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<br />. <br /> <br />. <br /> <br />. <br /> <br />" <br /> <br />. A large number of soil infiltration tests (approx. 25) were performed by manually <br />sprinkling water onto the ground in various parts of the watershed. It appears that the <br />soil infiltration is quite slow in most of the sites that were tested. The top layer of soil <br />was also scraped off for a number of sites, and the infiltration tests were repeated. <br />Similar results were obtained. Although the "hydrophobic" soil conditions may not <br />be a significant factor at this time, something about the soil type/soil structure seems <br />to prevent good infiltration of surface water. <br /> <br />. Sediments from the tributary streams and the burned watershed areas continue to <br />accumulate in the mainstems of Buffalo Creek and the North Fork of the South Platte <br />River. Huge quantities of sediment (in the form of alluvial fans, sand bars, and bank <br />deposits) were observed during the field visit. For example, at the Spring Gulch <br />confluence with Buffalo Creek (approx. 1 sq. mile drainage area) we observed a new <br />alluvial fan of about 4' deep, 200' wide, and 100' long. Since, July 1996, this fan has <br />eroded and reformed 7 times, which demonstrates the highly unstable nature of the <br />watershed. These sediments are continually being moved downstream toward <br />Strontia Springs reservoir. <br /> <br />. The streamflow gaging station located on Buffalo Creek downstream of highway 126 <br />was operating properly. (Greg 0 ' Neil of the USGS has confirmed that the gage is <br />operating properly at this time). Unfortunately, the channel bed of Buffalo Creek at <br />the gage site is changing oveT time due to scour, sediment loading, and channel <br />migration. The channel changes make it difficult to maintain a good rating curve for <br />the gage. We are working with Greg O'Neill to develop a rating curve using <br />discharge measurements (low flow), slope-area flood measurements, and slope-area <br />hydraulic analyses. <br /> <br />. The National Weather Service (NWS) will revise their precipitation thresholds for <br />flash flood advisories in the Buffalo Creek area. The NWS will issue a Special <br />Weather Statement for I" of rain in an hour. A flash flood warning will be issued for <br />2" ofrain in an hour. <br /> <br />. Overall, citizens and visitors in the Buffalo Creek area are still at risk for severe flash <br />flooding below the burned watershed areas. The streams that we are concerned about <br />at this time include Spring Creek, Spring Gulch, Shinglemill Creek, Sand Draw, <br />Buffalo Creek, and the North Fork.. <br /> <br />2 <br />