Bedding structures in Indian tsunami deposits that provide clues to the dynamics of tsunami inundation
Published:January 01, 2012
Adam D. Switzer, S. Srinivasalu, N. Thangadurai, V. Ram Mohan, 2012. "Bedding structures in Indian tsunami deposits that provide clues to the dynamics of tsunami inundation", Natural Hazards in the Asia–Pacific Region: Recent Advances and Emerging Concepts, J. P. Terry, J. Goff
Download citation file:
The 2004 Indian Ocean tsunami deposited an extensive sandsheet on the coastal plain of SE India. At particular sites, the sedimentary bedding in the sandsheet provides evidence of variable energy conditions and flow during inundation of the coast. Trenching of the deposits at sites where only unidirectional flow was observed allowed the investigation of changes in hydrodynamics recorded in bedding structures without the added complexity of return flows and reworking. A high-velocity initial surge is recorded as upper flow regime (UFR) plane bedding. Following the initial high flow a period of falling flow velocity and quiescence occurs where sediments settle out of suspension, often resulting in a reverse graded bed that transitions to a graded (fining-up) bed. As water levels begin to decline after maximum inundation sheet flow caused the formation of inversely graded (coarsening-up) beds or a return to UFR conditions. At one site the final stages of tsunami inundation is recorded as small channels that have an erosional base and are filled with graded sediments that exhibit complex patterns of sedimentation. Pits excavated in areas of unidirectional flow allow the development of a sedimentary model for tsunami sediment dynamics across flat topography under unidirectional flow conditions.
Figures & Tables
Natural Hazards in the Asia–Pacific Region: Recent Advances and Emerging Concepts
Even a cursory glance at any map of the Asia–Pacific region makes a striking impression: in addition to the large continental landmass the region encompasses a truly vast expanse of ocean, dispersed over which are thousands of islands. Many might say that it could not be a worse time to live in this region. In the past few years we have experienced not only a number of devastating tsunamis (Indonesia, Solomon Islands, Samoa, Japan), but should not forget either the seemingly endless list of other natural hazards such as tropical cyclones and typhoons, volcanic eruptions, river floods and wildfires, amongst numerous others. This Special Publication represents an important collection of both conceptual and first-hand field investigations across the Asia–Pacific region. By highlighting some of the recent advances and emerging ideas in natural hazards research, the volume draws together these disparate lines of evidence into a clear regional focus.