Run-up related to onshore tsunami flows

Abstract

The focus of the thesis is on onshore tsunami flows with special attention on tsunami runup. In the aftermath of a tsunami, the most evident clue on the extent of a run-up is the water marks left behind. The trim-line recorded by surveyors is one of the most valuable pieces of information needed to determine the hydrodynamics parameters of the tsunami.However, it is also known that the most commonly used 2-D hydrodynamic models that attempt to reproduce the tsunami event do not produce good results during the onshore propagation phase. To bridge this gap, the use of an amplification factor proposed by Satake ( 1994) is investigated in this study. Experimentally, we used solitary waves to impinge on a model scaled coastal cliff to examine the flow depth at different onshore locations. The measured data are compared with the numerical results using the Delft3D-FLOW model.Besides, we also used dam break waves to evaluate the run-up both experimentally and numerically. The reason for doing so was two folds. First, dam break waves can provide us with a comparison to the often used solitary waves. Second, due to the discovery of a cave that has well preserved tsunami deposits off the coast of Banda Aceh, Indonesia, we found that experimental dam break waves have the potential not only to bring the sediments in, but also allow ample time for deposition to occur. Numerically, the sedimentation time within the cave is not easy to obtain using 2-D numerical models. Hence, based on the trimline time series recorded, we provided a hypothetical sedimentation time that can be obtained using non-sediment laden flow tests.