Many people tend to use the boats in the river to take a pleasure. It leads to a ploblem that a boat-generated wave due to the passage of boats causes serious bank erosion. But, march reeds near the bank reduces the energy of boat-ge nerated waves attacking the bank. At the Ara river, we measured the boatwave and its transformation at the front and inside of reeds near the bank and investigete energy dissipation and reflection of the waves due to reeds. It becomes clear th at the reeds are very useful to reduce the waves against the bank and mitigate the bank erosion.