Evaluation of Rainfall Probability to Hazard Map in Laos PDR

Flooding in Laos has significant impact to both economic and sociological. Heavy rainfall is one of important factor to influent the magnitude of flood events. Therefore, it is important to understand the probability of rainfall in different return period and sensitivity of hazard area to the change in rainfall. This study, rainfall data from 33 stations and 30 years data length from 1970 to 2000 were used to generated the rainfall probability contour in different return period after that the integrated hazard map was use for comparison between the increase of rainfall intensity area and hazard area. We have developed an integrated hazard based on the combining 3 hazard maps which are flood, land use change and climate change hazard map. Analytical Hierarchy Process (AHP) is the tool for multi criteria decision making. This method used AHP as a tool to integrate the different hazard maps. AHP is used to provide the relative weights of the each hazards map. It is necessary to understand relative importance of each hazard map, by using the pairwise comparison matrix to compare their significance. The value of each row in pairwise comparison were determined based on the judgment of experts. The integrated hazard map divided into 4 categories as low hazard, medium hazard, high hazard and very high hazard. The results show that from different return period rainfall, mostly rainfall intensity increase in central and southern part of Laos after that we compare the results from rainfall intensity with integrated hazard map, the southern part have high and very high hazard area more than the central part of Laos.