Comparative study on flash flood hazard assessment for Nam Ou River Basin, Lao PDR
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Comparative study on flash flood hazard assessment for Nam Ou River Basin, Lao PDR Jun Du1 · Zhong‑jie Fan1,2 · Jian Pu1 Received: 20 May 2019 / Accepted: 23 April 2020 © Springer Nature B.V. 2020
Abstract Laos is a mountainous, rainy and less developed country in Southeast Asia. In Laos, floods represent a major constraint on social economic development, causing a large number of casualties and property losses each year, among which the impact from flash floods is also very prominent. Especially in recent decades, with the development of social economy and the intensification of hydropower development, the serious threat from flash floods is becoming more and more obvious. However, there is no fundamental defence system for flash floods been established yet in this country, and the basic knowledge on local flash flood development is also ignored. For filling this gap, taking the Nam Ou River Basin as an example, this paper tries to find out the most helpful hazard assessment method for current Laos based on comparative analysis from the flash flood potential index, the calcu‑ lation of curve number–rainfall erosivity and the extrapolation method. The results show that the extrapolation method based on spatial lag model constructed by the data from Yun‑ nan, China, presents the most reliable outcome compared with the other two methods, indi‑ cating the spatial autocorrelation model can also be useful for extrapolation, effectively. Besides, the scale effect of different potential impact elements on flash flood, i.e. the spatial correlation between each element and the distribution of flash flood events at different spa‑ tial statistic units, was also preliminary studied. It is found that the degree of correlation in spatial analysis depends on the short board effect, i.e. only the element that restricts the regional flash flood developmental system can be the key factor. The correlations of most watershed elements increase or decrease directly with the rise of watershed scale, and the values of coefficients tend to be stable at large watershed scales. Keywords Flash flood · FFPI · Spatial autocorrelation · Hazard assessment · Scale effect
* Jun Du [email protected] 1
Research Center on Mountain Torrent and Geologic Disaster Prevention of Ministry of Water Resources, Changjiang River Scientific Research Institute, No. 23, Huangpu Road, Jiang‑an District, Wuhan 430010, People’s Republic of China
2
Chengdu University of Technology, State Key Laboratory of Geohazard Prevention and Geoenvironment Protection, Chengdu 610059, China
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Natural Hazards
1 Introduction The flash flood or mountain torrent here, as a kind of dramatic surface runoff that fea‑ tures abrupt rise and fall on water level, often develops in the hilly or mountain areas and becomes flooding in low-lying areas (National Weather Service, NWS). It is usually caused by natural or human factors such as rainstorm, snow melting or dam failure from natural or artificial dams. The abrupt rise and fall on water level are the
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