Landslides,debris-flows and other disasters along roads caused by precipitation occur frequently,be-coming one of the most important factors of roads damages.Yunnan,Guizhou,Sichuan and Chongqing are especially prone to road damages.Based on the information of road damages,the corresponding precipitati-on data from January 2007 to July 2013 and 24 h precipitation forecast data from July 2012 to July 2013, probability forecast models are adopted to describe probabilistic relations between precipitation and road damages.First,precipitation factors of the day and over the past two,three,four,five,six,seven days and effective precipitation over the past 15 days are analyzed by the method of Kendall correlation,and precipitation of the day and the past effective precipitation are identified because of small correlation.Sec-ond,after the normality process to two factors,polynomial fitting,Fourier fitting and Gaussian fitting are applied to the frequency distribution of the disaster and two kinds of precipitation factor.According to the analysis of fitting correlation and the fitting error,Gaussian fitting method is selected to apply to the scat-tering distribution of precipitation and road damages.Finally,universal probability forecast models of road damages based on effective precipitation (Model Ⅰ)and comprehensive of the day and effective precipitati-on (Model Ⅱ)are established,and the fitting adjustable coefficients are 0.9108 and 0.8333,respectively. According to critical precipitation thresholds of two models,combining the grade of hazards risk and pre-cipitation risk to road damages,two kinds of warning classification scheme based on precipitation are pro-posed.Two risk forecast models for road damages are developed.Risks of road damages are divided into five levels by probability of damage occurrence:Very small,small,medium,large and very large.Two risk forecast methods are tested,showing they are both applicable to describe the relation between precipi-tation and road damages,and have a high forecasting accuracy and strong reference value in disaster fore-cast.In comparison,two models have the same trend and results of Model Ⅱ are generally greater than Model Ⅰ in number.In the flood season and disaster-prone period,Model Ⅱ is more sensitive to subjec-tive forecasts than Model Ⅰ.The risk forecasting systems of road damages are created for Southwest China based on two methods,and used in risk operation since the end of 2012 achieving good effects.%降水引发公路沿线滑坡、泥石流及其他灾害频繁发生，已成为引发公路损毁的最重要因子之一。该文利用2007年1月—2013年7月区域（云、贵、川、渝4个地区）公路损毁灾害数据、基础地理信息数据及国家气象中心降水量历史资料，通过对灾害发生频次、降水量等资料的统计分析，初步探讨降水与公路损毁灾害的关系，并重点针对公路损毁的降水影响因子（即前期有效降水和损毁灾害发生当日降水），开发具有普适性的公路损毁概率密度函数及其概率拟合方程，建立公路损毁灾害概率预报模型；综合公路损毁灾害风险区划信息（即灾害危险性等级）与降水的等级临界阈值（即降水危险性等级），建立区域公路损毁的危险性分级预警方案，得出综合的西南地区公路损毁风险预报模型，以1～5级划分，分别为灾害发生可能性极小、灾害发生可能性较小、灾害发生可能性中等（注意）、灾害发生可能性较大（预警）、灾害发生可能性极大（警报）。该预报方法结合降水危险性等级及公路损毁灾害危险性等级，明显优于仅考虑阈值降水量的判别方法。
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