A barrier island works as a buffer zone against wave and tidal forces, especially in river estuaries. To quantitatively analyze the buffer zone mechanism, understanding the wave, tide precipitation and groundwater-table by using long-term field observation is necessary. This study presents a coastal buffer zone mechanism in a barrier island (Jinudo) of the Nakdong river estuary in Busan, South Korea. For the establish coastal buffer zone in barrier island, we measured the groundwater at five observation points for 26 months from March 2012 and obtained wave and tidal data from a national observation station near the river mouth. We constructed a wave transformation numerical model and extracted breaking wave conditions, and then we compared data from the numerical model with a real-time groundwater data. According to the result, the buffer zone maximized up to 166.3 m from the shoreline with a wave height and period of 0.05 m and 12 sec, respectively, for 8 hours. Considering seawater infiltration, the buffer zone was observed to reduce to 125.0 m. The critical values are likely to define a coastal protection zone and vegetation distribution characteristic.
Estuary barrier Island; groundwater; salinity; long wave; coastal buffer zone