泥石流源区砾石土的渗透过程是泥石流形成全过程中不可缺少的一个子过程，该研究对泥石流形成规律的认识和对泥石流汇流计算具有重要的意义。为此，笔者与日本学者一道选择蒋家沟支沟——大凹子沟的弱固结坡积物坡面做径流产流实验，实验区面积4000cm^2，实验用可控的头降雨，通过接收和量取超渗产流的量，判断土体是否达到稳定下渗，得出初始下渗率为0．55mm／min，参数口为0．56。通过下渗率与时间关系的曲线描述．建立泥石流源区砾石土的渗透方程，该方程可用物分析泥石流源区激发雨量过程的渗透规律，同时揭示泥石流源区产流过程地表径流的形成机理及其与流体能产生及流量的关系。通过大凹子沟1994-06-15-16日的降雨资料可计算出超渗产流为0．415mm／min．其总流量占泥石流总流量的17．8％。

Choose the debris flow original area, on loose gravelly soil slope, to do permeability experiment. The experiment area is 4000 cm². The Shower nozzle is used to produce rains. The precipitation is controlled by block up some of the hole on shower nozzle. Therefore, the infiltration rate is gotten. It is found that the rate of stable infiltration is 0 .11 mm/min. The initial infiltration is 0 .55 mm/min. From the test data the value of β is obtained, β=0.56. Therefore, the permeability formula be written as Fp =0.11+0.44e^-0.56t This rormula can be used to calculate the runoff resulted from excess rain in debris flow original area. The ratio of the amount of runoff to that of debris flow can be obtained. In terms of the raining processes of Dawazi gully between 0 ～ 12 o'clock on June 15 ～16, 1994, the runoff resulted from excess rain is gotten. It is found that the rate of runoff is 0.415 mm/min. This value take17.8% of the total discharge of debris flow.