Draft Local Plan October 2012

Water and Flood Risk

7.34 Water is a precious and finite resource. There is a need to protect not only the sources of water (both surface and underground) and the quality of water, but also the general environment associated with the water system. The use of policies in this Local Plan (e.g. on environmental protection, green infrastructure, biodiversity and sustainable construction) and adherence to national guidance and policy will assist in achieving the objectives of the Water Framework Directive and actions of the Thames River Basin Management Plan, particularly the requirement to protect and improve the status of water bodies, including their ecological value.

7.35 The River Thames and its tributaries contribute to the character and local distinctiveness of the District and provide a valuable resource for wildlife, fisheries, landscape, tourism, public access and water related activities. Development that would have an adverse impact on this resource will be resisted.

7.36 Historically, settlements have tended to locate within river corridors, using the river as a source of water, food, transport and energy (the River Windrush, for example, was fundamental to Witney's blanket industry). After heavy rain, however, many of these water courses flood. Flooding from surface water drainage, ground water and sewers also occurs. A Strategic Flood Risk Assessment (SFRA) has been prepared in conjunction with the Environment Agency to update the information on flooding in West Oxfordshire and includes an assessment of the likelihood of additional flooding as a result of climate change. A countywide study has also been undertaken into flooding from surface runoff, groundwater and ordinary watercourses: the Oxfordshire Flood Risk Assessment.

7.37 In terms of development in flood risk areas, a sequential, risk-based approach will be followed, steering vulnerable development to areas at lower risk of flooding. (The Government has published technical guidance, alongside the NPPF, giving further advice on flood risk.) Inappropriate development will not be allocated or permitted in flood risk zones 2 and 3 (which have higher probability of flooding), areas at risk of surface water flooding or areas with a history of groundwater flooding, or where it would increase flood risk elsewhere, unless there is over-riding need, an absence of suitable alternatives and flood risk can be satisfactorily addressed. All development at risk of flooding will require a flood risk assessment and must be designed to be flood resilient and resistant, for example, through raising floor levels, designing buildings to withstand the effects of flooding and achieve safe access and escape routes.

7.38 National advice, the SFRA and the West Oxfordshire Design Guide provide guidance on the use of Sustainable Drainage Systems (SuDS): drainage systems that mimic natural patterns and can ease surface water run-off, helping to avoid soil erosion, control pollution and enhance biodiversity. The use of SuDS will be required as part of any new development. Advice should be sought from the Environment Agency or the SuDS approval body.

7.39 The need for water management is especially relevant for West Oxfordshire, not just associated with the issue of flood risk (as exemplified by the summer floods of 2007) but equally water scarcity at times of drought. The District lies within an area of 'serious' water stress where there are limited water resources and yet a high and growing demand for water. Core Policy 3 - Prudent Use of Natural Resources seeks to maximise the efficient use of water.

CORE POLICY 21 - Flood Risk

Flood risk will be managed using the sequential, risk-based approach, set out in the National Planning Policy Framework, of avoiding flood risk to people and property where possible and managing any residual risk (taking account of the impacts of climate change). In assessing proposals for development:

  • the Sequential Test* and, if necessary, the Exception Test** will be applied
  • all sources of flooding will need to be addressed and measures to manage or reduce their impacts, onsite and elsewhere, incorporated into the development proposal
  • appropriate flood resilient and resistant measures should be used
  • sustainable drainage systems to limit run-off will be integrated into the site design, maximising their habitat value and ensuring their long term maintenance
  • a site-specific flood risk assessment will be required for all proposals of 1ha or more and for any proposal in Flood Zone 2 and 3 and Critical Drainage Areas
  • only water compatible uses and essential infrastructure will be allowed in a functional flood plain (Flood Zone 3b)
  • land required for flood management will be safeguarded from development and, where applicable, managed as part of the green infrastructure network, including maximising its biodiversity value.

* The aim of the Sequential Test is to steer new development to areas with the lowest probability of flooding. Development should not be allocated or permitted if there are reasonably available sites appropriate for the proposed development in areas with a lower probability of flooding.

** If, following application of the Sequential Test, it is not possible, consistent with wider sustainability objectives, for the development to be located in zones with a lower probability of flooding, the Exception Test can be applied if appropriate. For the Exception Test to be passed:

a) it must be demonstrated that the development provides wider sustainability benefits to the community that outweigh flood risk, informed by the Strategic Flood Risk Assessment; and

b) a site-specific flood risk assessment must demonstrate that the development will be safe for its lifetime taking account of the vulnerability of its users, without increasing flood risk elsewhere, and, where possible, will reduce flood risk overall.

Both elements of the test will have to be passed for development to be allocated or permitted.