Large lagoon port areas are often connected to seas through narrow but long canal channels，and canals are confronted with multiple influences brought by offshore waves，ebb and flow of tides，and ship navigation. The significant wave-current coupling effect and the erosion caused by the ship propeller jet put forward high requirements for the bottom protection of canal bank slopes. In order to solve the bottom protection problem under this kind of complex hydraulic environment，this paper studies relevant calculation theories in the international standards and proposes a suitable calculation method，which can help engineers make better use of international standards to solve related issues. At the same time，the paper can provide a reference for revising Chinese norms and help them to be in line with international standards.