Morphology and dynamic sedimentology in front of the retreating Tsengwen Delta, southwestern Taiwan

Abstract

The Tsengwen Delta exhibits subsidence, erosion and retreat of shorelines. The once river-dominated irregularly protruded delta has evolved into a wave-dominated cuspate one with smooth gently curving shorelines. Subprofiler/sidescan sonar data, precision depth echo-sounding and 150 grab samples are integrated to reveal the bathymetry, bedforms, sediment distribution and their governing processes in front of the retreating Tsengwen Delta. Different bathymetry, bedforms, and sediment distribution patterns are found north and south of the offshore of the delta. These discrepancies reflect different interactions of the river influx, topography, and hydrodynamics, resulting in different stages of delta abandonment and subsidence. The spatial sediment distributions not only indicate the future evolution of this destructive delta but also help us to recognize and constrain the interpretation of ancient delta sequences.