NATURAL HAZARD ASSESSMENT OF SW MYANMAR - A CONTRIBUTION OF REMOTE SENSING AND GIS METHODS TO THE DETECTION OF AREAS VULNERABLE TO EARTHQUAKES AND TSUNAMI / CYCLONE FLOODING

NATURAL HAZARD ASSESSMENT OF SW MYANMAR A CONTRIBUTION OF REMOTE SENSING AND GIS METHODS TO THE DETECTION OF AREAS VULNERABLE TO EARTHQUAKES AND TSUNAMI / CYCLONE FLOODING Barbara Theilen-Willige Berlin University of Technology (TU Berlin), Institute of Applied Geosciences Email: George Pararas-Carayannis Tsunami Society, Honolulu, Hawaii, USA Email: ABSTRACT Myanmar, formerly Burma, is vulnerable to several natural hazards, such as earthquakes, cyclones, floods, tsunamis and landslides. The present study focuses on geomorphologic and geologic investigations of the south-western region of the country, based on satellite data (Shuttle Radar Topography Mission-SRTM, MODIS and LANDSAT). The main objective is to detect areas vulnerable to inundation by tsunami waves and cyclone surges. Since the region is also vulnerable to earthquake hazards, it is also important to identify seismotectonic patterns, the location of major active faults, and local site conditions that may enhance ground motions and earthquake intensities. As illustrated by this study, linear, topographic features related to subsurface tectonic features become clearly visible on SRTM-derived morphometric maps and on LANDSAT imagery. The GIS integrated evaluation of LANDSAT and SRTM data helps identify areas most susceptible to flooding and inundation by tsunamis and storm surges. Additionally, land elevation maps help identify sites greater than 10 m in elevation height, that would be suitable for the building of protective tsunami/cyclone shelters. Science of Tsunami Hazards, Vol. 28, No. 2, page 108 (2009) 1. INTRODUCTION The south-western region of Myanmar is vulnerable to numerous natural hazards, such as earthquakes, cyclones, floods, tsunamis and landslides (Fig. 1). The present study was undertaken for the purpose of using remote sensing satellite imagery and methodology to determine Myanmar’s vulnerability to disasters and for ways to mitigate losses of lives and improve on disaster preparedness. The assessments described in subsequent sections are based on satellite data of the Shuttle Radar Topography Mission-SRTM, MODIS and LANDSAT and focus on geomorphologic and geologic investigations of the southwest region of Myanmar. The main objective is to detect areas vulnerable to inundation by tsunamis and cyclone surges, but also to identify seismotectonic patterns, the location of major active faults and local site conditions that may enhance earthquake ground motions and seismic intensities. As illustrated by this study, linear, topographic features related to subsurface tectonic features become clearly visible on SRTM-derived morphometric maps and on LANDSAT imageries. The GIS (GeoInformationSystem) integrated evaluation of LANDSAT and SRTM data helps to identify areas most susceptible to flooding and inundation by tsunamis and storm surges. Land elevation maps help identify sites with elevations greater than 10 m that would be suitable for building protective evacuation shelters. However, before proceeding with the analysis of the satellite data, a brief review of the region’s disaster exposure is appropriate. Fig. 1. The vulnerability of southwest Myanmar to natural hazards. Science of Tsunami Hazards, Vol. 28, No. 2, page 109 (2009) 2. MAYNMAR’S VULNERABILITY TO NATURAL DISASTERS Mynmar’s high vulnerability to natural disasters results from its unique geographic and geologic location and geomoprhology. Myanmar borders the Bay of Bengal to the southwest and the Gulf of Martaban and the Andaman Sea along its southern periphery. The country’s extensive coastline of about 1,930 (1,199 mi) and its extensive lowland areas make it particularly vulnerable to all types of marine and terrestrial disasters. Its geotectonic evolution and proximity to regions of subduction and major antithetical faulting, make it vulnerable to earthquakes, some of which could be potentially tsunamigenic. Cyclones and Cyclone Surges - Myanmar is particularly vulnerable to cyclones originating in the Bay of Bengal during pre- and post-monsoon seasons from April to May and from October to November. These cyclones result in heavy rains, floods and storms surges, especially in the coastal region of Rakhine State. Cyclone-related disasters occur in this region every 3 to 4 years. Additionally to the destruction by high winds, storm surges generated by the cyclones in the region usually flood the low lying and densely populated Ayeyarwady (Irrawaddy) river delta region as well as other coastal regions along the Gulf of Martaban. On May 1-3, 2008, Cyclone Nargis generated in the Bay of Bengal was the deadliest to ever hit the country. It made landfall across the delta of the Irrawaddy River, then continued northeast along the coastline and devastated Myanmar (Fig. 2). Figure 3 shows flooded areas in the Irrawaddy region. Fig. 2. Cyclone Nargis Path over the Irrawaddy River Delta Region (web graphic) Science of Tsunami Hazards, Vol. 28, No. 2, page 110 (2009) Fig. 3. Flooding by Cyclone Nargis surge at the Irrawaddy Delta. Non-flooded land of higher elevation seen as islands from NASA satellite. Maximum reported flooding by Nargis’ surge was at least 4 meters (13 feet). The cities of Yangon, Irrawaddy, Pegu and the states of Karen and Mon Worse were the most severely affected regions (Pararas-Carayannis, 2008). The cyclone was responsible for unprecedented loss of life and destruction. It is estimated that more than 100,000 people lost their lives As illustrated by the May 5 MODIS image, the entire coastal plain was flooded. The image from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite uses a combination of visible and infrared light to make floodwaters visible (Fig.4). Based on data of the RADAR satellites TerraSAR-X (DLR/Infoterra) and ALOS/PALSAR (JAXA), the Center for Satellite Based Crisis Information (ZKI) at DLR produced maps of the affected areas (DLR, ZKI, 2008). Science of Tsunami Hazards, Vol. 28, No. 2, page 111 (2009) Fig. 4. MODIS image from the flooded areas (NASA) Water is blue or nearly black, vegetation is bright green, bare ground is tan, and clouds are white or light blue. The wetlands near the shore are a deep blue green. The colour-coded image above shows the flooded areas in blue-reddish and grey tones. Floods - Four major rivers flowing southward traverse southwest Maynmar. Sometimes, during the heavy monsoon season, rainfall in the north causes the rivers to exceed maximum levels and result in destructive flooding of adjacent towns and villages. The lowland, delta regions are also vulnerable to similar disastrous floods during the monsoon season, particularly when the high tide and the high river water flow occur at the same time. Although earthen dykes have been built to protect the lowlands, there have been times when the dykes have failed and great floods have resulted in great losses of life and property. Fig. 4 and 5 show NASA and Google Earth images of (...truncated)