Laserfiche WebLink
<br />10 <br /> <br /> <br />~ either be justified by observed field conditions (and noted on the <br />QO' field rating sheet) or the ratings should. undergo are-evaluation <br />~ for consistency. It is also recommended that the raters confer in <br />.Iolo the field and determine if the total rating reflects their personal <br />view of the sediment yield and erosion status of. the geomorphic <br />unit. This determination may be characterized as a "gut reaction" <br />test - does the rating reflect what you see there? - a pertinent <br />question to consider before leaving the field. <br />, , <br /> <br />Modification 15: It is proposed that the title page following page <br />10 in the original PSI~C text be added to the page 10 text as a ' <br />major section title. This title should be centered and underlined.' <br />The title should be revised to read: "An Example of the Use of the <br />PSI~C Rating Sheet, for Evaluating sediment Yield"., The sediment <br />yield classification chart of modification 6 should be repeated. <br /> <br />The following example should be substituted for the 15 square miles <br />watershed: ~ geomorphic unit of approximately 1760 ,acres (1.75 <br />square miles) in,central Utah was evaluated for sediment yield. <br />The area is characterized by sagebrush vegetation with little <br />understory, roll.ing-hummocky badlands topography, in a thin silt- <br />loam soil with abundant calcium carbonate salt, dominated by <br />weathered Jurassic age Morrison formation shale with occasional <br />sandstone fragments on the surface. The following rating for the <br />Present condition was; performed: ' <br /> <br />Factors <br /> <br />a Geology <br />b soils. <br /> <br />c climate <br /> <br />d Runoff <br />e Topography <br /> <br />f Eff. Grnd. <br />Cover <br />g Land Type <br />Mgmt. Qual. <br /> <br />h Upland <br />Erosion <br /> <br />i Channel <br />Eros. and <br />Sed. Trans. <br /> <br />Sediment Yield Characteristics <br /> <br />Rating <br /> <br />Lacustrine shales, Jur-Morrison <br />Hi shrink-swell, dispersive, <br />hi CaC03, minor rock frags <br />Infreq convective storms, freeze~ <br />thaw dominant, appox 12" ppt <br />Hi peak flOWS, low volumes <br />60% area 15% slope = 9.0% <br />40% area 8% slope = 3.2% <br />Weighted slope Ave.= 12% <br />Veg 10%, Litter 5%, Rock 10% <br />Total Eff. Grnd. Cover= 25% <br />His.t. overgrazed, impacts <br />evident, pedestal erosion, <br />area mostly badlands <br />>50% of area involved in <br />conc. flow erose with minor <br />gullying <br />Moderate flow depths, minor <br />eroding banks and bed, 4th <br />order ephemeral gully develop. <br /> <br />5 <br /> <br />.8 <br /> <br />7 <br />5 <br /> <br />6 <br /> <br />8 <br /> <br />10 <br /> <br />25 <br /> <br />8 <br /> <br />Subtotal a-g = 39; Subtotal h-i = 33 <br /> <br /> <br />Total Rating = 72 <br /> <br />A total rating of 72 points is an annual sediment yield of 1.1 <br />