Ardent Consulting Engineers were commissioned by Knight Developments Ltd to undertake a Flood Risk Assessment and 1D-2D hydraulic modelling to identify a flood alleviation scheme to support an outline planning application for the redevelopment at Elms Farm, Stansted Mountfitchet in Essex.
On obtaining detailed planning, Ardent undertook the detailed design for the flood alleviation works and secured the Environmental Permit approvals from the Environment Agency.
The scheme reduces flooding up and downstream of the site in addition to providing wider amenity and ecological benefits.
The existing site comprised of farm buildings and is located on the southern bank of the Stansted Brook which flows east to west towards the River Stort. The proposed residential development accommodates 53 units on a 2.09ha site. The development includes public open space, landscape areas (of which 2.90ha comprises wetland areas) and improved access arrangements to the surrounding parkland.
The site has a history of flooding from the Stansted Brook and is at high risk of fluvial flooding with one third of the proposed development located within Flood Zone 3. Ardent undertook hydraulic modelling of the Stansted Brook to assess the pre-development flood risk and frequency of flooding. In addition, a post development model was built to identify a flood alleviation scheme which would reduce the overall flood risk to the site and wider area while maximising developable land within the site.
To protect future residents from flooding from the Stansted Brook and ensure no increase in flood risk offsite, the following works were proposed:
• Create a development platform above the 100 year climate change flood level in the Stansted Brook
• Create 2.90ha of a wetland area to compensate for the encroachment of the raised development platform in the floodplain.
The proposed wetland significantly increases the floodplain storage volume on site above the pre development scenario
•Realign 580m of the Stansted Brook
The site’s proximity to Stansted Airport also needed to be taken into consideration by Ardent, as the floodplain compensation works also needed to ensure birds would not be attracted to the ponds which could consequently cause an increase in bird strikes to aircraft passing over the site. (No standing water in the ponds).