432 peterson. PROBLEM OF GULLYING [Ch. 23 



rose briers have become established on the gully floors. Figure 5c 

 shows filling on the floor of a gully in northern New Mexico. Here 

 a moderately dense growth of grass, weeds, and shrubs has been suffi- 

 cient to trap silt and clay originating from an active headcut located 

 a few hundred feet upstream. Deposition in this locality is of unusual 

 significance in that it has occurred during a drought period when other 

 gullies in the vicinity were actively degrading. Studies of this and 

 other aggrading reaches will perhaps furnish information regarding 

 methods that might be employed to increase the gradient of deposition 

 behind barriers. 



NEEDED RESEARCH ON GULLIES 



Irrigation and stock raising constitute the backbone of industry in 

 the western states. With both being jeopardized at a constantly in- 

 creasing rate by gullying and other forms of erosion, research aimed at 

 developing feasible methods of control is patently a necessity. To be 

 successful this research will need to be directed into all elements of the 

 problem, from geology and ecology to the practical phases of engineer- 

 ing and range management. The writer makes no pretense of being 

 in a position to outline such a research completely, but on the basis 

 of considerable experience within the area, the following generalized 

 subjects are suggested as fundamental to the problem. 



Because re-establishment of aggradation within the gullies and on 

 the valley floors offers the only permanent cure for erosion, geologic 

 studies should be undertaken to determine the conditions existing dur- 

 ing previous periods of valley filling. This will involve all phases of 

 the sediment history of the valley, from the initial weathering of the 

 source rock through its transportation to final deposition and possible 

 alteration since. Pertinent questions which need to be answered in- 

 volve the factors that were most important in establishing former pro- 

 files of stream equilibrium: grade; magnitude of flow; sediment load; 

 character of the sediments; vegetative cover on the watershed as a 

 whole or more particularly on areas where aggradation took place. 

 As reasonably accurate answers to these questions are found, com- 

 parisons will be possible with existing conditions under which streams 

 are actively degrading. The same questions relative to factors in- 

 fluencing such action will again need to be answered, but with addi- 

 tional ones aimed at determining the possibilities of favorably altering 

 these factors by engineering structures or land-management practices. 



Information on the history of the eroding valleys, particularly with 

 regard to the recurrence of degradational and depositional cycles, needs 



