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.. ,. N 00 00 t;1) 2 PROPOSED REVISION A revised PSIAC (1968) procedure would serve as a documentation tool for quantification of present and future impacts of conservation plans on rangeland. This revised procedure could also be used, to document, quantify, characterize and predict environmental impacts for rangeland planning in the preparation of National Environmental Protection Act documents. Modifications 1 through 7 relate to the over all character of the PSIAC sediment yield procedure. Modifications 8 through 16 are proposed updates to the actual rating of the individual PSIAC sediment yield fiwtors (a through i). MOdification 17 is a proposed revision of the PSIAC Sediment Yield Factor Rating Sheet. Modification 1: It is proposed that the title of the PSIAC procedure be restructured for consistent reference. The original docUment has a title page that presents either a miSleading title at' the top of the page Or at. best a cumbersome phrasing on ,the whole title page that leaves the user with a reference, to a committee rather than to a subject. It is proposed that the title be changed to: PACIFIC SOUTHWEST INTER-AGENCY COMMITTEE SEDIMENT ,YIELD PROCEDURE - REVISED 1991. The acronym PSIAC would still be valid for easy reference arid clear purposeful title with a date would be available for formal reference.' , ' , Modification 2: 'It is proposed that the PSIAC procedure' be considered applicable for 'land units as small as 100, acres as opposed to' the current lower applicability limit of 10 square miles. Renard, (1980) favorably compared PSIAC results with measured field data in 'watersheds, 100 acres or greater . SCs experience in PSIACratings .oriwildfire impacted' watersheds that drain 'into urbani:i:edareas along the wasatch, Front has found the PSIAC procedure to be applicable to units of 100 acres or greater' (Nelson and Rasely, 1989; Nelson and Rasely ,1990; Rasely and Robison, 1987; Robison and Rasely, 1988). , Modification 3: It is proposed that the PSIAC procedure does not necessarily have to be applied to complete hydrologic units. The PSIAC procedure may be applied to geomorphic units of 100 acres or greater. The geomorphic units can be defined on any combination of the following criteria: land use, climate; , precipitation, elevation, geology, soils, erosion condition, hydrology or other criteria that are used to determined that a landform is unique. This modification should be used with discretion to avoid excessive lumping or splitting of a watershed into too gross a division or too many divisions. In other words, PSIAC can be used for land use planning on major hydrOlogic units by dividing the hydrologic unit into appropriate geomorphologies. Modification 4: MOdification 3 presents the problem that a PSIAC rating in a geomorphic unit will be a rating on a land form and not