424 JOURNAL OF fore;stry 



front face be made approximately three times the depth of the unob- 

 structed stream it will cause the direction of the stream to be changed 

 when it drops over the dam to a new one nearly at right angles to 

 the one held originally. Thus at the face of the dam all motion in a 

 forzvard direction is checked, and then this water is let vertically 

 downward, so that by this process the elevation is overcome. The 

 water during these drops attains a high velocity, but, as it is at no 

 place in contact with the stream bed during its plunge, no erosion can 

 take place and the energy of the fall can be dissipated upon an apron 

 or water cushion at the foot of the dam. Thus water may be stepped 

 down, so to speak, from one level to another, and if so built that the 

 top of one dam is at the same level as the base of the next higher one 

 there can be but little erosion. 



In the settling basins behind the dams debris, rock, and sand are 

 deposited, and as time passes and repeated high waters bring the soil 

 down from the canyon slopes, these settling basins receive and hold 

 more and more debris and become storage reservoirs in addition to 

 checking the velocity of the stream, holding back the water and per- 

 mitting its escape gradually after the storms are over. This effect 

 may quite possibly extend well into the summer months, or, as in 

 those cases where there is an underground artesian basin, may permit 

 this water to escape from the canyon bed directly into the artesian 

 basin, where it manifests itself in the rise of the water in walls tapping 

 the basin. 



HAINES CANYON AND THE SUNLAND DRAINAGE BASIN. 



The Sunland drainage basin, in which this work has been done, is 

 an area of 6^ square miles, i^ square miles of which lies in the 

 Angeles National Forest. This portion is in the Haines Canyon 

 watershed, while the remainder includes, in general, open cultivated 

 valley lands. 



From the standpoint of flood waters, Haines Canyon is the most 

 important part of this drainage basin. It is a steep, narrow watershed 

 running up from the valley floor, at 2,000 feet elevation, to the summit 

 of Sister Elsie Peak, which has an elevation of over 5,000 feet, and 

 was burned over by an intense fire in September, 191 3, the chaparral 

 cover being completely destroyed. The soil is relatively deep, and is 

 composed of a gravelly loam carrying considerable rock, varying in 

 size from pebbles up to large angular fragments. The underlying 

 rock, granite, is badly decomposed and much of the soil is derived from 



