INFLUENCE OF VEGETATION IN TRIBUTARIES OF THE ARAKAWA MIDDLE BASIN ON FLOOD FLOW AND EVALUATION OF ECOLOGICAL FUNCTION

Abstract

Resistance by plant growth is increasing at the tributaries of the middle Arakawa basin. This study performed flood flow observation, numerical simulation, and GIS data analysis for the appropriate management of river vegetation. The water level hydrographs of Typhoon Hagibis in the Toki-gawa River and Oppe-gawa River were observed by newly set pressure gauges considering river and vegetation characteristics. Observed data clarified the change of the water level profile during the rising and decreasing period. In addition, the backwater rise by the river vegetation was numerically estimated. The factors which affect the local water level were evaluated. Finally, the river habitat was classified in relation to the flood influences and the living organisms in each classified habitat were analyzed using GIS data. This analysis clarified the points to keep in mind for the management of the river vegetation.