ASSESSING VULNERABILITY OF RIVERBANK REVETMENTS IN A REGIONAL DRAINAGE SYSTEM DURING STORM OR TYPHOON EVENTS

Abstract

In this study, a quasi three-dimensional hydrodynamic model and field measurements were combined to assess the vulnerable segments of the De-Shang Creek drainage system during the 610 flood and Typhoon Kong-Ray. An automatic monitoring system was installed to record channel water levels, and the displacement and pore water pressure variations inside the riverbank revetments. The results show that the variations of water levels and pore water pressure were almost at the same pace, which indicates the drainage system inside the revetments work well. The flow-induced lateral shear stress and safety factor (S.F.) of river embankments from numerical simulations are the two indexes used to assess the vulnerability of the riverbank revetments. By using the 610 flood and Typhoon Kong-Ray as test cases, the combined hydrodynamic and revetment stability model is able to indicate if riverbank revetments are in danger during the storm or typhoon events. In the observational site, the damages of the revetments in the 610 flood may be due to the exceedance of the flow-induced shear stress over the critical resistance shear stress of the revetments. Overall, this study show the combined hydrodynamic and revetment stability model is a useful non-engineering method on assessing stability of riverbank revetments during storm or typhoon events.