Vulnerability Analysis of Episodic Beach Erosion by Applying Storm Wave Scenarios to a Shoreline Response Model

Abstract

Recently, because of the influence of climate change on sea level change, there has been growing concern regarding the erosion of beaches, which play a role in reducing the damage caused by coastal disasters. However, despite these concerns, a comprehensive understanding of the morphodynamic relationship between hazard factors and beach erosion is still lacking. Therefore, in this study, a vulnerability analysis of beach erosion was conducted by applying the shoreline response model (SLRM) of bulk model type, which identifies the physical characteristics of relevant coefficients based on the suspended sediment movement processes. To characterize wave energy incidence, storm wave scenario modeling and extreme wave analysis were conducted using wave data of 40 years on the east coast of Korea provided by the National Oceanic and Atmospheric Administration. A dimensionless mathematical function representing the storm wave scenario was proposed as a function of the peak wave height. In addition, to examine whether the beach vulnerability curve (BVC) obtained from the SLRM is valid, it was compared with the long-term shoreline observation data conducted at Maengbang Beach. For the past 9 years, sand sampling and shoreline observations were performed at Maengbang Beach about 5 times a year. However, since observations were performed in time intervals of several months, the direct comparison with model results was impossible, so a comparative analysis through statistical analysis of shoreline variability was performed. The variability of the shoreline for each reference point followed a normal distribution with a standard deviation of approximately 7.1 m. As a result of comparing the BVC results obtained from these statistical characteristics with those obtained from the model, significant similarity was shown in the high wave condition. Finally, the model was performed on two factors (mean wave height and peak wave height) which appear in SWSF and three factors (wave energy at breaking point, beach response factor and beach recovery factor) which appear in SLRM, and by analyzing the results, an approximate formula for the BVC is derived. This novel BVC approximation equation provides an intuitive understanding of the factors that affect beach vulnerability as well as their importance, and estimates the beach buffer section required to prevent coastal facilities from being damaged by erosion during a specific period. The results of this study can help limit reckless coastal development and mitigate erosion damage.

A Study on the Influence of Sand Median Grain Size on the Short-Term Recovery Process of Shorelines

“…Lesht (1989) reported that the beach recovery factor was proportional to the settling velocity, median grain size, and transport coefficient, and was inversely proportional to the closure depth by applying the cross-shore sediment transport equation proposed by Hanson and Larson (2000). Kim et al (2021) verified the beach recovery factor correlates with the elapsed time from peak wave height to peak erosion by applying storm wave scenario to ODE (ordinary differential equation) model results. Recently, Lim et al (2022) presented research results that clarified the specific physical meaning of the beach recovery factor by introducing the concept of the horizontal behavior of suspended sediment.…”

“…Recently, Kim et al (2021) proposed a bulk response model of the shoreline by the horizontal behavior of suspended sediment. The governing equation of their proposed model showed the type of ODE type similar to that of the shoreline response model proposed by Miller and Dean (2004).…”

“…In various fields such as beach nourishment (Dean, 1991), beach management (Park et al, 2019), and sea-level rise (Bruun, 1962;Dubois, 1990), it has become a means to obtain various engineering solutions to predict and solve catastrophic problems caused by coastal erosion. Recently, Kim et al (2021) expressed the vulnerability of ultimate erosion in terms of sand grain size by applying the equilibrium beach profile equation of Dean (1977). In addition, the empirical formula derived in this way was compared with the correlation between wave energy and shoreline obtained by Yates et al (2009) for 5 years of field observation, and the validity of its application was verified.…”

“…Interpretation of the process of beach recovery is a research theme that is as essential as the process of erosion. Numerous bulk response models have been developed to investigate a shoreline retreat and recovery (Wright et al, 1985;Miller and Dean, 2004;Yates et al, 2009;Kim et al, 2021). Bulk response models introduce functions or coefficients that affect shoreline retreat and recovery.…”

“…Recently, Kim et al (2021) expressed the peak erosion width due to storm waves as a function of beach response and recovery factors by applying shoreline survey data and ODE model results. In addition, Kim et al (2021) and Lim et al (2021) verified that the shoreline survey data collected for many years follows a Gaussian distribution. Moreover, a method for statistically estimating the peak erosion width due to storm waves is proposed.…”