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.