乌鲁木齐市无资料地区山洪泥石流临界雨量推求

Estimation of the Critical Rainfall Resulting in Outburst of Floods and Debris Flows in the Ungauged Areas in Urumqi, Xinjiang

确定暴雨山洪、泥石流临界雨量对于受影响地区防灾减灾具有十分重要的意义,本文根据暴雨山洪、泥石流的成因,计算乌鲁木齐山洪、泥石流临界雨量。有资料地区通过分析整理雨量资料来确定临界雨量;无资料地区假定灾害与降雨同频率,分析灾害次数,确定灾害发生频率,从而求出临界雨量。乌鲁木齐雨量站较少,无法绘制临界雨量的等值线。根据计算临界雨量值,利用反距离加权距离法进行研究区临界雨量空间插值,从而得出各小流域的临界雨量值。

Outburst floods and debris flows triggered by rainstorms are two kinds of natural disasters in mountainous areas where the vegetation coverage is low. They are extremely harmful to traffic and economic construction. Critical rainfall can be used to predict the outburst floods and debris flows. It is vital to confirm the critical rainfall, especially in ungauged areas. Based on the field survey and monitoring research for many years, in this paper the classification system of early warning the outburst floods and debris flows is developed based on their formation causes, and the critical values of rainfall resulting in the outburst floods and debris flows are calculated based on the statistical and analyzed results about the rainfall process in 15 days before occurring the outburst floods and debris flows in Urumqi region. For the gauged drainage basins, the critical rainfall is confirmed by analyzing rainfall records; for the ungauged basins, however, it is supposed that the occurring frequencies of natural disasters and rainfall are the same, and the critical rainfall is assured by surveying the occurring frequency of disasters. Because there are no enough data for drawing rainfall isolines due to the sparse distribution of meteorological stations in Urumqi, the inverse distance to a power method is used to map the critical rainfall in Urumqi and make certain critical values of rainfall in all the small drainage basins. The predicted 24-hour critical rainfall in Urumqi varies in a range of 13～25 mm. Urumqi belongs to an arid area. The criterion of critical rainfall resulting in the outburst floods and debris flows in such arid area can be classified into heavy rain （≥10 mm in average of 5 gauges in a rainfall area）, seriously heavy rain （≥30 mm in average of 5 gauges in a rainfall area） and rainstorm （≥50 mm in average of 5 gauges in a rainfall area）. It is demonstrated that the method is applicable for most mountainous areas in Urumqi and can provide a useful means to predict the outburst floods and debris flows.