Ch. 23] 



LAND MISUSE 



419 



witnesses, most of the important gullies of the Southwest began in the 

 1880's. Generally those in northern latitudes were cut at a somewhat 

 later date, but most were cut before 1900. By this time, the livestock 

 population equaled or was approaching that of the present, as indicated 

 by Fig. 3, and advocates of the overgrazing theory conclude that range 

 use had already been sufficient to disrupt the delicate balance between 

 aggradation and degradation previously established in these valleys. 



I860 



1870 



1880 



1890 



1900 



1910 



1920 



1930 



Fig. 3. Livestock population in western states, 1860-1930. Data from U. S. 

 Census reports. Livestock numbers have been reduced to common basis by con- 

 sidering 5 sheep equivalent to 1 cow or horse. Prior to 1890, animals on the 

 farm only were reported; beginning with 1890 the figures include animals both 

 on the range and on the farm. 



It is natural to assume that the first herds concentrated on the valley 

 floors, where the best feed existed and where water was available. 

 This subjected these vulnerable areas to intense and perhaps destruc- 

 tive use before more remote portions of the range were seriously af- 

 fected. This suggests, therefore, that the initial cutting was due to 

 lowering the resistance to erosion on the valley floors rather than to 

 changes affecting the runoff. 



It is also known, however, that the Southwest at least was subject to 

 large, if not unprecedented, floods during this same period, and prac- 

 tically every account of gully cutting mentions a rain or a flood of 

 extraordinary magnitude (see particularly Thornthwaite et at., 1942, 

 pp. 102-104; Woolley, 1946, pp. 87-90). As no stream-flow records are 

 available for the period, comparison with floods experienced since is 

 precluded, but precipitation data at a few stations in the Southwest 



