Abstract: In this paper, a multibeam bathymetric system with wide coverage and high resolution was used to obtain detailed bathymetric data of an underwater marine slope near foundations of Xihoumen Bridge. The system provides the basic topographic data for the further analysis and evaluation of the overall stability of the marine slope by generating underwater topographic map and analyzing characteristics of the seabed topography and geomorphology. Through the establishment of threedimensional point cloud model, the shape, gradient, topographic fluctuation and detailed to pographic features of underwater coastal slope can be determined quickly and intuitively.Through judging whether there are some unfavorable phenomena such as erosion and scour, the stability inspection of underwater marine slope near the bridge foundation could be conducted. The success of the multibeam sounding system application in the inspection of this underwater marine slope near the bridge foundation could be referenced for similar projects in the future.

Key words: Multibeam Sounding System, Xihoumen Bridge, Bridge Foundation, Underwater Marine Slope, Slope Stability Inspection