中文摘要：

设计山洪计算是山洪灾害防治规划的一项重要内容，推理公式法是无资料地区小流域设计山洪计算的一种常用方法，但参数选取是否合适将直接影响到计算结果的精度。对推理公式法的参数规律进行了研究，提出了确定产汇流参数地理分布规律和暴雨参数空间分布规律的方法，并将其应用于乌鲁木齐地区，计算了无资料小流域的设计山洪，为制定山洪灾害风险区划提供了设计依据。

英文摘要：

The design flash flood calculation is one of the most important contents in the planning of prevention and cure flash flood disaster. The rational formula method is used to calculate design flash flood in an ungauged small basin frequently. But the result precision is affected by the parameters directly. The parameter laws of rational formula for design flash flood calculation of small basins in Urumchi region was studied in this paper. The research area is classified to gauged area and ungauged area. In gauged basin, design storm parameters（^-x, Cv, Cs） are got from annual maximum 24 hours storm amount data and design flood parameters（^-x, Cv, Cs） are calculated from annual maximum flood peak discharge data firstly. The calculated frequency P is confirmed by using random simulation technology. Then under the corresponding frequency, the design rainstorm and design flood are computed according to the frequency distribution curve. Using Genetic Algorithms and Reasoning formula method to inverse rainstorm parameters （n1/n2） and runoff yield and flow concentration empirical parameters （u／m） in gauged area. After analyzed the relation between empirical parameters （u／m） and drainage characteristic parameters （θ）, we find the trend lines in Urumchi region are as follows： m = 0. 14861nθ ＋ 0. 4952, u = - 23. 34251n （lnθ） ＋ 43. 7455. Using spatial analyze module and geostatistic analysis module in ArcGis, the spatial distribution map of storm parameters （n1/n2） in studied area can be obtained. Finally in ungauged basin, by using the map to confirm storm parameters （n1/n2）, by using the empirical trend lines formula to get parameters m and u, with the reasoning formula the design flash flood can be calculated. In this paper, a method to calculate the geographic distribution rules of flow concentration parameters and the spatial distributing rules of rainstorm parameters is put forward. It has been applied to Urumchi region and has got the design flash flood in a small