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When referring to this work, full bibliographic details including the author, title, awarding institution and date of the thesis must be given e.g. AUTHOR (year of submission) "Full thesis title", University of Southampton, name of the University School or Department, PhD Thesis, pagination http://eprints.soton.ac.uk UNIVERSITY OF SOUTHAMPTON FACULTY OF SOCIAL AND HUMAN SCIENCES Geography and Environment Academic Unit Climate Change and Landslide Risk Assessment in Thailand by Shotiros Protong Thesis for the degree of Doctor of Philosophy July 2016 UNIVERSITY OF SOUTHAMPTON ABSTRACT FACULTY OF SOCIAL AND HUMAN SCIENCES GEOGRAPHY AND ENVIRONMENT Doctor of Philosophy CLIMATE CHANGE AND LANDSLIDE RISK ASSESSMENT IN THAILAND By Shotiros Protong The incidents of sudden landslides in Thailand during the past decade have occurred frequently and more severely. It is necessary to focus on the principle parameters used for analysis such as land cover/land use, rainfall values, characteristics of the soil and digital elevation model (DEM). Rainfall has increased in intensity. For example, the rainfall amount in March in 2011 was the highest in the previous 36 years (1974-2011). However, there was only one tropical cyclone that year. This situation was considered unusual compared to other years (TMD, 2011c). Landslide occurrences occur during intense rainfall especially in the rainy season in Thailand which usually starts around mid-May and ends in the middle of October. The landslide risk analysis is the focus of this research. The combination of geotechnical and hydrological data is used to determine permeability, conductivity, bedding orientation, overburden and presence of loose blocks. The regional landslide hazard mapping is developed using the Slope Stability Index SINMAP model supported by Digital Elevation Model (DEM) in 30 metres. So, the 30 metre pixel size of DEM is used to calculate on the ground. Geological and land use data are used to define the probability of landslide occurrences in terms of geotechnical data. The geological data can indicate the shear strength and the angle of friction values for soils above given rock types, which leads to the general applicability of the approach for landslide hazard analysis. To address the research, the following methods are described in this study: the calibration and the sensitivity of the SINMAP model for setup, geotechnical laboratory, landslide assessment at present calibration and landslide assessment under future climate simulation scenario A2 and B2. A2 simulation scenario delineates a very heterogeneous world and continuous population and economic growth, while B2 storyline is oriented on local solution to economical, social and environmental sustainability (START, 2010). In terms of hydrological data, the millimetres/twenty-four hours of average rainfall data are used to assess the induced rainfall landslide hazard analysis in slope stability mapping. The period 1954-2012 is used for the baseline of rainfall data for calibration of present-day conditions. Future climate simulation scenarios are downscaled in the local areas. The precipitation trends are needed to predict the future climate. The Statistical Downscaling Model (SDSM), is used to assess the simulation scenario of future change for latitudes 16 o 26’ and 18o 37’ and between longitude 98 o 52’ and 103 o 05’, is about 117,500 km2, covering Uttaradit province in the northern part of Thailand. The research allows the mapping of landslide risk, and indicates the spatial and time period of landslide occurrences. Thus, regional landslide hazard mapping under present-day climatic conditions from 1954 to 2012 and simulations of climate change from 2013 to 2099 related to the threshold rainfall values for the selected the study area are presented. Finally, the zonation of landslide risk will be compared and shown by areas (km2) in both the present and the future under climate simulation scenarios A2 and B2 in Uttaradit province. The rainfall trend will increase in the future simulation. The zonation of landslide risk is nearly the same between the present and the future simulation, while the failure region will obviously increase in the future, especially in steep slope areas. Key words: landslide hazard, GIS, Slope Stability Index (SINMAP), landslides, Thailand Table of Contents Table of Contents..................................................................................................................... i List of Tables............................................................................................................................. v List of Figures.........................................................................................................................xiii List of Accompanying Materials.................................................................................xxxiii DECLARATION OF AUTHORSHIP ............................................................................ xxxvii Acknowledgements .......................................................................................................xxxix Chapter 1: General Introduction and study area....................................................... 1 1.1 Aim and objective ................................................................................................... 3 1.2 Study Area ................................................................................................................. 3 1.2.1 General description......................................................................................... 7 1.2.2 Climate conditions ........................................................................................... 8 1.2.3 The past landslide .......................................................................................... 10 1.3 The conceptual framework............................................................................... 12 Chapter 2: Literature Review............................................................................................ 15 2.1 Distribution of rainfall across Thailand...................................................... 15 2.1.1 Introduction...................................................................................................... 15 2.1.2 The monsoons in Thailand....................................................................... 22 2.1.3 The low pressure area in Thailand........................................................ 23 2.1.4 Extreme rainfall distribution ................................................................... 25 2.2 The extremes of monsoon and typhoon in Thailand............................ 27 2.2.1 Introduction...................................................................................................... 27 2.2.2 The tropical cyclone in Thailand............................................................. 28 2.2.3 Case study of extreme monsoons, low pressure areas that led to rainfall occurrence, affecting landslides in Thailand (1999-2008) .................................................................................................................. 29 2.2.4 Case study of extreme tropical cyclone leading to landsliding in Thailand (2010 - 2011) ....................................................................................... 35 2.2.5 Tropical cyclones moving into Thailand during 1951-2011....... 37 2.2.6 The relationship between El Niño-southern oscillation (ENSO) and monsoon rainfall................................................................................ 40 2.3 Changes in rainfall pattern due to climate change ............................... 41 2.3.1 Introduction...................................................................................................... 41 i 2.3.2 IPCC simulation scenarios ............................................................................. 44 2.3.3 Climate change scenarios in high resolution at the local scale: downscaling ...................................................................................................................... 47 2.3.4 The regional climate model in Thailand................................................... 53 2.3.5 The relationship between climate and precipitation in Thailand............................................................................................................................... 55 2.3.6 The situation of ENSO in the present-day in Thailand......................... 56 2.4 Landslides...................................................................................................................... 57 2.4.1 Introduction........................................................................................................... 57 2.4.2 Type of landslides.............................................................................................. 57 2.4.3 The main factors affecting landslides in Thailand (DWR, 2010).........................................................................................................