The 26 December 2004 Indian Ocean Tsunami: Initial Findings from Sumatra

Coastal Response

The Sumatra coast underwent significant modification by the tsunami. The shoreline eroded, beach sand was carried inland, and the coastal plain was flooded. Compared to the erosion and deposition of sediment by the tsunami that occurred relatively quickly, within hours of the initial tsunami impact, coastal subsidence resulted in additional erosion and shoreline retreat during the weeks and months following the tsunami. In addition, beaches started rebuilding as soon as a few weeks after the tsunami, probably adding sand from nearby offshore. These reformed beaches were migrating landward through overwash processes. Some beaches were still migrating landward, impacting roads and redevelopment plans for coastal villages. Future shoreline retreat may continue to impact redevelopment in some areas.

Erosion of beach sand is evident in this before-and-after pair of satellite images of the coast at Lampuuk. White structure near the center of the images is a mosque that survived the tsunami. Satellite image acquired using Space Imaging's IKONOS satellite and processed by the Centre for Remote Imaging, Sensing and Processing (CRISP), National University of Singapore. [larger version]	photo showing new beach sand forming along Sumatra's west coast [larger version]
photo showing new beach forming near Lampuuk [larger version]	photo showing new beach sand forming along Sumatra's west coast [larger version]

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