THE IMPACT OF BRIDGE CONSTRUCTION AND LARGE-SCALE FLOODING ON THE ESTUARY ECOSYSTEM IN THE TAMA RIVER ESTUARY

Abstract

 The purpose of this study was to clarify physical and ecological impacts of the dredging work associated with constructing bridge piers, and those by a large-scale flooding event in the Tama River estuary. Based on the results of periodic environmental surveys conducted for about four years, we analyzed the effects of dredging work and the largest flood in the past on the topography and ecosystem of the tidal flat. As a result, it was inferred that the sediment environment and benthic communities of the tidal flat were not greatly affected by the dredging work. Whereas, remarkable topographical and sediment environmental changes were observed due to the largest flood in history. Benthic communities, mainly composed of opportunistic species, appeared immediately after the flooding, which indicate that the population of organisms would recover relatively quickly against large-scale physical disturbances. However, long-term investigations are required to determine whether the same communities as before the flood, in which large, long-lived benthic organisms such as bivalves appeared stably, could be formed.