ABSTRACT: Wind flow and sediment transport over a vegetated coastal foredune, Greenwich Dunes, Prince Edward Island, Canada.

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Abstract

Measurements of wind flow and the intensity of sediment transport were made across the stoss slope of a vegetated foredune at Greenwich Dunes over a six week period in May and June, 2002. The dunes here are about 8-10 m high and have an average slope of about 35 degrees. The dune slope has a nearly continuous cover of marram (Amophila breviligulata) but the toe to the dune was largely bare due to wave scarping and there was a low, discontinuous embryo dune located just seaward of the toe at the top of the beach. Wind speed measurements were made along a profile from the top of the beach to the crest using an array of both continuously recording and totalising cup anemometers. The intensity of sand transport was measured with three Sabatech saltation probes. The potential for sediment transport up the foredune is controlled in part by the interaction between the wind angle and dune slope. Potential transport is enhanced by flow compression and speed-up over the dune which reaches about 200% for direct onshore winds and decreases to zero as the wind angle moves towards shore perpendicular. On the other hand, potential transport rates are inhibited by the gravitational effects of the steep slope angle for onshore winds and this decreases as winds trend towards shore perpendicular. Sediment transport frequency and intensity decrease rapidly within the vegetation cover and there is an exponential decrease in saltation intensity with increasing vegetation cover. The results confirm annual deposition measurements which show most sediment reaches the dune crest in late fall when there is a large reduction in vegetation cover.

Bibliography of Canadian Geomorphology