444 A NATIONAL PLAN FOR AMERICAN FORESTRY 



of plant cover to be eliminated, as is occurring about many of these 

 settlements, means lasting destruction of watershed-protection values. 

 How to correct this situation without destroying an already unstable 

 economic structure is a problem demanding most intensive study and 

 one the importance of which cannot be overemphasized. 



The danger of serious erosion resulting from construction of forest 

 roads on soils that are naturally unstable and that are readily eroded 

 has seldom been given adequate consideration within this basin. 

 In many instances abnormal run-off, accumulating in roads or in 

 drainage ditches built to protect roads, has cut veritable canyons in 

 slopes and valleys. In very few such instances has the erosion been 

 checked. Drainage methods that will turn water from mountain 

 roads before it has accumulated to destructive proportions, and 

 methods of developing a cover on bare cuts and fills, deserve much 

 greater attention. 



Because channel cutting is progressing at such a rapid rate, exten- 

 sive engineering works are justified as a supplement to restoration of 

 vegetation on slopes. The cost of engineering works adequate to 

 control the erosion would be considerable. 



Definite effort should be made promptly to control erosion and rapid 

 run-off from slopes by restoring tree growth, understory vegetation, 

 and litter. Intensive research is justified to determine just what 

 forest cover is most effective for each soil and forest type and what 

 use should be permitted. Where tree growth is necessary and where 

 devastation has reached such a point that tree growth will not come 

 back maturally, planting is recommended where it appears prac- 

 ticable. This would involve about 50,000 acres. Where the herba- 

 ceous vegetation has been so destroyed under open tree stands or in 

 openings in the forest that its restoration will be slow, artificial re- 

 seeding should be resorted to as satisfactory methods are developed. 

 Approximately 50,000 acres would appear to justify such reseeding 

 immediately. 



GREAT BASIN 



Adequate recognition has not been given to the need for watershed 

 protection on forest lands of the Great Basin, which consists essen- 

 tially of the eastward drainages of the Sierra Nevada of California, a 

 portion of southern Oregon, most of Nevada, the western part of 

 Utah, and small parts of southeastern Idaho and southwestern Wy- 

 oming (fig. 13). In this basin, drainage is all to the interior and, in the 

 main, timber values are low. Here the watershed-protective function 

 of forest lands derives its significance principally from the extreme 

 demand for water for irrigation agriculture and for urban use, the 

 scantiness of the water supply available, the danger of destructive 

 silt-laden floods or even mud-rock flows from local drainage areas, 

 and the necessity of protecting the soil against abnormal erosion and 

 of restoring soil productivity on certain mountain lands. 



DEMAND FOR WATER, AND RELATION OF FORESTS TO 

 WATER SUPPLIES 



Irrigation agriculture and its related industries are the basic perma- 

 nent industries of the Great Basin, although less than 2 percent of the 

 area is irrigated. Irrigation is the main support of most of the com- 

 munities. It is essential to such leading local industries as sugar man- 



