Abstract: In the past few years， flexible beach protection materials like soft mattress have been widely used in hydraulic and channel regulation projects in the Yangtze River estuary， and local scour holes are associated with the implementation of this kind of projects. In order to summarize and analyze such problems, the Yangtze River estuary′s deepwater channel regulation project and its extension projects are taken as the case studies， and the real morphological shape along with soft mattress projects in the Yangtze River estuary is collected. According to the hydrodynamic causes， the local scour holes are classified as scour hole around soft mattress， scour hole caused by flow around and scour hole caused by drop flow， and the features and evolution processes of different scour holes have been studied in this study.