43G JOURNAL OF FORESTRY 



Storms and Flood of 1915. 



In 191 5 there were no storms which caused much damage, though 

 there was one storm greater in intensity than that of 1914. This storm 

 produced 9.85 inches of rain at Sunland, one inch of rain faUing in 

 an hour and fifteen minutes during the noon hour. Much water and 

 considerable silt, rocks, eroded soil, and debris were brought down the 

 stream and deposited in the wash of the stream, but the water failed 

 to reach a volume which would cause damage to lands outside the 

 canyon. 



During the year the check dams in the canyon were constructed, 

 some of them being in time to catch this storm. The result and 

 effect of these dams, installed in Empire Canyon, will be discussed 

 later. 



Storm and Flood of ipi6. 



The storms of January, 1916, were much heavier than those of 1914 

 and the heaviest for which there is any record in this locality. The 

 month began with a storm and the Los Angeles record for the first 

 ten days was 2.91 inches. On the fourteenth the big storm began 

 which lasted six days and produced a precipitation of 6.90 inches, 

 followed by another storm four days later which gave a precipitation 

 of 3.49 inches in five days. The first of these brought almost as much 

 water as did the one of February two years previous, and did as much, 

 if not more, damage, but the second storm caused by far the greater 

 losses, as the ground was completely saturated and the streams were 

 still at flood. 



The Effect of the Check Dams. 



In all, over five hundred dams have been constructed in this drain- 

 age basin, the greater portion being built of rock, though where the 

 bed of the stream was not stable brush fagots were used to prevent 

 the movement of the soil and to check the velocity of the water. More 

 of these dams were built in the upper reaches of the canyon than lower 

 down in order to keep the soil movement as high up in the area as 

 possible. The movement of small bodies of water down one of these 

 small side canyons was studied,* and it was found that with six dams 

 installed on a 23 per cent grade the velocity was changed to that of a 

 slope of 5.2 per cent. 



* Report of F. H. Olmsted in Board of Engineers Flood Control to Board of 

 Supervisors of Los Angeles County, 1915. 



