Hydrodynamics of Boulder Transport Induced by Extreme Wave Events - Knowledge Generation and Model Development (HYBTEW)
Final Report Abstract
A significant improvement of the understanding of the mechanisms driving the transport of coarse clasts induced by extreme wave events such as tsunami and storm surges, based on theoretical approaches and physical modelling, has been achieved in the framework of the project ‘Hydrodynamics of Boulder Transport Induced by Extreme Wave Events - Knowledge Generation and Model Development (HYBTEW)’. This project represents also a very good example of a multi-disciplinary collaboration on extreme-wave hazard successfully bringing together geologists and coastal engineers. In the first step, the existing theoretical criteriae for the determination of critical wave height/flow velocity required for initiation of clast motion were reviewed, corrected and extended to other scenarios. Their applicability and accuracy in terms of the assumptions made and magnitude of parameters constituting the equations were discussed together with the wave-induced forces involved in the incipient motion. A tool for the prediction of the critical wave height/flow velocity, with embedded option of sensitivity analysis of main parameters and comparison of different existing approaches was developed. In the second step, tsunami-induced transport of coarse clasts was investigated systematically in a framework of small-scale experiments. Detailed characteristics of the clast transport (transport modi, distance, path and time) were analysed as a function of clast properties (shape, size), flow magnitude (flow depth and velocity) and pre-transport submergence conditions (emerged, partially submerged and fully submerged clasts). The clast models constructed for the model tests represent the clast properties reported from field surveys on coarse clast deposit worldwide, summarized in a form of a very detailed written data basis for the purposes of this investigation. The main advantages of these tests over the previous studies were the larger size and volume of the clast models examined, magnitude of the wave forces exerted by tsunami bore/surge and well as incorporation of the effect of bottom roughness on the clast motion. The transport of lighter clast models exhibited unexpectedly random pattern, indicating the need for a high number of repetition tests to achieve plausible results. An effort was made to employ a new measuring technique for tracking the motion of the clast models in the experiments by means of inertia sensor embedded into the clast model. However, due to large inaccuracies of the measurements that are revealed in the data analysis, its application to this problem still has to be improved.
Publications
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(2015): Experimental study on bore-induced transport of boulder models. Book of Abstracts, 4th International Tsunami Field Symposium, Phuket, Thailand
Freund N.; Strusińska-Correia, A.; Oumeraci, H.
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(2015): Role of coarse clast deposit in reconstruction of past extreme wave events – a summary of recent development and future challenges. Book of Abstracts, 4th International Tsunami Field Symposium, Phuket, Thailand, 46-56
Strusińska-Correia, A.; Oumeraci, H.; Kelletat, D.; Scheffers, A.; Paris, R.
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(2017): Transport characteristics of coarse clasts under tsunami-bore conditions based on large-scale model experiments. Proceedings of the 5th International Tsunami Field Symposium, Lisbon, Portugal, 2 pp.
Strusińska-Correia, A.; Oumeraci, H.; Hermann, E.; Freund N.; Martins A. K.
