Influences of Large-Scale Flood on Water Quality of Tokyo Bay

Abstract

To clarify influences of large-scale floods on water quality of Tokyo Bay, we performed field measurements on pollutant loads under flood conditions, evaluated the long-term trends of SS, organic materials, and nutrient fluxes, and investigated its relation with DO and nutrients in Tokyo Bay. The large flood event caused by the attack of typhoon no. 0709 was observed to have significantly huge environmental impacts on Tokyo Bay. The comparison between the pollutant loads and DO in Tokyo Bay indicates that subsurface hypoxia at the head of the bay was developed after large flood conditions mainly due to decomposition of organic materials appreciably transported through influent rivers. It is also found that the large flood events influenced the nutrients in the benthic layer.