Abstract: Shenfu-Dongsheng coal mining area is located on northern Loess Plateau,and is in the centre area of rainstorm of the middle reaches of the Yellow River.Soil erosion is very serious.Soil erosion intensity is mainly affected by rainstorm type,lasting time and intensity.In the region,there are not meteorological and hydrologic observation stations in some middle and small drainages,so to design and budget the rainstorm process is very important for us to calculate runoff process and erosion value of these drainages.For above-mentioned purpose,in this paper,according to the principle of hydrology and calculation formula(H_tp=I×t=A+BlnN/tⁿ×t),and on the base of characteristics of torrential rain in Shenfu-Dongsheng coal mining area,as well as on hydrologic count handbooks of Dongsheng city and Yuling prefecture(n=0.67~0.83,A=20~30,B=20~35;Average value:n=0.75,A=25,B=28),torrential values were calculated with various rainfall intensity and different reappear cycle of torrential rain.On the basis of the biggest torrential rain records of lasting 1,6,12,24 hours,the types of torrential rain process occurring once time yearly were conceptualized in various lasting rain,adopting the ways of average arithmetic,slide choose and correspondence main peak.According to about 10 years rainfall automation record digital data of ecological experiment base of Luidaoguo drainage in Shenmu county the designed rainstorm process curve were tested and verified.The results showed that lasting 1 and 6 hours rainstorm is the best fit with rate of above 90%,12 hours rainstorm is better fit with rate of about 85%,24 hours rainstorm is poor fit due to various rainfall intensity on curve of rainfall automation record.But the general trend is good fit.In this calculation way,the torrential rain process in the small drainage without observation station of meteorology and hydrology can be inferred.The inferred torrential rain process curve will be the foundation to calculate runoff formation and convergence.

Key words: small drainage, torrential rain process, design and budget, conceptualized rain type