A culverted watercourse was located beneath the site, with the outfall located downstream and offsite. Two waterbodies which linked into the culverted watercourse were also located upstream of the site on third party land.
Rainfall run-off calculations were completed for the catchment, which included taking account of the influence of the upstream waterbodies. It was necessary to measure and survey the waterbodies during the site walkover, in order to determine outfall dimensions and freeboard capacities.
The calculations revealed that the proposed development site could experience flooding from overland flows and that these would need to be accounted for in the drainage design for the site.