In January 2022, Exo were appointed to carry out a multibeam bathymetry survey focussing on a stretch of the River Orwell in order to provide reliable data to dredging operations occurring at Woolverstone Marina.  The survey area was approximately 130ha, and the survey was conducted over the course of 3 days, in order to maximise time spent surveying at high spring tides.  

We used our Arvor 18 vessel for this survey, including the Norbit IWBMS 400khz sonar head system and the Valeport Swift Sound velocity profiler. 

After the survey was completed, our dedicated team of hydrographic analysts processed and cleaned the data and sent it to the client to inform on dredging depth requirements.  

Our swift response to the client’s query and efficient surveying time allowed us to deliver the data on time and to a high standard.

As part of the Brightlingsea Dredging and Restoration project, Exo conducted dual-frequency bathymetric and unmanned aerial vehicle (UAV) photogrammetric surveys throughout the site, during high and low water spring tides respectively. The high-resolution datasets were then merged across the overlapping intertidal zone (with an approximate tidal range of 5m) using specialist software to provide a comprehensive map of levels throughout the creek.

Applying the client’s requested target depths for each dredge area, accurate dredge volumes were calculated and used to match with the storage volumes of restoration sites selected following the comparison of historic and current saltmarsh extents. In addition to project design, the data obtained also supported project planning through the identification of priority areas, provided baseline data for continued environmental monitoring and assisted in the formulation of a long-term management plan for the Brightlingsea Harbour Authority.

The combination of these survey techniques provided excellent data coverage for logistically challenging sites located at the land-water interface such as the intertidal zone.

In November 2021, Exo were appointed to carry out a multibeam bathymetry survey of Baltic Wharf, in the River Crouch, Essex. The survey focused on determining the depth to chart datum around a 100mx15m long jetty, at a distance of 50m on the outside and 25m on the inside of the structure.  

Using our wealth of experience in both conducting bathymetry surveys as well as working in similar environments, we chose to carry out the survey at the highest state of tide to give our multibeam system the best beam swath angle coverage, which allowed us to ‘see’ more of the seabed.   

Using the Norbit IWBMS system mounted on our 18ft Arvor, we were able to complete the survey on time and within budget and process and send the final cleaned data set to the client within one day.