94 



MISCELLANEOUS PUBLICATION NO. 106.5. U.S. DEPARTMENT OF AGRICULTURE 



of the trash at the gin appears to be impractical — 

 the smoke produced is also a nuisance. Returning 

 the trash to the field is inadvisable unless it is 

 decontaminated of insect and disease pests. 



People living in the neighborhood of gins are 

 convinced that it is urgent to improve engineering 

 technology to effectively filter the air from gin- 

 ning operations, and to develop an inexpensive 

 technique to decontaminate gin trash enabling its 

 return to the fields as noninfesting organic matter. 



Analogous problems prevail around alfalfa 

 mills. 



Sediment 



There is no basis at the present time for a really 

 adequate estimate of the impacts of sediment upon 

 the national economy. The Army Corps of Engi- 

 neers has estimated that flood damage in down- 

 stream areas amounted to $538 million annually 

 tinder 1057 conditions and that, potential damage 

 under conditions in 1980 would be about $739 mil- 

 lion {120). The Soil Conservation Service has esti- 

 mated the average upstream flood damage in the 

 contiguous United States as being slightly in ex- 

 cess of $1 billion annually (4-3). Any separation of 

 flood damages between water and sediment com- 

 ponents can be only arbitrary at best, but it would 

 seem safe to guess that sediment damages asso- 

 ciated with floods, considering both upstream and 

 downstream areas, average at least about $500 

 million a year. 



Soil erosion is a natural geologic process which 

 has been accelerated many fold in most parts of the 

 country by man's use of the land. Reduction of the 

 rate of accelerated erosion is the only positive and 

 permanent cure for the sediment problem. How- 

 ever, the development and widespread application 

 of land management practices to control all ero- 

 sion is a dream of the future and specific measures 

 for transporting, storing, or otherwise handling 

 sediment will be required in many situations. But 

 before development of more acceptable land use 

 practices can be effectively pursued, increased 

 knowledge of the erosion processes and definition 

 of the basic principles governing the movement 

 and loss of soil must be attained. 



This research will involve study of detachment 

 and movement, of soil particles by raindrop splash 

 and flowing water, surface sealing and related 

 phenomena that result in decreased infiltration, 



water intake and movement through soil during 

 freezing and thawing periods, the role of plant 

 cover and crop residues in reducing erosion, and 

 concepts relating erosion to topographic, climatic, 

 and soil factors. Control practices need to be de- 

 veloped and integrated into systems that will re- 

 duce runoff a maximum amount and provide for 

 the safe removal of any excess drainage water. The 

 control practices for farms must be compatible 

 with modern farming methods, and for residential 

 and commercial development sites, with efficient 

 construction practices. Attention needs to be given 

 to the development of improved prediction 

 equations. 



The potential of land use and management prac- 

 tices for ameliorating sediment problems of water- 

 sheds and river basins is one aspect of the prob- 

 lem needing much further study. New concepts 

 and procedures for identifying critical sediment 

 source areas and predicting sediment delivery 

 from such areas as affected by climatic factors, 

 soils, geology, topography and land forms, stream 

 channel characteristics, erosion-control practices, 

 and watershed protection measures are required. 

 Increased knowledge of the physics of sediment 

 genesis and movement in watershed systems is re- 

 quired for isolation and selective treatment of 

 critical sediment source areas. 



Criteria for the engineering design of sediment 

 traps and debris basins are inadequate. A better 

 understanding of the mechanics of sediment trans- 

 port in tortuous channels of alluvium, and the 

 resistance of cohesive materials in channels to hy- 

 draulic forces is necessary for design and mainte- 

 nance of stable stream channel sj-stems. 



Additional information on rates and processes 

 of sediment deposition in reservoirs and water de- 

 tention structures, on floodplain lands, and in 

 estuaries and harbors will also be required for 

 effectively coping with sediment, problems. 



Little or no information is available on the role 

 of sediment as the transporting agent for residues 

 of pesticides and other chemicals in streamflow. 

 The affinity of sediments, particularly clays and 

 organic fractions, for pesticides must be defined 

 and, if significant, measures for keeping such 

 wastes from streams must be developed. More eco- 

 nomical and effective techniques to stabilize 

 streambanks are required. New technology to sta- 

 bilize eroding soil in developing urban areas, on 



