In most coastal and estuarine settings the seabed elevation (water depth/bathymetry) changes due to the processes of sediment and sediment deposition on a daily basis.
More pronounced changes occur when wave energy can penetrate to the seabed during winter storms. Changes in seabed level greater than ~0.10 â€“ 0.15 m can be detected using conventional single- and multi-beam echo sounders. From a navigational safety viewpoint it is only changes at scales greater than this which are of importance.
However, smaller scale changes (mm – cm) are important to, amongst others, benthic habitat stability, contaminated sediment impacts, dredging impact evaluation e.g. siltation onto sensitive benthic communities, and benthic ecosystem function. Within these examples the transfer of sediments on the small scale can have considerable ecological and environmental impacts.
The Genesis 2 MHz High Resolution Recording Altimeter is a marine sonar (3.6Â° at â€“3dB beam width) capable of measuring small scale (mm â€“ cm) changes in sediment level in coastal and estuarine environments. It is based on an echo sounder which can be deployed onto fixed infrastructure or on a special frame which is designed to avoid any sediment scouring in the measurement area. The elevation resolution varies with fixed distance (2 mm , for range 20 to 70 cm; 5 mm , for range 20 to 200 cm).
The instrument is autonomous and self-logging, and can operate unattended for periods up to 9 months (variable according to sampling frequency). A second channel measures water pressure (depth), which can also be configured to sample for waves.
Source: partrac, July 31, 2012