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ABSTRACT Passarella, M.; De Muro, S.; Ruju, A., and Coco, G., 2018. An assessment of swash excursion predictors using field observations. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 1036–1040. Coconut Creek (Florida), ISSN 0749-0208. Accurate predictions of swash excursion are fundamental for improving the understanding of swash zone dynamics and for coastal management and hazard applications. Researchers have provided several formulas for predicting the swash excursion on sandy beaches. However, the problem of the universality of these formulas is still open. In fact, it is not clear whether the existing formulations are applicable to a wide range of beaches and wave conditions. This study verifies 13 existing swash (total, incident and infragravity) formulations using 13 published experiments (636 swash measurements). The experiments were carried out on beaches worldwide (dissipative intermediate and reflective) under a wide range of wave conditions (including extreme events). Results show that formulas behave differently with under and over prediction. However, some trends can be recognized, which are indeed critical for coastal hazards and management applications: generally, for large swash events (swash >1.5 m) large scatter are found for all formulas. During extreme conditions (swash>2.5 m) total and incident swash are strongly underestimated, while infragravity swash varies for each formula. The maximum errors and the root mean square errors can exceed 2.5 m and 1 m, respectively. [ABSTRACT FROM AUTHOR]

ABSTRACT Jin, C.; Gong, Z.; Geng, L.; Zhao, K.; Xu, B.B., and Coco. G., 2018. Subsurface processes in salt marsh of central Jiangsu coast(China). In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 296–300. Coconut Creek (Florida), ISSN 0749-0208. Studies of tidal flats morphodynamics tend to ignore subsurface processes like bioturbation or underground water dynamics so that changes in the surface elevation are always considered to be the result of sedimentation/erosion on the soil surface. However, at times, subsurface variations can be as large as elevation changes driven by sedimentation and so control the evolution trend of surface elevation. In this study, four observation sites were set up on the salt marsh in the central Jiangsu coast (China). A three-year field observation campaign has been carried out studying seabed elevation changes. The Surface Elevation Table-Marker Horizon (SET-MH) technique was applied to measure surface elevation and net sedimentation. The subsurface variation was derived from the difference between the surface elevation and the sedimentation. Results show that the changes in surface elevation are not equal to the sedimentation and that subsurface process, responsible for such deviation, are strongly affected by storm surge. Storm surges increase the underground water content leading to the observed expansion of the subsurface soil. The expansion results in the rapid increase of surface elevation and it takes almost one year to recover to the surface elevation before the storm season. [ABSTRACT FROM AUTHOR]

ABSTRACT Zhou, Z.; Chen, L.Y.; Townend, I.; Coco, G.; Friedrichs, C., and Zhang C.K., 2018. Revisiting the relationship between tidal asymmetry and basin morphology: A comparison between 1D and 2D models. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 151–155. Coconut Creek (Florida), ISSN 0749-0208. Tidal basin morphology is strongly dependent on the condition of tidal asymmetry which may result in either net import (flood-dominance) or export (ebb-dominance) of sediment. Based on the one-dimensional (1D) shallow water equations, various stability relationships have been developed linking tidal parameters with basin geometry. This study revisits the widely used numerical stability relationship developed by Friedrichs and Aubrey (1988), using a 2D depth-averaged model which is able to describe a more extensive flow field and more realistic bathymetries. Model comparison between 1D and 2D models indicates that excluding or including intertidal areas as a momentum-conveying component can highly affect the tidal velocity distribution and magnitude, particularly when the relative water depth is large (i.e., the ratio between tidal amplitude and mean water depth is small). Meanwhile, the tidal distortion parameters (relative tidal phase 2M2-M4 and tidal amplitude ratio M4/M2) derived from the 2D model appear to be more strongly controlled by the relative water depth (a/h) than that in the 1D model. Further research can be devoted to developing more generic stability relationships which can be applied in a more quantitative manner. [ABSTRACT FROM AUTHOR]

Time-frequency techniques to characterize cuspate patterns in light detection and ranging (lidar) data are introduced using examples from the Atlantic coast of Florida, United States. These techniques permit the efficient study of beach face landforms over many kilometers of coastline at multiple spatial scales. From a lidar image, a beach-parallel spatial series is generated. Here, this series is the shore-normal position of a specific elevation (contour line). Well-established time-frequency analysis techniques, wavelet transforms, and S-Transforms, are then applied to the spatial series. These methods yield results entirely compatible with the traditional method of estimating the spacing of cuspate features. In addition, confidence intervals are readily established for the spatial extent and wavelengths of cuspate landforms simultaneously at multiple scales. Examples show this method is useful for capturing transitions in cuspate shapes. With the advent of land-based time-lapse lidar, such techniques should be particularly useful for characterizing the evolution of cuspate landforms and testing models for beach face dynamics. [ABSTRACT FROM AUTHOR]

Passarella, M.; Ruju, A.; De Muro, S., and Coco, G., 2020. Horizontal runup and seagrass beach cast-litters: Modelling and observations. In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 143-147. Coconut Creek (Florida), ISSN 0749-0208. We collected measurements of wave-driven swash on a beach characterized by the presence and accumulation of seagrass beach-cast litter (the so-called banquette). Beach surveys showed that this deposit can drastically steepen the foreshore thus affecting wave dynamics. This work explores the relationship between vertical and horizontal swash time series, in a previously unreported case of seagrass wrack deposits under mild to moderate incoming waves. The results from the field measurements, obtained by video imagery time stack analysis, show that the seagrass deposits influence wave runup. The horizontal runup extent can be reduced when compared with a nearby "seagrassfree" profile under the same incoming waves. The horizontal runup in case of seagrass presence seems to be approximately one-third of the seagrass absence case. The ratio between observed vertical and horizontal swash, when seagrass deposits are present, is almost 3.5 times the seagrassfree case. The SWASH model was used to extend the analysis beyond our field observations. A number of possible wave forcing scenarios were run on both the seagrass-rich and the seagrass-free profiles. Differences between the cases of seagrass presence and absence show that the horizontal wave runup in case of seagrass deposition can be largely reduced. Using observations and modelling, we show that the seagrass deposits on the beach face and berm inhibit the horizontal runup and so affect one of the key components necessary to predict coastal inundation and to manage coastal areas especially considering ongoing changes in the mean sea level. [ABSTRACT FROM AUTHOR]