Modelling To Develop European Sand Dredging Guidelines

Computer predictions of the effects of commercial sea-sand dredging on coastal erosion, produced by an international team headed by Dr Alan Davies of the University of Wales, Bangor`s School of Ocean Sciences, will play a key role in developing new European Guidelines for siting commercial sand dredging activities.

Increased demand for North Sea sand is anticipated, both for use as beach and sand dune nourishment and to meet demand for sand from large-scale European construction projects. Sand extraction can exacerbate coastal erosion if dredging activities are not properly sited.

Now, coastal oceanographers and engineers from 17 European leading institutes in & European countries have embarked on a major three year EU funded project, ‘SandPit` to assess what effects sand dredging may have on the sea bed ecosystems and surrounding coastlines and to develop European guidelines for sand dredging based on the optimum size, sea depth and distance from shore of any large scale commercial sand mining operation.

The SandPit project will assess the recovery time scales for the ecosystem surrounding dredging activities, and will gauge the critical depth at which sand mining has no measurable effect on the shoreline. This will be done by dredging a full-size in the North Sea. The pit will be closely monitored to measure what happens in the immediate vicinity once the sand is extracted, to see how the ecosystem recovers and to measure any changes to the adjacent coastline. These measurements will be compared to the predications currently available, and existing computer models will be improved as necessary.

Dr Alan Davies of the School of Ocean Sciences, a coastal oceanographer with more than 20 years` experience in the physical processes of sand movement, will lead the modelling group in SandPit. The group will produce computer predictions of how waves and currents along the shoreline in any one set of circumstances might be affected by dredging and how these changes will, in turn, affect the shoreline. Model improvements will be made using field data obtained during the project, starting with experiments in the North Sea this autumn.

“Sand is transported in the water column, but the amount transported depends on variables such as the particle size of the sand, on the depth at which the dredging takes place, on currents, and in shallower waters, on wave patterns. Dredging itself, by changing the shape of the sea bed, can affect the wave size and this can have consequent effects, including coastal erosion in some situations,” explains Davies.

Current government guidelines regarding the volume and siting of dredging activities varies from country to country and are often based on information extrapolated from small-scale models. The aim of SandPit is to help towards putting future guidelines on a stronger scientific base.