Technical Studies

The purpose of this study is to examine the influence of migration process of main channel along the sand/rock bed river on channel stability, through the understanding on the sediment transport mechanism along the channel with compound cross section by means of characteristics analysis and field investigation. The outcome from the theoretical analysis and ap-plication study is expected to be able to provide the engineers as a guide-line for their design and planning needs.

From the quantitative characteristics analyses of sand/rock bed river morphology of main channel in Jhuoshuei river and Bajhang river, one can find that vertical scours plays the major role to affect the channel stability although the lateral variation of cross section may not be ignored. To further quantify the complex migration behavior of the sand/rock bed channel, no efficient other than the numerical model can be used for the planning purposes. However, as know so far, no suitable model has been developed yet for the sand/rock bed channel migration behavior. This study will extend the RESED2D model, which is a 2D depth-averaged mobile-bed model, to couple with capabilities of simulation of bed-evolution and river bank erosion/sliding. The two mechanisms including sand/rock bed evolution and river bank (sand material) sliding are couply computed and applied to specific reach with sand-material bed in Jhuoshuei River.

For the present study, the rock erosion mechanism will be tentatively embeded in RESED2D model, and applied to certain reach of Jhuoshuei River. The simulation results were compared with the data observed from the field before and after typhoons event. Finally, the application study on Jhuoshuei River draws out some valuable information for future engineer-ing improvement measures planned.

99I031(99.6.29~99.12.15)