分析泥石流的孕育环境，根据分类分级与危险评价指标，作出自然过程层面的全国泥石流强度频度图、人文过程层面的全国泥石流损失危险图。

The regionalization boundary lines are mainly in light of the boundary of watershed. Because the occurrence and development ofdebris flow are all under the control of the range of watershed, which namely the synthetcal circulating system including many factors such as geology, landferm, hydrology, climate, ect, the rang of debris flow disaster is also under the control of the range of watershed. the whole country can be divided into four maijor are as according to the ocean where big river draft in and the extent of debris flow disater. The dangerous extent in whole major area and whole year or many years (namely in time and space) are not even, being of the characteristics of phaseand fluctuation. Because the dangerous extent in the same major area is different yet, it can be further divided into four degrees on the basis of debris flow characterstics. The dangerous extent in the debris flow distributed flow distributed area or active regions are not even too. The dangerous area of debris flow mainly locte at accumlative area and transporting area.
The active belt of debris flow has closely relation to gelogical structure, earthquake Debirs flows are mainly distributed on the sounthern slope with an elevation between 800-2500 meter and gradient between 25°～33°，the gully-type debris flows are mainly distributed in the ravines with a longitudinal 100‰～400‰. On the geology,debris flow distribution is under the control of active fault zone and the lithogy (soft statum or soft and hard altemated statum favour the occurence of debris flow). In the climate, debris flow distribution is under the control of rainfall and temperature, especially, the beavy rain in parts of an area, in a process of rainfall, serveral debris flow gullies are generated at the same time, beside, in the dry-hot river valley regions, debris flows frequent too. The unrasonble hiam economic activities as minings, bulding roads, denudation of forests and steep land cultivation are all the causes of debris flow generation.