HYPORHEIC FLOW CAUSED BY BAR MORPHOLOGY ON CHUM SALMON SPAWNING AREA IN MIDDLE REACH OF TOYOHIRA RIVER

Abstract

To understand relationship among bar morphology, hyporheic flow and chum salmon spawning environment, the cross sectional profile, river water and ground water level distribution around bar and hypoheic flow were surveyed. Numeric calculation was also conducted to understand hyporheic flow path. The results revealed that a river water elevation gap between bar crest and front, generates welling out hyporheic flow around bar front. Numeric calculation also revealed flow path of hyporheic flow which sink into river bed on the bar crest and well out on the bar front. Spawning redds were found around bar front where hyporheic flow well out. Thereby, we conclude that bar morphology contribute generating suit hypoheic flow for spawning environment on bar front.