LONG-TERM MONITORING ON THE SAND SPIT MORPHODYNAMICS AT THE TENRYU RIVER MOUTH

Abstract

In this study, long-term monitoring on the sand spit morphodynamics at the Tenryu River mouth was carried out based on the time series of sand spit profiles extracted from the field camera recorded images between Apr 2007 and Dec 2009. Time stack images were applied to qualitatively characterize the variation of sand spit morphology at the representative longshore location. Primarily analyses were conducted by focusing on the bulk statistical properties of the recorded sand spit profile data. Detailed insight into the evolution process of the sand spit shoreline location was estimated through the Empirical Orthogonal Function (EOF) analysis. Sand spit riverside morphodynamics presents a short-term, but intensive variation pattern and is found to be closely related to the overtopping or flood events. Modification on the sand spit shoreline location shows an asymmetric nearshore process. In the first two years, slow beach accretion accompanying with the eastward longshore sand movement prevailed; whereas, rapid shoreline erosion, together with the westward longshore sand movement, became predominant in the following half year.