Policy information sourced from the Watford Local Plan 2021-2038.
NE9.4: Flood Risk and Mitigation
When located within areas identified as being at risk of flooding, applicants are required to demonstrate how appropriate and effective mitigation measures have been integrated into the scheme, including management of residual flood risk. Proposals located within flood zones, need to meet the requirements of the Sequential and Exception Tests. Only water compatible and essential infrastructure will be permitted within Flood Zone 3b (functional floodplain). Essential infrastructure must also first pass the Exception Test to be located within Flood Zone 3b. Developers should seek to increase the extent of Flood Zone 3b where possible and appropriate. To demonstrate compliance with the Exception Test, a flood resilient design and emergency planning considerations will need to be accounted for, over the lifetime of the development including:
- The development to remain safe and operational under flood events;
- Safe evacuation and/or safely remaining in the building under flood conditions;
- Key services must continue to be provided under flood conditions; and
- Buildings are to be designed for quick recovery following a flood.
Any development within Flood Zones 2 and 3, and those over one hectare in Flood Zone 1, should use a Flood Risk Assessment to show how they have considered flood risk beyond the site boundaries, including cumulative impacts arising from other developments. It must be demonstrated that the development provides wider sustainability benefits to the community that outweigh flood risk (informed by the evidence in the Strategic Flood Risk Assessment) and that where possible, development will reduce flood risk overall. Proposals for development in the floodplain must demonstrate that suitable flood compensation storage will be provided to avoid any net loss in floodplain. Additionally, all new development within flood zones require an assessment of the impact of climate change on flood risk on site and elsewhere.
Developers should seek to provide an undeveloped buffer zone of eight metres between the top of the bank of any Main River and any new development (including formal landscaping, sports fields, footpaths, lighting and fencing).
Proposals located in areas where waterways have been culverted or altered should seek to re-naturalise the river and surroundings, improve water storage and enhance riparian habitats, in line with requirements to meet Water Framework Directive objectives and the Thames River Basin Management Plan. There is a presumption against the use of hard engineering, including gabions.
For any development within eight metres of a culvert, the developer must demonstrate that they have sought to de-culvert, as well as undertake a survey of the culvert to assess its exact location, condition and whether it is commensurate with the lifetime of the development or demonstrate how it will be repaired/upgraded. Flood defences and Main Rivers adjacent to development sites must be maintained, repaired or replaced by the developer for the lifetime of the development. For any development within eight metres of a main river, the developer must demonstrate that access to the river and banks will still be possible for maintenance and emergency works.
Groundwater protection
Where a proposal is located within a Groundwater Source Protection Zone, applicants will be required to demonstrate there will be no significant impacts or risks to controlled waters. If a potential impact is identified, appropriate mitigation measures need to be incorporated as part of the scheme. Within Source Protection Zone 1 (SPZ1), infiltration via deep bore soakaways will not be acceptable, other than when a drainage and hydrogeological risk assessment shows this to be the only viable option and that any risks to groundwater will be adequately mitigated. Certain discharges into the ground may require an Environmental Permit.
For more information, please see the Watford Local Plan 2021-2038.