PHYSICAL ENVIRONMENTAL CHARACTERISTICS OF THE OTOGO TIDAL FLAT IN THE YOSHII RIVER AND PROPOSAL OF NEW TIDAL FLAT CREATION SITES

Although tidal flats with good natural environment spread on both banksides in the lower reach of Yoshii River, flat area considerably decreased owing to river bank and dam construction works. The Otogo is remaining estuary. This study proposes a candidate site for creation an estuary depending numerical analysis results. First, physical was clarified by examining observed salinity data numerically obtained hydraulic data. Second, promising creating new flat, which has similar that investigated proposed left side 4-4.6 km from mouth, approximately 2 upstream flat. Finally, some experiments were conducted assuming sediment replenishment groynes. results show extracted sustainability against flood flow several years return period.