四川省宁南县城后山泥石流激发雨强

INTENSITY EXCITING DEBRISFLOW AT THE HOUSHAN BY NINGNAN COUNTY TOWN, SICHUANP ROVINCE

根据宁南县城后山垂直剖面观测资料，对本区降雨的垂直变化及泥石流激发雨强作了探讨。当地暴雨泥石流发生所需的１０分钟雨强ｉ＿（１０ｍｉｎ）和前期降水量Ｐａ组合为：：ｉ＿（１０ｍｉｎ）≥１５ｍｍ∩Ｐａ≥５０ｍｍ，或ｉ＿（ｍｉｎ）≥１０ｍｍ∩Ｐａ≥６５ｍｍ，或ｉ＿（１０ｍｉｎ）≥５ｍｍ∩Ｐａ≥９０ｍｍ。超过上述各组合值就有可能暴发泥石流。

Ningnan County iS situated at the south reaches of Herigduan Mou ntain and belongs tomiddle mountain region. The riedmont of Houshan Mountain by Ningnan County is at 1200m,the altitude of top of it is at 2900m,relative height is 17 00m,and the horizontad range is only3.2km. There is a good positon to observe the clamtic elemen ts and research landslide and debrisflow activities in the middle region. In 1985-06-1988-12,there was a observatory at this region,The observed results areshown as following. 1.In rainy season(June-Sept.),the total precipitation and montmymean precipitation(June-Sept.)will be increasing-maximum-decreasing with the altitude lifiting. The maximunprecipitation appears at 2 200m. 2. The maximum rain intensities in 1d,1h and 10min all will be decrcasing-increasing-decreasing with the aItitude lifting. 3.Near 2200m,the rain intensities in 6h, 3h and 1h all will be maximum.It will have animportant action for debris flow formation. 4.The compsition for i_(10min)(rain intensity in 10min)and Pa(antecedent precipitation)tocause the rainstorm debris flow:i_(10min)≥15mm ∩nPa≥50mm,or i_(min)≥10mm∩Pa≥65mm,or i_(10min)≥5mm∩Pa≥90mm. When the composition values are over the obove values,the debris flow would occur.