Abstract
A probable rapid sea level rise (SLR) caused by global warming seems to have a great impact on environmental conditions and human life in coastal regions all over the world. It will induce natural disasters such as various types of floods and change of land use, vegetation, geomorphological conditions and hydrological circumstances. For the reason, a detailed preliminary assessments of the impact is required in order to implement measures to counteract SLR by many governments.
It needs enough budget and time to evaluate the total loss by the impacts. But it is difficult to do so particularly in developing countries, because we can not get enough information of ground elevation and areal distribution of properties there. Then the unit value method which enables us to evaluate the loss easily was developed in combination with land use information and data of socio-economic properties in Thailand.
Since there is a lack of basic information, remote sensing using satellite data is effective for evaluating total loss of socio-economic properties. In this study, socio-economic properties were calculated reasonably in combination with unit values, land use information using LANDSAT image, and ground elevation data in Bangkok area. The area is located near the river mouth of the Chaophraya and it might be easily affected by SLR.
Socio-economic properties consist of real estate, productivity and residential population. In this study, the unit values are defined as the density of these properties per 1 rai (1 rai is 1, 600m2), 1m2, and 1km2.
The values of the real estate were prepared based on a socio-economic data book, interview survey and local researchers' comments. We applied the highest value to commercial area, the lowest value to agricultural area, one to fifth of the highest value to residential area and industrial area, and 10 thousand bahts per rai to fish pond.
The values of the productivity of commercial, residential, industrial, and agricultural areas were calculated by the following process. Total productivity of every category of industry, agriculture, commercial and residential was divided by the areal extent of each land use in Greater Bangkok Metropolitan Area. The value of the productivity of fish pond was prepared based on a socio-economic data book. The value of residential population was calculated by the following process. Total residential population in every administrative unit was divided by the total of residential and commercial areal extents in every administrative unit.
If 1m SLR occurs in future, we can estimate the followings: 1, 200km2 of land is submerged and it means loss of approximately 64 billion bahts. As for the productivity, 300 billion bahts per year are lost. 2 million 800 thousand of residents have to be withdrawn inland. As for total loss of socio-economic properties, about 20% of difference occurred in the estimation based on two kinds of maps between LANDSAT land use map and conventional one by NRCT (National Research Council of Thailand).
The total loss estimated here provides an extreme case in which any countermeasure is not completed.
