MANAGEMENT OF AEOLIAN SAND TRANSPORT ON A DIKE, DUNKIRK SEAPORT, FRANCE

The shoreline of Dunkirk Seaport partly consists of a macrotidal beach oriented WSW-ENE backed by a 6 km long coated dike called “digue du Braek”. Aeolian sand transport was estimated on asphalt by means of sand traps. Also, time-averaged wind speed profiles were measured using cup anemometers under various wind velocities and directions along a transversal profile on the dike and the upper beach. High rates of sand transport enabled the setup of different kinds of experimental windbreaks on asphalt, in order to test potential dune formation on this kind of substrate. Under oblique onshore winds, it was regularly observed that amounts of sand captured in the traps placed on the dike were more important than those in traps placed on the upper beach. These results were related to sand sources: windblown sand captured on the dike originated from the coastal dunes developed at the dike toe, while sand trapped on the upper beach came from the tidal zone were aeolian transport is limited by complex intertidal bar-trough topography. It also appeared from the topographic surveys carried out on the windbreaks that although their location seemed to play a major role on the amount of sand captured, fences and synthetic fabrics deployed on sandy surfaces were also able to trap windblown sand on the seaport dike.

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Estimating Annual Onshore Aeolian Sand Supply from the Intertidal Beach Using an Aggregated-Scale Transport Formula

Journal of Marine Science and Engineering ◽

10.3390/jmse6040127 ◽

2018 ◽

Vol 6 (4) ◽

pp. 127 ◽

Cited By ~ 4

Author(s):

Leonardo Duarte-Campos ◽

Kathelijne Wijnberg ◽

Suzanne Hulscher

Keyword(s):

Moisture Content ◽

High Tide ◽

Sand Transport ◽

Wind Gust ◽

Aeolian Sand ◽

Aeolian Transport ◽

Aeolian Sand Transport ◽

Sand Supply ◽

Transport Prediction ◽

High Tide Line

In this paper, we explore an approach for annual-scale transport prediction from the intertidal beach, in which we aggregate the surface conditions of the intertidal beach, in particular moisture content and roughness, and use hourly monitoring data of wind speed and wind direction. For our case study area (Egmond Beach, The Netherlands), we include Argus video imagery in our analysis to assess the occurrence of aeolian sand transport. With the approach described to determine a characteristic moisture content value for aeolian transport, we obtained surface moisture values of 1.2% to 3.2% for wind average and wind gust respectively, implying that we need a quite dry beach. This indicates that the main area for aeolian transport corresponds to the upper part of the intertidal source, most likely the region between mean high tide line and spring high tide line.

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Using Video Monitoring to Test a Fetch-Based Aeolian Sand Transport Model

Journal of Marine Science and Engineering ◽

10.3390/jmse8020110 ◽

2020 ◽

Vol 8 (2) ◽

pp. 110 ◽

Cited By ~ 1

Author(s):

Pam Hage ◽

Gerben Ruessink ◽

Zilla van Aartrijk ◽

Jasper Donker

Keyword(s):

Wind Velocity ◽

Transport Model ◽

Transport Rate ◽

Beach Sand ◽

Sand Transport ◽

Winter Period ◽

Aeolian Sand ◽

Aeolian Transport ◽

Aeolian Sand Transport ◽

Strong Winds

Transport of beach sand to the foredune by wind is essential for dunes to grow. The aeolian sand transport rate is related to wind velocity, but wind-based models often overpredict this transport for narrow beaches (<100 m). To better predict aeolian sand transport, the fetch-based Aeolus model was developed. Here, we qualitatively test this model by comparing its transport-rate output to visual signs of aeolian transport on video imagery collected at Egmond aan Zee, the Netherlands, during a six-month winter period. The Aeolus model and the Argus images often agree on the timing of aeolian transport days, except when transport is small; that is not always visible on the Argus images. Consistent with the imagery (minimal signs of aeolian activity in strong winds), the Aeolus model sometimes predicts the actual transport to be smaller than the potential transport. This difference is largest when wind velocity is large, and its direction is cross-shore. Although transport limitations are not predicted to be common, the results suggest that their effect on the total transport in the study period was substantial. This indicates that the fetch distance should be taken into account when calculating aeolian transport for narrow beaches on longer timescales (>weeks).

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