The semi-arid zone of the middle reaches of the Yellow River formed in some geological times

then

its naturaland environmental features appeared in the same time as follows: 1) the concentrated and fluctuated rainfall; 2)the sur-face material with loose structure; and 3.) the simple vegetation type and lower vegetative coverness. The characteristicsof erosion and Sediment-producing which were caused by the reoded environment are shown as; 1) the types of ero-sion and sediment are plentiful; 2)sediment layers are diverse; 3) the production of ediment is also characterized bythe natures of concentration and fluctuation. Finally

the authors put forward that it is difficult to change the fedturesof the semi-arid ecolongical environment

But

by means of the regulations of man-land relationship and landuse struc-ture and industrial structure

the people may control the deterioration of the eroded environment.