Estimation of seasonal topographic variation in tidal flats using waterline method: A case study in Gomso and Hampyeong Bay, South Korea

Morphologic and topographic changes of tidal flats can be key indicators for monitoring environmental changes and sea level rise. Recently, a number of studies have been performed to estimate temporal topographic changes in tidal flats based on the waterline method using a number of remote sensing data that were acquired at different tidal heights. However, the effect of seasonal variation has not been taken into consideration, nor been understood so far. In this study, 18 scenes of Landsat TM and ETM+ data, covering the period 2003-2004, and corresponding tidal gauge observation data, were used to estimate seasonal topographic variations in two major tidal flats in Gomso and Hampyeong Bay in the southern part of the west sea of South Korea, using the waterline method. Our results showed that the summer deposition was dominant in Gomso Bay with overall average seasonal topographic increase of approximately 18.6 cm. In contrast, Hampyeong Bay showed more dominant summer erosion with overall average seasonal topographic subsidence of about 5.0 cm. In addition; the net overall sedimentation budget was estimated as 6,308,047 m(3) and -2,210,986 m(3) in Gomso and Hampyeong Bay, respectively. The results also indicates that although both bays of Gomso and Hampyeong are classified as semi enclosed tidal flat, the sedimentary fades caused by formation geometry and sediment type led to different topographic changes. The results demonstrate that the amount of seasonal topographic variations is not negligible and are expected to improve the accuracy of topographic change derived by the waterline method. (C) 2016 The Authors. Published by Elsevier Ltd.