ALLOWANCE FOR FORMATION OF MEGA SAND WAVES ON THE SEABED IN THE DESIGN OF FAIRWAYS IN ESTUARIES WITH STRONG CURRENTS
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How to Cite

Molen, W. van der, Watson, H., & Taylor, D. (2020). ALLOWANCE FOR FORMATION OF MEGA SAND WAVES ON THE SEABED IN THE DESIGN OF FAIRWAYS IN ESTUARIES WITH STRONG CURRENTS. Coastal Engineering Proceedings, (36v), sediment.35. https://doi.org/10.9753/icce.v36v.sediment.35

Abstract

The declared depth in port access channels is often maintained by dredging and monitored by regular bathymetric surveys. However, at remote sites these activities are not cost-effective and the channel depth would need to be defined based on the surveyed depth plus an allowance for sedimentation and variability in bed levels. This allowance can especially be significant in estuaries with strong tidal currents, where mega bedforms, including sand waves, develop on the seabed due to the prevailing strong current flows. The mega sand waves are highly mobile and fluctuate in height as they migrate over the seabed. Mega sand waves and mega ripples with a height up to approx. 3.2 m were observed in multi-beam bathymetric survey undertaken in the offshore entrance to the Geba River estuary in Guinea Bissau. Supramax bulk carriers with a draft of 11-12 m are planned to transit this area on departure from a proposed phosphate export terminal located further upstream in the estuary.

Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/5Gmy9yQkfno
https://doi.org/10.9753/icce.v36v.sediment.35
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References

Schmitt, Mitchell, Ramsay (2007). Use of swath bathymetry in the investigation of sand dune geometry and migration around a near shore ’banner’ tidal sandbank. Coastal and Shelf Sediment Transport, 274, 53-64.

PIANC (2014). Harbour approach channels design guidelines. Report No 121.

Yalin, Da Silva (2017). Fluvial processes. 2nd Ed. CRC Press.

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