Lands to West of Broad Street Green, Essex
Parmarbrook first got involved with this particular site in 2014 when Persimmon Homes approached us to help them understand the constraints associated with a large Greenfield site in Maldon Essex. A site walkover on a waterlogged and flooded site soon after made it clear that site drainage and flood risk was going to be a big challenge to the development.
As our Land Development team developed a site Flood Risk Assessment (FRA) it was evident that the site was located in an area suffering from severe overland surface water flows due to large swathes of rural agricultural land to the north of the site. Developing the site to provide 145 new residential dwellings in a safe and resilient manner would require a holistic and regional approach to Flood Risk in the area.
Working closely with the Essex SUDS Department as Lead Local Flood Authority (LLFA) during the planning process, we coordinated with the design team to amend the site layout and to locate wide soft landscaped buffers along the site boundaries, where the overland flows entered the site. We designed the levels of these landscaped areas to essentially act as detention zones during heavy storm periods and hold the overland flows, preventing the site from being inundated with floodwaters. When flooding dissipated the held floodwaters were then released gradually back into the drainage network of the area.
We also worked closely with the landscape team to ensure these detention zones were designed so that they kept their amenity value during non-flood events and could be used by site end-users as part of the overall site landscape vision.
Early sketch showing flood detention zone
As well as keeping the site safe and flood free, the proposals also had the added benefit of reducing flood risk to the existing edge of town properties adjacent to the development site, which is always a welcome benefit from introducing site mitigation measures.
Aided by negotiation with Essex SUDS, our detailed FRA for the site was approved by both the Planning Authority and Environment Agency which was a significant milestone considering the high flood risk classification of the site. The key, as always, is early negotiation and engagement with client and key stakeholders on complex issues such as Flood Risk.
As is common on many of our projects, we follow the development of the site into detailed design stages, in particular the Civil Engineering Design. This is inherently linked to our previous work at planning stage where we outlined our drainage strategy for the site. Building on our knowledge of the site geology and past flooding we knew infiltration was not feasible on site. This allowed us to tailor our design to provide on-site surface water attenuation in order to comply with Essex SUDS requirements. It also enabled us to integrate a new surface water pond into the site landscaping, again, adding to the site amenity and bio-diversity characteristics before outfall to an existing watercourse.
This in addition to the flood mitigation detentions areas have ensured a robust and integrated approach to the site’s drainage while being sympathetic to the existing drainage regime of the surrounding area.
As the demand for new homes increases, the pressure to develop on constraint sites will become a more frequent option for developers. As demonstrated above, our early engagement on projects can create real and workable mitigation measures which unlock this potential and add value to our client’s projects.
Author: Mark Gordon- Head of Land Development
Project: Lands to West of Broad Street Green
Client: Persimmon Homes
Architect: Grafik Architecture