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<br />Large quantities of sediments were mobilized on hillslopes and in channels in the burned area during the <br /> <br /> <br />July 12th flood. A distinct black, burn boundary on rocks in pre-flood surfaces was used as a reference to <br /> <br /> <br />estimate the general surface erosion from sheet wash. Care was taken to estimate the general erosion <br /> <br /> <br />rather than the local erosion around the rock. In add~ion, pillars of soil were preserved under some <br /> <br /> <br />surface rocks and metal objects on the bumed areas. About a hundred hillslope measurements <br /> <br /> <br />throughout the study area suggest an average of about 10 mm of erosion. The area of maximum sheet <br /> <br /> <br />wash was limited to the headwaters of Shinglemill Creek, Spring Gulch, Sand Draw, and the upper third of <br /> <br /> <br />Spring Creek and also was used to help define the area of maximum rainfall. <br /> <br />Locally, small streams produced up to 6 m of scour, primarily by headcutting. Hundreds of trees, some as <br /> <br /> <br />large as a meter in diameter, toppled into the floodwaters, which exacerbated flood damages. Sediments <br /> <br /> <br />moved on hills lopes ranged from sm to cobble-sized material, and 2.5 m in diameter boulders were <br /> <br /> <br />transported in some channels. The distinct black, burn boundary on undisturbed trees and rocks in <br /> <br /> <br />channels were used to define prefire channel-bed levels and estimate the amount of channel change. <br /> <br /> <br />Many tributaries degraded during the July 12th flood, a~hough locally agradation (1-2 m) occurred along <br /> <br /> <br />Buffalo, Spring, and Shinglemill Creeks and on alluvial fans at tributary junctions in burned areas. Many <br /> <br /> <br />new fans had dimensions of about 100 m x 30 m x 1.5 m. September 1996 reservoir releases increased <br /> <br /> <br />flows in the NF South Platte River that were capable of transporting sediments from the Buffalo Creek fan <br /> <br /> <br />to South Platte, which produced about a meter of agradation in pools. <br /> <br />Flood-transported sediments and debris in Spring Creek dammed the South Platte River to a depth of <br />about 3 m, which caused backwater (ponding) and reduced the peak flow from Spring Creek. The peak <br />flow was 240 m3/s (+/- 20%) in the South Platte River downstream from Spring Creek (fig. 1, s~e 5), a <br />decrease of about 270 m3/s. W~hout this ponding and attenuation of the Spring Creek flood, the peak <br />flow at the South Platte River gage could have been as large as 595 m3/s. <br /> <br />10 <br />