Water hides its shape. A bathymetric survey measures the bed under the water so you know how deep it is, how much it holds and how much silt has settled since it was built.
What a bathymetric survey measures
- Bed levels across the whole water body
- Water-spread area at the surveyed water level
- Storage capacity (volume) at that level
- Silt build-up when compared with an earlier survey
- Cross-sections and longitudinal sections of rivers and canals
How the survey is done
A survey boat carries a single-beam echo sounder and a GNSS receiver. The echo sounder sends a sound pulse down and measures the time it takes to return from the bed, which gives the depth. The GNSS receiver records where each depth was taken. The boat runs planned lines across the water so the whole bed is covered.
Before starting, temporary benchmarks (TBMs) are fixed on the bank and the water surface level is recorded. Depth below the water surface is converted to bed level using this water level, so every sounding is on the same datum as the land survey around it.
From soundings to capacity
The processed soundings are turned into a bed surface. The volume between this surface and the water level gives the storage capacity. Contours of the bed show deep and shallow areas, and repeating the survey after some years shows where silt is collecting.
Where it is used
- Village ponds and talabs: capacity and desilting quantities
- Reservoirs and dams: sedimentation and storage checks
- Rivers: cross-sections for bridges, embankments and flood studies
- Intakes and pipelines crossing water
What you should receive
- Bed contour plan in AutoCAD and PDF
- Depth map and water-spread area
- Capacity at the surveyed water level
- Cross-sections and L-section
- XYZ data of all soundings
- Report with TBMs, water level and method
Planning a pond, reservoir or river project? Share the location and the purpose (capacity, desilting, design or flood study) and we will plan the survey.