RIDGE-RUNNEL MIGRATION

Jens Figlus, Nobuhisa Kobayashi, Christine Gralher

Abstract


The recovery of beaches after a storm can be influenced significantly by ridge-runnel migration. Ridges are made up of large volumes of sand which is important for the coastal sediment budget. The experiment described in this paper gives an insight into the complex hydrodynamics and sediment transport mechanisms related to onshore ridge-runnel migration. Detailed water free surface elevation, fluid velocity and sediment transport rate measurements were taken in a mobile bed wave flume with a focus on the effect of water ponding and runnel drainage on the profile evolution. The measured results have been used to calibrate the time-averaged numerical cross-shore model CSHORE. The model has the capability to deal with the effect of a pronounced profile depression (water-filled runnel) forming on the intermittently wet and dry zone of the beach. Results of the experiment compared with the corresponding numerical model computations show that the rapid onshore migration of a ridge-runnel system under fairly energetic wave conditions can be computed with CSHORE but further improvements of the model are necessary.

Keywords


beach recovery; beach morphology; moveable bed experiment; sediment transport; numerical modeling; ridge and runnel; morphodynamics; profile evolution

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