The CSM is an in situ device for measuring the erosion shear stress of exposed intertidal sediments. The CSM device has undergone substantial modification since its original conception in 1989 (Paterson 1989, George 1995, Tolhurst et al in press), and is currently manufactured by Sediment Services for the Sediment Ecology Research Group.
|
The CSM consists of a water filled chamber 30 mm in diameter that is pushed into the sediment. The jet of water comes from a downward directed nozzle in the chamber. The velocity of the jet is increased systematically through each experiment. Bed erosion is inferred from the drop in the transmission of infrared light across the chamber caused by the suspension of sediment. The erosive jet maintains a well-defined core region to the bed so erosion occurs over a small area, which enables the device to detect small-scale spatial variations in stability. The rapidity of deployment and the short time required for a stability measurement to be taken make the CSM ideal for measuring temporal variations in sediment stability.
The latest version (CSM Mk IV) is fully automatic; with computer control of pressure settings, pulse duration and interval. Data is recorded directly to an onboard CPU (central processing unit) and downloaded to a computer for analysis. The CSM utilises a vertical jet of water to erode the sediment surface (Paterson 1989). |
