Mountain area is place where mud-rock flow is coexisting with humankind。mud-rock flow acts on mountain environment and strongly affects economic activities while human economic activities act on environment as well and intensely affect mud-rock flow。Frequent rainstorms can easily cause violent floods and mud-rock flow in mountainous areas。

mud-rock flow does harm to mountain environment and human safety with destroying the earth"s surface 。Human"s activity should follow natural law and exploite natural resources moderately in mountain area，otherwises such activities will destory mountain environment，increase activity of mud-rock flow and the situation would be wrose。If our activities obey natural laws， mud-rock flow harm will be controlled and the coordinate development of economy and mountain environment will be possible。