Annual Variations of Tide Level and Mudflat Profile

Abstract

Mudflat profiles were measured monthly along two cross-shore lines exceeding 1,000 m in the vicinity of a river mouth for 2 years. All the measured profiles are shown to be approximated within average errors of 3 cm by a quadratic profile with three parameters that vary with time. The temporal variations of the quadratic profile represented by the quadratic convexity, mean slope, and vertical displacement are correlated with available data on the tide level and range, significant wave height, wind speed, and river discharge in the vicinity of the field site. The vertical displacement varied in phase with the annual tide level variation of 40 cm, but the mudflat displacement was only 20% of the tide level displacement. The mudflat slope became gentler or steeper as the tide level rose or fell annually. The proposed quadratic profile approach may be useful in examining intertidal mudflat morphology at other sites.