Development and Flood Risk

Chaper 5 – Topic Policies

Section D – The Natural and Built Environment

ENV6 Development and Flood Risk

Ashford is at particular risk from fluvial flooding, as five main rivers converge in the town – the Great Stour, East Stour, Aylesford Stream, Whitewater Dyke and Ruckinge Dyke. Two flood storage reservoirs upstream of Ashford, one at Aldington on the East Stour, the other at Hothfield on the Great Stour currently protect Ashford town from fluvial flooding. These reservoirs were recently tested between December 2013 and February 2014 with the wettest winter since 1910. The region received 258% of long term average rainfall with high peak flows in local rivers. The reservoirs neared full capacity but prevented widespread flooding in Ashford.

In allocating new areas of development, the Local Plan has generally avoided areas with a high probability of flood risk and the functional floodplain. All future proposals should preferably be located in Flood Zone 1, as locating development in Flood Zone 1 means that future development is not reliant on costly fluvial flood defences that may become unsustainable in future due to climate change. It should be noted, that runoff from development within Flood Zone 1 has the potential to cause an increase in the probability of flooding if not mitigated. Therefore, any development which causes an additional flood risk by virtue of increasing runoff would need to be suitably mitigated or it will be considered unacceptable.

Policy ENV6 – Flood Risk

Proposals for new development should contribute to an overall flood risk reduction.

The sequential test and exception tests established by the National Planning Policy Framework will be strictly adhered to across the Borough, with new development preferably being located in Flood Zone 1.

Development will only be permitted where it would not be at an unacceptable risk of flooding itself, and, there would be no increase to flood risk elsewhere.

In exceptional circumstances, where the tests above cannot be met, essential transport or utility infrastructure, or other development on brownfield sites may be allowed if:

  • the development is designed to be compatible with potential flood conditions, and,
  • there are no alternative sites in a lower flood risk zone, and
  • suitable flood protection and mitigation measures are incorporated into the development appropriate to the nature and scale of risk, and
    comprehensive management and maintenance plans are in place for its effective operation during the lifetime of the development (taking account of climate change allowances), and
  • adoption arrangements are secured (where applicable) with the relevant public authority or statutory undertaker, and
  • the development would make a significant contribution to the overall sustainable development objectives of the Local Plan, such that the wider sustainability benefits of the development outweigh the flood risk, and
  • it can be demonstrated to the satisfaction of the Council and the Environment Agency that adequate resistance and resilience measures have been put in place to avoid any increase in flooding either on site or elsewhere.

A site-specific Flood Risk Assessment (FRA), endorsed by the Environment Agency, appropriate to the scale and nature of the development and the risks involved will be required inline with Planning Practice Guidance and in particular where the Strategic Flood Risk Assessment or Surface Water Management Plan, indicates there are records of historic flooding or other sources of flooding.

In all cases, development that would harm the effectiveness of existing flood defences or prejudice their maintenance or management will not be permitted.

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