Project 5: Sub-tidal survey of the Exe Estuary
European Marine Site Client: Environment Agency & Exe Partnership


The Exe Estuary is designated as an SSSI because of its biological and geomorphological interest. The estuary is also listed as a RAMSAR site, the margins of which encompass the waters, foreshore, low-lying land, marshes, plus the sand dunes of Darwlish Warren, and the spit extending seaward from the mouth of the estuary. Rocky outcrops are a prominant feature of the shoreline along the eastern shoreline to Straight Point.

A seabed mapping study was commissioned by the Environment Agency, on behalf of co-funding partners, and part financed under the under the EU North West INTERREG IIIB Cycleau Program. The aim of the project was to produce bathymetric and biotope maps of the sub-tidal estuary. Underwater video footage was required of the range of sub-tidal habitats within the estuary , and the collective data was to be incorporated into GIS, for ease of user access.














Shoreline of the Exe Estuary

Hydrosurveys were awarded the contract to survey a sub-sea area, using a combination of interferometric swath technology and acoustic ground discrimination, together with video and benthic sampling techniques.

The following images show a short section of the entrance channel at Exmouth, surveyed and analysed using different methods :

A) Conventional colour contoured bathymetry (single beam)
B) Coloured digital terrain model (multibeam)
C) Sidescan image (sidescan backscatter)
D) Clasified texture map of sediments & aquatic vegetation.
E) 3D digital terrain model of submerged rocky shoreline