Study of Potential Flash Floods by Kriging Method

Abstract

The flood frequency analysis has been widely conducted where gauging stations are available and statistical distributions can be used to analyze historical data. On the other hand, flash floods usually occur at unexpected locations having no gauging stations, and have hardly been discussed. Based on the available information from surrounding precipitation gauges, potential flash floods were defined for a watershed and their regional distributions were investigated. Daily truncation levels of 99.9 and 99.99% were used to derive potential flash floods, where a 99.9% level means that 0.1% of daily precipitations are larger than or equal to the truncated value. The higher the truncation level, the greater the magnitude of a potential flash flood. Records from 21 precipitation gauging stations were selected for the studied region. The kriging method based on the minimum variance unbiased estimation was introduced to calculate spatial interpolation. These kriging estimates form a regional distribution of potential flash floods, which are expressed by contour lines. The result shows that the estimation errors associated with the regionalization were reasonably small.