Tidal flow separation at protruding beach nourishments
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Authors
Rademacher, Max
de Schipper, Matthieu A.
Swinkels, Cilia
MacMahan, Jamie H.
Reniers, Ad J.H.M.
Subjects
Advisors
Date of Issue
2017-01
Date
Publisher
American Geophysical Union
Language
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.
Type
Article
Description
The article of record as published may be found at http://dx.doi.org/10.1002/2016JC011942
Series/Report No
Department
Oceanography
Organization
Naval Postgraduate School (U.S.)
Identifiers
NPS Report Number
Sponsors
STW grant
ERC-Advanced Grant
ERC-Advanced Grant
Funder
STW Grant no. 12686: Nature-driven nourishments of coastal systems (NatureCoast), S1: Coastal Safety
ERC-Advanced Grant no. 291206 - Nearshore Monitoring and Modeling (NEMO)
ERC-Advanced Grant no. 291206 - Nearshore Monitoring and Modeling (NEMO)
Format
17 p.
Citation
M. Radermacher, M.A. de Schipper, C. Swinkels, J.H. MacMahan, A.J.H.M. Reniers, "Tidal flow separation at protruding beach nourishments," Journal of Geophysical Research: Oceans, v.122, (2017), 63-79.
Distribution Statement
Rights
This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.