Morphology of intertidal flat is dictated by the input of sediments from rivers and the subsequent redistribution by waves, currents, and gravity-driven flows. An analytical models is develop for dynamic equilibrium profile from Falcini et al (2012) and Yamada et al (2004) equations and numerical simulations are used to predict the long-term cross-shore morphology changes on intertidal flat adjacent of river mouth. By using these models, we explore the gravity flows and sea bottom slope in determining the critical conditions for bypass of gravity-driven sediment transport. The field site of this research is located on the center of the eastern coast of Ariake Bay at river mouth of Shirakawa River, Japan. Monthly bed level measurement from February 2001 to January 2013 with the distance between 100 to 1050 m and the interval of 10 m from seawall was analyzed. Oceanographic data such as tide level, significant wave height, wave period, and wind velocity measured at an observation tower of Kumamoto Port. Water debit of Shirakawa River is obtained from Ministry of Land, Infrastructure and Transport of Japan. Based on model predictions, we found that the dynamic equilibrium profile is spatially and temporally consistent with field observations and it predicted to be deeper and boarder associated with sediment
