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<br />001397 <br /> <br />SELECTION AND EVALUATION OF.MEASURES FOR REDUCTION OF <br />EROSION AND SEDIMENT YIELD IN THE PACIFIC SOUTHWEST <br /> <br />Introduction <br /> <br />The following material is intended to provide guidance in the selection <br />and evaluation of measures for erosion and sediment reduction in the <br />Pacific Southwest. The recommendations are for broad planning purposes <br />only and not for specific projects where detailed evaluations would be <br />required. <br /> <br />The evaluation of treatment needs considered in this report are for pur- <br />poses of erosion and sediment reduction without regard to other benefits <br />that mayor may not be gained by the improvements. While it is true that <br />several purposes are frequently achieved by the same treatment, priorities <br />of need and opportunities for success in treatment may not coincide for <br />the alternative purposes. The highest priority for sediment control is, <br />of course, the application of erosion control measures to the major sources. <br />However, in the case of some grazing lands, treatment of low contributing <br />or non-contributing sediment source areas having the potential for increased <br />forage production may be of benefit in reducing the stress exerted on ad- <br />jacent high sediment contributing areas. <br /> <br />For purposes of identifying erosion and sediment sources, reference is made <br />to the report of the Water Management Subcommittee, PSIAC, titled "Factors <br />Affecting Sediment Yield in the Pacific Southwest Area". When the erosion <br />and sediment source areas have been determined, erosion sites are broadly <br />classified as to whether they are the uplands or channels. In the former <br />instance the measures that are applicable are easily identified as "manage- <br />ment" and "land treatment" and the latter as "structural measures" and <br />associated vegetative controls. Management measures include proper uses of <br />the land and related resources to minimize erosion and sediment yield. Land <br />treatment measures usually include the purpose of holding the soil in place <br />by whatever means, including a reduction in rainfall impact and runoff, and <br />by increasing the resistance of the soil. The general purposes of structural <br />measures are to retard erosion at the site (head cutting, bank cutting, de- <br />gradation) and to provide a trap for sediment moving into the reach from <br />upstream. <br /> <br />Measures which Include Erosion and Sediment Control Purposes <br /> <br />Management and Land Treatment ~easures <br /> <br />The following list of measures and their definitions include most of those <br />now being used in the Pacific Southwest. <br /> <br />Measures for Range and Forest <br /> <br />Brush Control - Eradication of pinyon~juniper, sage, and other brush, and <br />replacement with more desirable vegetation. <br /> <br />