Estimation of the Suitable Sediment Load for Ayu Fish Habitat in the Kizu River

Abstract

It is necessary to clarify the effect of the change of sediment transportation on environmental condition and maintenance of artificial structure. The environment understanding that agents that change the river bed geomorphology are associated with environmental factors which prescribe the habitat of an organism. Then the purposes are to conduct environmental evaluation based on the suitability for sweet fish habitat in Kizu River, and to estimate two dimensional feature of reproduction habitat used the distribution of piscivorous aquatic birds indirectly, and finally, to estimate the amount of sediment load for creating suitable river bed geomorphology for sweet fish. In order to evaluate river bed geomorphology based on the habitat of sweet fish, to distinguish the suitability of riffles for reproduction habitat and growth habitat because they have different geomorphological characteristics. The most suitable amount of sediment estimated from this approximate curve is 79961 m3/year, and the riffle area of traverse and converge type is 73004 m2. Previous environment evaluation is based on past situation. The suitable river management condition have been estimated from the historical comparison in a river focusing on various geomorphological parameter. However, environmental evaluation method in this study enables to evaluate the assumed conditions and compare with various scenarios and even between rivers.