal flooding may also be at risk from groundwater or surface run-off, so it may not always be obvious. Issue Surface water, groundwater and overflowing sewers are increasingly common causes of flooding, and with 2.8 million properties currently thought to be at risk of surface water flooding, it is a very real issue. Naturally, flooding cannot be controlled in its entirety. In recent years, there has been a move away from flood defence strategy towards flood risk management, where the onus has been placed on mitigating and minimising the impact of flooding. Since the Flood and Water Management Act 2010, local authorities have a responsibility as the Lead Local Flood Authority (LLFA), which means they must coordinate flood risk management across the borough, including the drawing up of local flood risk management strategies. The strategies must outline policies to mitigate flood risk from any development, and demonstrate how the LLFA will work with local planning authorities to reduce risk. • Housing demand is increasing but limited available space means it may be inevitable that properties will be built in areas where there is risk of flooding, says eSI's Paul ellis. The challenge: Tackling housing development in flood risk areas It is estimated that over five million existing properties across the UK could be affected by flooding INSIGHT FLooD rISK mAnAgement