Bathymetric surveys allow us to measure the depth of a water body as well as map the underwater features of a water body. Multiple methods can be used for bathymetric surveys including multi-beam and single-beam surveys, ADCPs, sub-bottom profilers, and the Ecomapper Autonomous Underwater Vehicle. We use bathymetric surveys for many different types of research including flood inundation, contour of streams and reservoirs, leakage, scour and stabilization, water-quality studies, dam removal, biological and spill, and storage and fill in reservoirs and ponds.
Bathymetric data is used for a range of purposes including:
Charting and ship navigation
Fisheries management
Environmental management, including establishing baseline data to support environmental monitoring
Determination of maritime boundaries
Alternative energy assessments (i.e. to support offshore wind and wave energy assessments)
Research into coastal processes and ocean currents, for example tsunami modelling
Assessment of environmental considerations for marine geology resource management including the identification of geohazards, such as underwater landslides
Bathymetric surveys allow us to measure the depth of a water body as well as map the underwater features of a water body. Multiple methods can be used for bathymetric surveys:
Multi-beam surveying: A multibeam echo sounder attached to a boat sends out a wide array of beams across a "swath" of the waterbody floor. As the beams are bounced back from the waterbody floor, the data is collected and processed. The processed data can be viewed in real time on the boat during the survey. Multi-beam surveying is generally done in larger water bodies.
Single-beam surveying: Rather than sending out a wide set of beams, single-beam bathymetry measures the water depth directly under the boat. Single beam echosounders produce a single line of depth points directly under the equipment Single-beam surveys are generally used for smaller water bodies.
Acoustic Doppler Current Profiler (ADCP): ADCPs are used throughout USGS to measure streamflow. ADCPs measure water velocity by transmitting sound waves which are reflected off sediment and other materials in the water. Data collected from ADCPs can then be used to for bathymetric mapping.
Sub-bottom profilers: Sub-bottom profilers are most commonly used to view the layers of sediment and rocks under the water body floor. A transducer sends a sound wave to the water body floor. This sound wave can penetrate the water body floor. The data returned from the sound waves can be mapped to show the layers beneath the water body floor.
Ecomapper Autonomous Underwater Vehicle: The Ecomapper can collect detailed bathymetric data, down to one-foot contours, in places that are difficult to reach with boats. The Ecomapper uses side-scan sonar and a Doppler velocity log.
Satellite data can be used to produce maps showing general features over a large area at low resolution. Satellite altimetry measures the height of the ocean surface. If there are hills/mountains on the sea floor, the gravitational pull around that area will be greater and hence the sea surface will bulge. This measurement can be used to show where the seafloor is higher, and this can be used to produce maps showing general features over a large area at low resolution.