Abstract: This paper was taking the Piliqing River Valley as the study area.Based on the FloodArea model, we simulated four flood processes occurred on May 2,2010,June 3,2012,May 9,2016 and June 17,2016 respectively in the region with the data about hourly precipitation,land use type,digital elevation (DEM) and the actual flood depth.Through the precision verification,the relationship between the rainfall and the flood depth was established which served as the basis to determine four critical rainfall thresholds corresponding to the four submergence levels.The results showed that the correlation between the simulated flood depth and the precipitation hit the best when there were eight hours of rainfall in the town of Karayagaqi with the value of 0.963.While for the town of Panjin,it was five-hour rainfall to achieve the best correlation at the value of 0.995.Comparing the simulated flood depth with the measured value on site indicated that the relative errors of the two sites,the town of Karayagaqi and the town of Panjin were 0.47 m and 0.1 m respectively with the error rate being 31.33% and 7.69% respectively.The results also proved that the FloodArea model has a good effect on the simulation of flood process in the study area,an ungauged mountainous region.According to the relationship between the flood depth and precipitation and the criterion of the mountain flood disaster level,the critical rainfall thresholds corresponding to the four levels at the warning point with 5 hours of precipitation accumulated were 17.84 mm for level 432.39 mm for level 354.21 mm for level 2 and 76.04 mm for level 1 respectively.

Key words: FloodArea model, Piliqing River Basin, flood simulation, critical rainfall threshold incurring disaster