Tidal flow separation at protruding beach nourishments

Radermacher, M.; de Schipper, M.A.; Swinkels, Cilia M.; MacMahan, Jamie; Reniers, A.J.H.M.

doi:10.1002/2016JC011942

Tidal flow separation at protruding beach nourishments

Title

Tidal flow separation at protruding beach nourishments

Author

Radermacher, M. (TU Delft Coastal Engineering; WaveDroid)
de Schipper, M.A. (TU Delft Coastal Engineering; Shore Monitoring & Research)
Swinkels, Cilia M. (Deltares)
MacMahan, Jamie (Naval Postgraduate School)
Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics; Deltares)

Date

2016

Abstract

In recent years, the application of large-scale beach nourishments has been discussed, with the Sand Motor in the Netherlands as the first real-world example. Such protruding beach nourishments have an impact on tidal currents, potentially leading to tidal flow separation and the generation of tidal eddies of
length scales larger than the nourishment itself. The present study examines the characteristics of the tidal flow field around protruding beach nourishments under varying nourishment geometry and tidal conditions, based on extensive field observations and numerical flow simulations. Observations of the flow field around the Sand Motor, obtained with a ship-mounted current profiler and a set of fixed current profilers, show that a tidal eddy develops along the northern edge of the mega-nourishment every flood period. The eddy is generated around peak tidal flow and gradually gains size and strength, growing much
larger than the cross-shore dimension of the coastline perturbation. Based on a 3 week measurement period, it is shown that the intensity of the eddy modulates with the spring-neap tidal cycle. Depth-averaged tidal currents around coastline perturbations are simulated and compared to the field observations. The occurrence and behavior of tidal eddies is derived for a large set of simulations with varying nourishment size and shape. Results show that several different types of behavior exist, characterized by different combinations of the nourishment aspect ratio, the size of the nourishment relative to the tidal excursion length, and the influence of bed friction.

Subject

beach nourishment
flow separation
tidal flow
Sand Motor

To reference this document use:

http://resolver.tudelft.nl/uuid:d4bbee17-b99f-458f-9b19-9199a007e6f2

DOI

https://doi.org/10.1002/2016JC011942

ISSN

2169-9275

Source

Journal Of Geophysical Research-Oceans, 122 (1), 63-79

Part of collection

Institutional Repository