2005 Salt Lake City Annual Meeting (October 16–19, 2005)

Paper No. 5
Presentation Time: 3:15 PM


HIGMAN, Bretwood M., Earth and Space Sciences, University of Washington, 310 Condon Hall, Box 351310, Seattle, WA 98195, LYNETT, Patrick, Civil Engineering, Texas A&M, WERC 235-C, 136 TAMU, College Station, TX 77843, MCADOO, Brian, Geology and Geography, Vassar College, Box 735, Poughkeepsie, NY 12604, BORRERO, Jose, Civil Engineering, University of Southern California, Los Angeles, CA 90089 and RUGGIERO, Peter, U.S. Geol Survey, 345 Middlefield Road, MS999, Menlo Park, CA 94025, hig314@u.washington.edu

The 26 December 2004 tsunami resculpted coastal lowlands along hundreds of kilometers of the Sumatra coast. Remote sensing and field survey data shows sediment excavated to a depth of several meters, and then deposited as a sheet with a thickness of tens of centimeters. Eyewitness videos and photos provide a direct look at the violent flows that scoured the landscape. These data provide unprecedented opportunities to describe both how tsunamis impacted coastal geomorphology, and how the tsunami was directed by coastal landforms. Our observations, which include field work in January and April of 2005, focus on the geomorphic effects of the 2004 tsunami.

One-meter resolution Quickbird images taken before and after the tsunami show areas of erosion and deposition up to several hundreds of meters across. The spatial patterns of erosion and deposition likely reflect topographic control of the tsunami's inflow and outflow. We will compare these observations with a 3D, depth integrated tsunami inundation model.

In areas of extensive inundation, the tsunami typically stripped most of the plants in its path. Where the resulting bare ground is evident on satellite photos, a minimum extent of inundation can be mapped onto a digital elevation model from spaceborne thermal emission and reflection radiometry (ASTER). This inundation map can then be related to the height of the tsunami and the slope of the terrain.

Eyewitness videos also provide constraints on the tsunami flows that altered nearshore landscapes. Flow speed was estimated by timing debris in the tsunami front as they moved between points surveyed after the tsunami. The estimated velocities increase from a few meters a second to over ten meters per second as the wave front passes.

The process of analyzing satellite data, eyewitness video and photography from the 2004 tsunami has just begun. This sort of analysis presents unprecedented opportunities in coastal geomorphology, modeling, civil engineering, sedimentary geology, and hazards analysis.