Flood Risk and Drainage Impact Assessment in Dunholme, Lincolnshire
Jun 20, 2013

RAB Consultants has recently prepared a Flood Risk Assessment in support of a proposed residential development in Dunholme, Lincolnshire.

Although the site is located within the Environment Agency’s Flood Zone 1 outline, the proposals involve the development of 70 residential dwellings across approximately 4 hectares of greenfield land. The developer must therefore consider the management of surface water runoff.

Through data collection, consultations and data analysis, the assessment concluded that the site currently has a low risk of fluvial (river), surface water, sewer and groundwater flooding. There are no reservoirs or canals in close proximity to the site.

The proposals are expected to increase the sites impermeable surfaces. RAB Consultants therefore prepared a drainage assessment which:

* Calculated the total permeable and impermeable areas across the site, pre- and post-development;

* Determined the sites existing (greenfield) rates and volumes of surface water runoff during a number of modelled return periods;

* Provided a conceptual drainage design using modelling software to design a Sustainable * Drainage System (SuDS) component which is capable of managing surface water runoff on site and is able to reduce runoff to a greenfield rate when leaving the site. The design considered a number of extreme flood events and also climate change.

A final report has been submitted to the client and is currently being submitted as part of the outline planning application.