Climate change and landslide risk assessment in Thailand

Protong, Shotiros (2016) Climate change and landslide risk assessment in Thailand. University of Southampton, School of Geography, Doctoral Thesis, 338pp.

Record type: Thesis (Doctoral)

Abstract

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 calcu late 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 modelfor 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 1954-2012is used for the baseline of rainfall data for calibration of present-dayconditions. Future climate simulation scenarios are downscaled in the local areas. The precipitation trends are needed to predict the future climate. The Statistical Down scaling Model (SDSM), is used to assess the simulation scenario of future change for latitudes16o26’and 18o37’and between longitude 98o52’ and 103o05’,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 periodof 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 areaare 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.