Kangnan Coast has suffered from beach erosion since the extension of breakwaters and two groins of Hsinchu Fishing Harbor was completed. This is a typical example of human impact on coastal erosion in Taiwan. The aim of this article is to explore the erosion at Kangnan Coast using several analyses, such as shoreline revolution detected from satellite images, planform description of depth variation, volumetric change of bathymetry, and variations in the trends of volumetric changes of the sea bottom. Beach erosion at Kangnan Coast in response to structural effects was quantitatively determined. A suggested countermeasure using submerged detached breakwaters, developed through a 3-year study, is proposed to mitigate beach erosion.