RELATIONSHIP BETWEEN TOPOGRAPHY AND HYDRODYNAMICS AROUND THE TENRYU RIVER MOUTH

Abstract

 To clarify the relationship between topography and hydrodynamics, which is helpful for river mouth management, we analysed the topography data from 2006 to 2014 and wave, water level data from 2002 to 2014 around Tenryu river mouth. The wave transmission rate marks 1 % when the river mouth width is around 50 m and 3 % when it is over 300 m. And the topography and hydrodynamics data shows that the watee level rises . The average water level at river mouth rises up 0.1~0.2 m when the cross-section area closes under 500 m². This shows the average water level can be changed when a small flood in 2008 digged the river mouth without flushing sand bar. the high tide level at Kaketsuka (3.3 km upper from river mouth) shows the wave setup can be seen at high water. The rate of set up is a little less than 10 % of wave height at offshore comparing water level at Kaketsuka and that of river mouth.