An analytical model for beach erosion downdrift of groins: case study of Jeongdongjin Beach, Korea

Abstract

Abstract. Beach erosion at the unprotected downdrift end of a groin is common with waves approaching the structure obliquely. This phenomenon has often occurred on the downdrift side of natural groins on the east coast of South Korea during high waves in winter months. The resulting planform assumes a distinctive crenulate shape with a maximum indentation point landward of the erosion. An analytical model is employed to study the beach erosion at the downdrift end of a natural rock groin at Jeongdongjin Beach in Korea, using mathematical equations derived from the parabolic model for headland-bay beaches in static equilibrium, to predict the downdrift control point and maximum indentation of the eroded shoreline. These equations are solved using the prevailing wave height, wave angle at breaking and wave direction derived from analyzing NOAA's wave data over 40 years and the longshore sediment transport rate calculated from the wave data. The location of the calculated maximum indentation is also verified using shoreline video monitoring data and compared with the result of a one-line numerical model for shoreline change. The limitation of the proposed analytical model is discussed as is the effect of sediment bypassing the groin.

Prediction of Equilibrium Shoreline by Wave Environmental Change Using MeePaSoL Software

“…However, most of natural topographies are in shapes of curvilinear ones therefore the application of PBSE, taking the accounts of natural topographies and artificial structures, needs to be applied. Therefore, Lim, Hwang, and Lee (2022) proposed that the PBSE is applied to the polar coordinates assuming that the initial shoreline would be the fitted circle. The PBSE transformed to the polar coordinate system proposed by Lim, Hwang, and Lee ( 2022) is as follows:…”

“…where, the 𝑟 𝑓 represents the distance from the center of fitting circle to the focus point, 𝐹(𝑟 𝑓 , 0). Using these concepts, Lim, Hwang, and Lee (2022) developed the MeePaSoL software which shows an outstanding performance in the prediction of equilibrium shorelines with respect to the construction of coastal structures (Hsu et al, 2021;Lee, 2015;Lim, Hwang, and Lee, 2022). Figure 6 is an example of applying MeePaSoL software to Sokcho Beach.…”

“…Among them, the wave environment is one of the main factors that immediately affect changes in the shoreline. Jeongdongjin Beach, Korea is a representative example of severe erosion damage caused by seasonal high waves that incidence at an oblique angle (Lim, Hwang, and Lee, 2022;Xia, Lim, and Lee, 2023).…”

Evaluation of beach response due to construction of submerged detached breakwater

“…When the predominant wave direction is 42.2°(the shore normal measured clockwise from North), no LSTR occurs (Figure 3). Incoming waves during winter mostly cause the development of southward LSTR, on the other hand, the sediment gets to be transported to the north when the waves flow in during summer (Lim et al, 2022b). If no long-term shoreline changes are found, it is noted that the total northward and southward LSTR balances out, yielding the net LSTR is zero (0).…”

“…Direction of LSTR according to incident wave direction and shoreline from true north (reproduced from Lim et al, 2022b, licensed CC-BY-4.0).…”