A NATIONAL PLAN FOB AMERICAN FORESTRY 423 



Range area is covered with soils derived from sedimentary rocks such 

 as sandstones and shales, which absorb water slowly and when exposed 

 are readily eroded. Soils in the Sierra Nevada derived from lavas 

 and basalts also are easily eroded when well decomposed. On soils 

 of these classes the forest exerts a major watershed-protective in- 

 fluence by facilitating penetration of water from the heavy snow 

 blanket and by controlling erosion. 



In the Sacramento River Basin as in the San Joaquin Basin, the 

 woodland and brush areas have been classed as having a major 

 watershed-protective influence. The woodland and brush types 

 occupy nearly 25 percent of the area of the basin. Where dense, the 

 brush type forms a heavy mulch of litter on the soil, which retards 

 run-off and erosion principally by maintaining the soil profile at its 

 maximum absorptive capacity, its own absorption of water being 

 a minor factor. Unfortunately from the standpoint of watershed 

 protection, the owners of most private lands use fire to clear them or 

 open the brush. On sloping lands, destruction of the cover is nearly 

 always followed by severe erosion. 



Erosion control is particularly necessary in this basin because of 

 the importance of the reservoirs planned for the foothill belt under 

 the State water plan. There is grave danger that the largest of these, 

 the Kennett Reservoir in the upper Sacramento Basin, would fill with 

 silt very rapidly. On an area near Kennett, where smelter fumes 

 have caused complete destruction of all vegetation on upwards of 

 67,000 acres and partial destruction on 86,000 acres, "the hills are 

 everywhere cut and gashed by the long furrows which run from prac- 

 tically the top of the hills to the bottom in straight lines, growing 

 deeper and wider as they near the watercourses, which formerly were 

 forest-lined, and now are gravel washes in the summer and -torrents 

 during the winter". 68 



NORTH COAST DRAINAGES 



The north coast drainages extend northward along the Coast Range 

 from San Francisco Bay and include the Klamath River, which drains 

 a small part of southwestern Oregon east of the Cascades. Coniferous 

 forest occupies more than 55 percent of the area of these drainages. 

 Woodland occupies more than 15 percent of the area. Although 

 precipitation in the upper reaches of the Klamath River watershed 

 is about 20 inches or less, at some places along the Coast Range 

 precipitation reaches 80 to 100 inches, the highest in the State. 

 Most of this precipitation comes in winter, and at the higher eleva- 

 tions snow accumulates to considerable depths. Since precipitation 

 is heavy, the forest cover good, and the demand for water relatively 

 light, there is a considerable surplus of water over much of the drain- 

 age area, although in parts, such as the upper Klamath River, storage 

 is necessary to assure a sustained supply. In this upper Klamath 

 River area open volcanic soils absorb water so readily that the forest 

 exerts only a slight influence on watershed values. 



In the Coast Range serious erosion is possible, because of the heavy 

 precipitation, steep slopes, and soils that are eroded readily when 



8 Munns, E. N. Erosion and Flood Problems in California. Calif. State Board of Forestry Rpt. to the 

 1921 Legislature on S. Con. Res. 27. 1923. 



168342 33 vol. 1 28 



