Md. Serazul Islam^1,, Tetsuro Tsujimoto²

Small-scale laboratory experiments and same scenario numerical analyses were conducted to understand levee breaching phenomena and subsequent disasters risk in floodplain focusing on the effects of the relative height of river bed to the floodplain and the bed materials. In the present study, the area including river, levee and floodplain has been reproduced in both experiment and numerical simulation because not only the behavior of levee but also the phenomena in river and floodplain are intimately related to one another. As a result the followings have been clarified: Higher bed level brings more rapid propagation of the levee breach and widening with more inundation and sediment deposition on the floodplain. River bed degradation in the upstream of the levee breaching point may cause further risk of breach. While as for the effect of bed materials, it has exposed that the finer materials has higher risk not only by more deposition on the floodplain but also by remarkable river bed degradation.

levee breach, disaster risk, river bed, floodplain, sedimentation