Service Communautaire d'Information sur la Recherche et le Développement - CORDIS

Cohesive strength meter calibration for salt marshes

The small-scale spatial variations in the erosion threshold of exposed subtidal and intertidal sediments can be measured using the cohesive strength meter (CSM) (Tolhurst 1999). The CSM is comprised of an on board computer, water reservoir, filter assembly, digital and analogue pressure gauges, optical sensor head, and first stage diving cylinder with hose attached. The chamber (diameter 30mm) is placed onto the sediment surface and secured using a clamp stand and filled with water. A jet of water is directed towards the sediment surface within the chamber from a height of 2cm above the sediment surface. The velocity of the water jet is increased systematically with each jet over a period of time (dependent on which test protocol is selected).

A drop in transmission of the infrared light, caused by the suspension of sediment across the chamber, determines the erosion threshold. Data is recorded directly to an onboard central processing unit and can then be downloaded to a PC for further analysis. However, a new version of the dive was required for salt-march studies since the erosion resistance of march sediment can be high. A high pressure CSM system was therefore produced (Sediment Services, SME) but this required a new calibration since the old calibration was only relevant to the low-pressure system.

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Reported by

Gatty Marine Laboratory UNIVERSITY OF ST ANDREWS
Gatty Marine Lboratory, East Sands
United Kingdom