Minjiang valley is a fragile area in natural geography environment and forest ecological ecosystem according tolots of data of meteorology, geology, soil and hydrology, huge drop in topography, strong precipitation, easily eroded soil growing from granite, fragility to defend erosion in red soil area, water system of long handle sector and alternate with arrange canyon and basin vale benefit for collection water,and go against drain. The ability decline of defending soil and sluicing water, and hinder flood and flood detention for the degeneration of forest ecosystem. In consequent activity of people pick up water and soil loss, riverbed drive up, embankment fragility, ability of store flood water and row flood reduce. All of them make it snatur alcalamity (especially floodw ater) frequent .