The tsunami and cyclone hazard in Myanmar - Surveying coastal geoarchives for sedimentary evidence of extreme wave events

• Applicant: Dr. Dominik Brill
• Subject Area: Physical Geography
• Term: from 2016 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 299338813

Since at least the 2004 Indian Ocean Tsunami (IOT) the benefits of geological tsunami evidence are well established. Although the IOT 2004 also had an exceptional magnitude, its catastrophic effects can only be explained by missing awareness concerning the tsunami risk of the region. Being the first tsunami of this dimension on instrumental and historical records, only geological evidence could have provided information on predecessor events to raise awareness and trigger vulnerability-reducing measures. This example and similar observations after tropical cyclone (TC) Nargis 2008 in Myanmar or Supertyphoon Haiyan 2013 in the Philippines demonstrate that robust hazard assessment must be based on the occurrence of extreme wave events (EWE) with different magnitudes over a prolonged time. While frequency-magnitude information from modern and historical TCs and tsunamis in SE Asia is restricted to a few centuries, geological imprints potentially cover periods of several millennia and record EWE with exceptional magnitudes and low frequencies.While the IOT 2004 triggered intensive research in most affected areas, still very little is known about EWE deposits in Myanmar. In consequence, the long-term hazard due to exceptional TCs and tsunamis is poorly constrained, although Myanmar is exposed to coastal flooding from three major sources: (i) eastward-moving TCs generated in the Bay of Bengal (e.g. TC Nargis); (ii) tsunamis triggered by complete ruptures of the North-Sumatra-Andaman segment of the Sunda Arc (e.g. the IOT 2004); and (iii) tsunamis triggered by ruptures of the Rakhine (Arakan) segment offshore western Myanmar (e.g. the 1762 tsunami). Since the lack of investigations is at least partly the result of a limited research activity due to the political isolation of Myanmar during the last decades, we assume that geological evidence of EWE is present in suitable near-shore geoarchives; these can contribute to an improved understanding of the long-term tsunami and cyclone hazard.While the preconditions for the proposed research are provided by a cooperation between Yangon and Cologne Universities, the possibility of poorly preserved or scarce EWE deposits advises a survey of several sites rather than a systematic investigation of individual locations. Therefore, 6-8 beach-ridge plains along the coasts of Myanmar shall be surveyed using light equipment for levelling (DGPS) and sampling (trenches, push cores) of EWE landforms (storm ridges, washover fans) and sand sheets. In combination with sedimentological (granulometry, fauna, mineralogy, geochemistry) and chronological (radiocarbon, optically stimulated luminescence) laboratory analyses the proposed survey shall trigger follow-up projects by (i) providing a basis for the systematic investigation of promising sites; and (ii) transferring knowledge to local graduates that participate in the field survey.

• DFG Programme: Research Grants