Sellindge is situated east of Ashford on the M20. Due to its location, there is significant development planned in the immediate future. The catchment suffers from flooding and there is a lack of capacity for future developments. RAA were commissioned by Southern Water to undertake a strategic review of the catchment and sewerage network. The objective of this study were costed options to deal with the flows from the planned development and the alleviation of the existing flooding problems.
During this study a number of options were investigated, which included a new gravity sewer to a neighbouring catchment and a new rising main directly to the sewage treatment works. As part of this study a LiDAR survey was carried out to obtain accurate topographical data. The LiDAR data was then used to create both a digital Terrain Model (DTM) and a Digital Elevation Model (DEM).
The availability of the accurate DTM and DEM allowed the proposed alignment of new gravity sewers and rising mains to be optimised so as to avoid deep excavations during construction while avoiding the numerous ancient woodlands which cover this area.  This study was completed in 2007.