Estimation of Background Erosion Rate at Janghang Beach due to the Construction of Geum Estuary Tidal Barrier in Korea

Abstract

In this study, a reduction in sediment budget due to the development of a river watershed, resulting in coastal erosion, was reviewed, and the rate of background erosion was calculated through an examination of the loss of coastal sediment into the open sea. The west coast of the Korean peninsula is severely impacted by the intercept of inflowing sediments from rivers, owing to the watershed development. However, the effects have not fully propagated into the entire coastal area, and thus, the long-term coastal erosion remains insignificant. However, a serious and irrevocable disaster may occur once the coastal erosion begins. Therefore, an analysis of the coastal erosion resulting from changes in the sediment budget, due to the development of the watershed, was conducted on Janghang Songrim Beach. A littoral cell of the Geum River was selected for a quantitative analysis of the decrease in the sediment budget from the watershed development. The rate of coastal sediment loss offshore, which reflects the characteristics of the Janghang Songrim Beach, and the future rate of coastal erosion were calculated. Then, the results were verified by employing geometrically corrected satellite photographs from previous years. This will enable us to predict the time of coastal erosion in the future due to a reduction in the sediment budget and watershed development, and prepare for future disasters resulting from the coastal erosion. Based on research into the components constituting the coastal development, the present study presents theoretical formulae allowing the prediction of the sediment budget and providing a practical contribution to the prevention of coastal erosion, for which additional reliable studies need to be conducted.

Quantitative interpretation of risk potential of beach erosion due to coastal zone development

“…It shows the time-dependent change in the beach area by reflecting the effects of the sand loss rate lost to the offshore and the decrease rate α of the sand flowing into the beach, which are variables representing the effects of source and sink. The theoretical solution is as follows (Lee and Lee, 2020).…”

“…This study presents a quantitative method for identifying the ultimate risk to beach erosion due to the anthropogenic development in watershed, coastal waters and lands, omitting climate change and sea-level rise. The sediment budget reduction potential caused by reduction in sediment supply from an upstream river was estimated using a principal of mass conservation (Lee and Lee, 2020). The estimation of longshore sediment deposition potential was evaluated by the deformation of a static bay shape (Hsu and Evans, 1989).…”

“…The sediment budget reduction potential is defined as the reduction in the planar beach area mainly followed by the lack of river sediment load due to the watershed development. Applying the law of conservation of matter to the beach of the littoral cell (Lee and Lee, 2020), it can be expressed as…”

“…A detailed description of the seaward loss of suspended sand due to wave action, , expressed in , is presented in Lee and Lee (2020). If Eq.…”

“…For example, a decrease in sediment discharge due to the construction of dams in rivers (Foley et al, 2017;Warrick et al, 2019) or an increase in sand loss due to sand mining (Edward et al, 2006) causes gradual shoreline retreat. And Lee and Lee (2020) proposed an equation to calculate the beach width according to the law of mass conservation by placing variables representing two main factors about sediment budget.…”