Tsunami inundation modelling based on detailed roughness maps of densely populated areas

Abstract

Abstract. An important part within the German-Indonesian Tsunami Early Warning System (GITEWS) project was the detailed numerical investigation of the impact of tsunamis in densely populated coastal areas of Indonesia. This work, carried out by the German Research Centre Geesthacht (GKSS), in co-operation with DHI-WASY, also provides the basis for the preparation of high resolution hazard and risk maps by the German Aerospace Center (DLR).In this paper a method is described of how to prepare very detailed roughness maps for scenario computations performed with the MIKE 21 Flow Model FM in three highly resolved (∼10 m) priority regions, namely Kuta (Bali), Padang (West-Sumatra), and Cilacap (southern coast of Java). Roughness values are assigned to 43 land use classes, e.g. different types of buildings, rural and urban subareas, by using equivalent coefficients found in literature or by performing numerical experiments.Comparisons of simulations using differentiated roughness maps with simulations using constant values (a widely used approach) are presented and it is demonstrated that roughness takes considerable influence on run-up and inundation.Out of all simulations, the results of the worst case scenarios for each of the three priority areas are discussed. Earthquakes with magnitudes of M W =8.5 or higher lead to considerable inundation in all study sites. A spatially distinguished consideration of roughness has been found to be necessary for detailed modelling onshore.

Modeling propagation and inundation of the 11 March 2011 Tohoku tsunami

“…Different friction coefficients were tested in ComMIT to account for wave attenuation caused by land cover roughness such as forests or human-made structures, which are supposed to influence inundation characteristics (Gayer et al, 2010;Mimura et al, 2011a). From the Manning coefficients n 2 = 0.0009, n 2 = 0.0017, and n 2 = 0.0012, the latter provides the best results when validating the modeled surface elevation against run-up measurements from the field.…”

Postface "The GITEWS Project – results, summary and outlook"

“…In addition a large number of simulations of different tsunami scenarios enabled the run-up modeling group to get a detailed insight into possible hazards during flood events in the selected priority regions Padang, Cilacap, and Kuta which were investigated by Gayer et al (2010).…”

A nested-grid Boussinesq-type approach to modelling dispersive propagation and runup of landslide-generated tsunamis

“…Most existing nested-grid tsunami simulating packages, such as MOST ("Method of Splitting Tsunami") (Titov and González, 1997), TUNAMI-N2 (Imamura, 1996), COMCOT ("Cornell Multi-grid Coupled Tsunami Model") (Liu et al, 1998), and MIKE 21 (Gayer et al, 2010), are based on the shallow water equations which have good applications to seismically generated long waves. In the study by Grilli et al (2010), tsunami propagation and runup are split into two stages, both modelled with FUN-WAVE.…”