Abstract
Habitat value for benthic organisms has been deteriorated significantly in many riverine estuaries in Japan. One of the most responsible factors for this seems to be the change of river topography, which has been led by the bottom sediment excavation, dredging and other riverworks. Typical topographical change shows deepened river channel and such change has induced enhanced seawater intrusion upstream and shift of bed material to finer grain. Kikuchi River which flows into Ariake Bay has experienced riverbed degradation in recent 50years. This has caused a significant decrease of the yield of a bivalve species, Corbicura japonica. We have pursued numerical simulation, analyzing the salinity and juvenile distribution, to estimate the habitat value for them among different river channel topography. Present channel which has been deepened from the past was estimated to have lower value and restoration plan in which riverbed is raised by 1m was estimated to provide good functional restoration.
