NUMERICAL SIMULATION FOR RIVER BED TOPOGRAPHY USING FREE SOFTWARE AND FACTOR ANALYSIS BASED ON THE LINEAR INSTABILITY INDEX

Abstract

Simulate computation for the bed topography of a selected reach in the Toshibetsu River was conducted by using the free software RIC-Nays to analyze 2 dimensional river bed evolution of alluvial rivers. Results show good agreement with the observed bed topography, in local bed scouring due to channel bend, alternate bar formation and so on. Next,Blondeaux-Seminara's linear index parameters showing meander growth rate and bar growth rate were considered giving sampled data from the RIC-Nays simulate computation, in order to know the effects of bend-instability and bar-instability in the bed-form development process. From the consideration, it was known that (1) typical meander wavelength (around 2000m) in Toshibetsu River is close to the resonance wavelength found in the linear analysis,therefore the bar-instability is steady and the bed is scoured by the effect of bend; (2) alternate bars grow with around 1200m wavelength (600m bar length) in the whole channel reach, however the effect of bend instability work to suppress meandering of channel with this wave length; (3) BS parameters change the values in each local section of the river channel following the time of calculation process.