Policy Option 04 - Flood Risk

  • Many communities across Oxfordshire have been affected by flooding. Flooding causes both immediate and long-term disruption to people's lives, businesses and wildlife.
  • The risk of flooding is expected to increase in future years, with climate change altering weather patterns and increasing the severity and frequency of extreme weather events. It is important to ensure that the impacts of climate change on flood risk are appropriately managed and mitigated so that Oxfordshire's communities, businesses and natural environment are resilient, with the ability to adapt and thrive in the long-term, to 2050 and beyond.
  • The Oxfordshire Authorities are commissioning a Strategic Flood Risk Assessment (SFRA) to inform the production of the Oxfordshire Plan. The SFRA will provide up-to-date information on flood risk, from all sources, and will be based upon the latest evidence and modelling, including the latest climate change projections. The SFRA will consider the individual and cumulative impacts on flood risk of growth proposed through the Oxfordshire Plan in combination with growth proposed in other plans (including Oxfordshire's adopted local plans and plans for adjoining areas as appropriate). Information in the SFRA will be used to apply a sequential, risk-based approach to the location of development. It will also identify infrastructure and other adaptations necessary to manage flood risk to 2050 and beyond. The SFRA will be published at the next stage of consultation (Regulation 19).
  • In considering flood risk management and adaptation in Oxfordshire, the priority will be to work with natural processes wherever possible, utilising natural flood management methods. This approach can help to deliver wider benefits for people and wildlife by helping to restore habitats, improve water quality and increasing resilience to climate change.
  • As natural flood management works best when a 'catchment-based approach' is taken (where efforts are coordinated to manage the flow of water along the whole length of a river catchment from its source to sea), the Oxfordshire authorities will work with the Environment Agency and other stakeholders to implement this approach.
  • Ambitious policies in the Oxfordshire Plan would enable the local planning authorities to work together to secure a transformational change across the entire Thames catchment.

Policy Options

  • We could leave it to local plans to set policies in relation to flood risk; but increasing resilience to climate change is a strategic cross-boundary planning matter. It is considered appropriate to include a county-wide flood risk management policy in the Oxfordshire Plan. This is not the preferred option as there is a risk that local plans might take different approaches to flood risk. This could result in less certainty and clarity for developers and communities. It may also make it more difficult to meet proposed ambitions around the delivery of transformational change and increasing resilience to climate change.

Preferred Policy Option

  • The preferred approach is for the Oxfordshire Plan to provide a strategic planning framework for managing flood risk in Oxfordshire. This framework would set out flood risk management and drainage requirements relevant to development across Oxfordshire. It would be consistent with the opportunity that the Oxfordshire Plan represents to deliver long-term transformational change and to address the impacts of climate change, with a specific emphasis on nature-based solutions.
  • There is a significant amount of existing development in the functional floodplain (Flood Zone 3b) in Oxfordshire. The preferred policy approach incorporates recommendations from the Environment Agency to increase the resilience of existing development in Flood Zone 3b. In taking this approach, the impact on design (specifically building heights) needs to be considered. However, given the severity of the risks associated with flood risk, the preferred approach prioritises flood resilience. If this approach is consistently applied, then over time building heights would become more aligned as increasing numbers of homes are rebuilt or raised. Local plans could provide further detail as appropriate.

Policy Option 04: Flood Risk

The Oxfordshire Plan would require the following:
1) Development to take account of both its impact on flood risk and the potential impacts of flood risk on the development and its future occupiers/users.

2) Development to utilise natural flood management and drainage methods, including:
a) the use of appropriate green infrastructure; 
b) the use of sustainable drainage systems (SuDS);
c) the use of design measures (such as the use of permeable external surface materials);
d) maximising opportunities to restore natural river flows and floodplains;
e) avoiding building over or culverting watercourses;
f) and removing existing culverts wherever possible.

3) Major development to comply with Oxfordshire County Council's Local Standards and Guidance for Surface Water Drainage on Major Development in Oxfordshire (published November 2018) or any subsequent standards/guidance which might supersede this. Additional SuDS features may be required where there are impact pathways on habitats of national and international importance.

4) Where existing built development in Flood Zone 3b is proposed to be redeveloped or extended, opportunities would be taken to ensure that the new development is resilient to flooding over its lifetime. Replacement buildings in Flood Zone 3b to have finished floor levels above the 1 in 100 year flood level, plus an allowance for climate change.

5) Flood risk evidence to support local plans to identify areas of the functional floodplain (Flood Zone 3b) where householder development and small non-residential extensions are having a cumulative impact on flood risk. Opportunities to manage development in Flood Zone 3b that would otherwise be permitted under the General Permitted Development Order 2015 (as amended) to be considered.

6) The Oxfordshire authorities to work with the Environment Agency and other stakeholders to support a catchment-based approach to flood risk management across the Thames catchment area. Schemes that utilise natural flood management methods and deliver wider benefits for Oxfordshire's communities, wildlife and businesses would be supported and prioritised.

7) Flood risk management and mitigation measures identified within the SFRA to be incorporated within the policy framework as appropriate.

Alternative Policy Option 04-1

  • Include a strategic flood risk policy in the Oxfordshire Plan but reduce the scope of this policy. For example:

    i) Support the use of sustainable drainage systems (SuDS) but do not require compliance with specific local guidance/standards; and/or

    ii) Support increasing the resilience of existing development in Flood Zone 3b, but do not set specific requirements.
  • This is not a preferred option as there is a risk that local plans might set different flood risk management and drainage requirements across Oxfordshire. This could result in less certainty and clarity for developers and communities. It may also make it more difficult to meet proposed ambitions around the delivery of transformational change and addressing the impacts of climate change.

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