Abstract

• Bagan - Nyaung Oo area is the most important architectural complex in Myanmar and is situated between 94°45’ 00” E to 95°00’ 00” E and 21°00’ 00” to 21°15’ 00” N. The research aim is to assess whether any subsidence is currently occurring in Bagan- Nyaung Oo area and to identify whether groundwater extraction is the main case. Subsidence is a typical geohazard for low elevated coastal areas and river basin especially when densely populated. It was only recently that the potential for hazard in Bagan – Nyaung Oo area was acknowledged, but the rates and extent of such hazard remain unknown. Bagan – Nyaunng Oo has a large urban extent and is expanding rapidly. Inhabitants and ecosystems in delta and river basin areas are becoming increasingly vulnerable to the effects of subsidence, triggered both by natural causes and anthropogenic causes. The study area covers mostly the alluvial plain beside the Ayeyarwady River and partly the debris and small fan materials derived from Tuywin Taung and Tantkyi Taung hills which are exposed with rocks of Miocene to Oligocene. Bed rocks are mainly represented by rocks of Irrawaddy Formation (Late Miocene to Pliocene), Okhmintaung Formation (Upper Oligocene) and Padaung Formation and Shwezettaw Formation (Lower Oligocene). Mainly the alluvial soils of Quaternary-Recent are deposited on the plain and along the river banks by fluvial action. The areas susceptible to landslides, rock falls, mass movements, and debris flows hazards are demarcated in the Tuywin Taung and Tant kyi Taung that have been encountered with a number of small tension cracks, active and old landslides. Side cutting in both sides of Ayeyarwady River is caused by river bank scouring and rain water resulting into steep slopes. In the rainy season, low lands adjacent to the Ayeyarwady River and the main streams in the area are affected by flood. Bagan – Nyaung Oo area is situated on the bank of Ayeyarwady River. So water-based transformation and rich agricultural soils create an environment that is suitable for rapid economic growth and urbanization along river basin area. The level of human influence throughout this rapid urbanization and excessive groundwater extraction requires detailed examination in order to prevent man-made disasters and irreparable damage being caused to the environment. Subsidence is a key contributing factor to flood risk and extreme weather events and soit needs to be better evaluated, especially in area with large exposed populations. Human-induced land subsidence is mainly caused by excessive groundwater extraction as a result of rapid urbanization or extraction of other resources. The results of land subsidence are an increased vulnerability to flooding, infrastructural failures, aquifer salinization and permanent geological deformation.