Search

Wave runup is one of the most critical parameters contributing to coastline flooding and shoreline change. Many formulas have been developed to empirically predict wave runup characteristics. However, large errors are still associated to these estimates, feeding a debate on the best approach to describe runup through simple parameterizations. In this work we present a comprehensive review on runup, setup and swash empirical models. We use a large database of field measurements to verify the predictive capability of recent formulas, addressing possible sources of variability. We identify the effect of the nearshore bathymetry as an important factor missing in empirical predictors and examine this issue through an analysis of runup simulated with the SWASH model over different barred and linear bathymetries. The details of the submerged beach profile affect estimates, especially with respect to setup values. The lack of standardization in measuring, post-processing and sharing runup data, limits the application of previous published databases on new analysis. We list a set of recommendations that can be used as guidelines for new measurements to broaden the applicability of the datasets in future studies. Finally, we discuss the remaining questions that still need to be further explored. [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]

Abstract: Alongshore variability in swash motions – shoreline oscillations about the mean water level on the beach face – were investigated using video images and a high-resolution morphology survey on an intermediate beach. Under mild, swell-dominated offshore wave conditions, alongshore variation of up to 78% in significant runup height Rs (defined as 4 times the standard deviation of the swash time series) was observed. This variation was predominantly driven by energy at the incident (>0.05Hz) frequencies (where most of the swash energy was observed), and, consistent with previous observations, was mainly controlled by changes in the slope of the beach face (measured at the mean swash location). However, alongshore patterning in wave breaking over the sandbar caused variation in the degree of wave dissipation along the beach and also resulted in alongshore changes to swash motions. Although alongshore changes in beach slope and wave breaking patterning over the bar were observed to be typically correlated, both were needed in a regression model to provide the best explaination of alongshore changes in Rs. At infragravity frequencies (<0.05Hz), alongshore variability was not well associated either with changes in beach slope or wave breaking patterning. Low-mode edge waves were observed in the swash measurements and their contribution to the total energy spectrum was greatest near the location where a shoal was observed, suggesting this shoal may play a role in forcing. The edge waves may have contributed to the swash variability observed at infragravity frequencies. However, in these reflective conditions, the infragravity band plays a secondary role in controlling alongshore variations to swash motions. [Copyright &y& Elsevier]