Observations and Predictions of Wave Runup, Extreme Water Levels, and Medium-Term Dune Erosion during Storm Conditions

Abstract

Monitoring of dune erosion and accretion on the high-energy macrotidal Vougot beach in North Brittany (France) over the past decade (2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014) has revealed significant morphological changes. Dune toe erosion/accretion records have been compared with extreme water level measurements, defined as the sum of (i) astronomic tide; (ii) storm surge; and (iii) vertical wave runup. Runup parameterization was conducted using swash limits, beach profiles, and hydrodynamic (Hm0, Tm0,-1, and high tide water level-HTWL) data sets OPEN ACCESS J. Mar. Sci. Eng. 2015, 3 675 obtained from high frequency field surveys. The aim was to quantify in-situ environmental conditions and dimensional swash parameters for the best calibration of Battjes [1] runup formula. In addition, an empirical equation based on observed tidal water level and offshore wave height was produced to estimate extreme water levels over the whole period of dune morphological change monitoring. A good correlation between this empirical equation (1.01Hmoξo) and field runup measurements (Rmax) was obtained (R 2 85%). The goodness of fit given by the RMSE was about 0.29 m. A good relationship was noticed between dune erosion and high water levels when the water levels exceeded the dune foot elevation. In contrast, when extreme water levels were below the height of the toe of the dune sediment budget increased, inducing foredune recovery. These erosion and accretion phases may be related to the North Atlantic Oscillation Index.

Characterizing storm response and recovery using the beach change envelope: Fire Island, New York

“…Zeigler et al, 1959;Lee et al, 1998;Houser et al, 2008;Castelle et al, 2015;Suanez et al, 2015) to sandy beaches (Wright and Short, 1984;Sexton and Hayes, 1991;Morton, 2002;Priestas and Fagherazzi, 2010) and dunes (Saunders andDavidson-Arnott, 1990, Hesp, 2002;Psuty et al, 2005;McLean and Shen, 2006;Houser, 2012;Plant and Stockdon, 2012;Lentz et al, 2013;Houser et al, 2015;Weymer et al, 2013;Wilson et al, 2015). These studies assess change using a variety of beach metrics including island volume, shoreline and dune position, and profile topography from consecutive elevation surveys (i.e.…”

“…recovery with respect to what reference point). Furthermore, where storm-driven change is typically determined by the hydrodynamics of the event including waves, tides, and storm surge (Lee et al, 1998;Stockdon et al, 2007;Sallenger, 2000;Suanez et al, 2015), recovery can be affected by both hydrodynamic conditions (e.g. Scott et al, 2016) and aeolian sediment transport (e.g.…”

Wave runup estimations on platform-beaches for coastal flood hazard assessment

“…On a macrotidal environment, Suanez et al (2015) obtained good empirical runup relationships between observed and predicted runup using the slope of the active section of the beach. Their experiment was conducted during 5 years to enhance the range of conditions (wave heights, periods and beach slopes) under which the formula was parameterized with a slope value varying depending on hydrodynamic and tidal conditions, especially the water level.…”

“…Such basic formulae require, however, a study of the beach morphology, since in natural settings, the beach slope is not easy to identify (Holman and Sallenger 1985;Nielsen and Hanslow 1991;Cariolet and Suanez 2013;Suanez et al 2015).…”

“…Laboratory experiments on a smooth and impermeable slope have also been made by Mase (1989), who proposed an imaginary slope taking into consideration the cross-sectional configuration of the foreshore and the defense structures (Mase et al 2013), as opposed to the concept of imaginary slope of Saville (1958), defined by a line passing through two points, on the seabed at wave breaking and on the beach at the wave uprush limit. For coastal management purposes, determination of a mean profile slope in order to use an empirical formula to predict erosion events without knowing the exact associated slope at the precise moment of the runup event can also be used (Suanez et al 2015). Mather et al (2010Mather et al ( , 2011 also defined a representative nearshore slope by calculating the ratio of water depth to an offshore distance point defined by the depth of closure of the profile.…”