A NATIONAL PLAN FOR AMERICAN FORESTRY 317 



Cces almost lacking, under a deep duff. Where this covering has 

 n burned, the soil itself is practically destroyed. Studies by the 

 Appalachian Forest Experiment Station on a 1924 burn in West 

 Virginia indicated that spruce and hardwood litter from 12 to 18 

 inches deep was destroyed. In his report on the southern Appa- 

 lachian region, which had a large influence in bringing about the 

 purchase of national forests in the eastern United States region, 

 Glenn 21 said of the Blackwater Basin in Virginia : 



All of the Blackwater Basin except its lower part has been thoroughly lum- 

 bered and then burned over, so that in many places the bare rocks are exposed 

 and scarcely anything but briers and fire-scald cherries have since been able to 

 take hold. It will be years before a commercial forest can be started and cen- 

 turies before the magnificent hemlock, spruce, and pine that once covered it can 

 grow again. 



In the 20 years since this prediction was written, conditions have 

 not materially changed on large areas, and the Forest Service has 

 been obliged to plant part of the present Federal holdings. 



In the chaparral type of California, a type characteristic of water- 

 sheds of critical importance to a large population, hot summer fires 

 destroy the entire cover on thousands of acres every year, often 

 leaving several inches of ash on steep slopes completely exposed to 

 erosion. If the fall and winter precipitation comes as mild, well- 

 sustained rains, studies of the California Forest Experiment Station 

 have shown that a good cover of annuals will come in, and that these, 

 together with sprouts from such crowns of shrubs as remain alive, 

 may be sufficient to hold much of the soil in place. However, these 

 rains are more apt to come as semitorrential downpours before an 

 adequate vegetative cover has become reestablished and then great 

 quantities of soil are washed from the slopes in the rapid unobstructed 

 run-off. 



Hoyt and Troxell 22 have compared the run-off of Fish Creek with 

 that of Santa Anita Creek, neighboring watersheds, for the 7-year 

 period from October 1917 to September 1924 when both were covered 

 with forest and chaparral, and then for the 6-year period following a 

 fire in the fall of 1924 which denuded the Fish Creek watershed. 

 In the first year following the fire they found a 23 1 percent increase in 

 run-off over their estimated normal of 1.07 inches and an increase of 

 1,700 percent in the maximum daily discharge resulting from the first 

 four storms occurring after the fire. The peak discharge, which was 

 ordinarily 2.5 times the maximum daily discharge prior to the fire, 

 increased to 16.2 times on April 4, 1925. 



Figure 1 indicates very clearly the enormously increased flood 

 flows from Fish Creek and an adjoining burned watershed following 

 heavy rains. In this graph the average daily rainfall at Mount Wilson 

 and Santa Anita Ranger Station, in or near these watersheds, are 

 contrasted with the combined daily run-off records of the United 

 States Geological Survey for Fish and Sawpit Creeks (together with 

 the flow in the Monrovia pipe line which comes from Sawpit Creek) 

 for the spring of 1924, before the fire, and of 1925, after the fire. 



During the second year after the fire Hoyt and Troxell found an 

 increase of 26 percent above the estimated normal in the run-off from 



21 Glenn, L. C., "Denudation and erosion in the southern Appalachian region and the Monongahela 

 Basin." U.S. Qeol. Sur., Prof. Paper No. 72., 1911. 



Hoyt, W. G., and Troxell, H. C., " Forests and Stream Flow," Proc. Amer. Soc. Civil Engin., pp. 1037- 

 1066. Vol. 58, August 1932. 



