Climate and accelerated erosion in the arid and semi-arid Southwest, with special reference to the Polacca Wash drainage basin, Arizona
Thornthwaite, C.W.; Stewart Sharpe, C.F.; Dosch, E.F.
US Department of Agriculture Technical Bulletin 808
Accelerated stream trenching or arroyo cutting in the Southwest during the last half century has caused widespread damage to agricultural and range lands. Under natural conditions in the Polacca Wash and in most of the Southwest, the plant cover protected the soil and retarded the flow of water off the lands, but as a result of irritations of various forms, erosion was accelerated, and short discontinuous gullies became numerous. These lengthened and became joined to form continuous trenches. This gully cutting has been most conspicuous and destructive, but sheet erosion and wind erosion are also reducing the value of the lands. Various workers have attributed the current erosion damage to climatic change, but careful analysis of the climate shows that there has been no significant climatic change in the Southwest in the last 2000 yrs. The accelerated erosion that is damaging the lands of the Southwest appears to have been caused by man, and by proper methods man can check it and reclaim the land for his use.