Laserfiche WebLink
1 <br /> ' IV. FLOODPLAIN <br /> General <br /> South Boulder Creek has a tributary drainage area of approximately 132 square miles at <br /> ' its confluence with Boulder Creek. The headwaters of South Boulder Creek are located <br /> at the Continental Divide. Gross Reservoir is located on South Boulder Creek upstream <br /> of Eldorado Springs. A U.S.G.S. stream gauging station is located on the creek <br /> downstream of Eldorado Springs where the drainage area is approximately 109 square <br /> ' miles. The peak flood of record at the gauging station which occurred in 1938 was 7,390 <br /> cubic feet per second (cfs). However, it is important to note that the gauge was not <br /> ' operational in 1894 when major flooding occurred in the Boulder Area and in the South <br /> Platte River basin. The Federal Emergency Management Agency (FEMA) regulatory <br /> ' 100-year flood discharge for South Boulder Creek at U.S. Highway 36 is noted to be <br /> 6,160 cfs as repotted in the Flood Insurance Rate Study for Boulder County (FIS). <br /> Previous Flood Studies <br /> ' In August 1969, the U.S. Army Corps of Engineers (Corps) published a Floodplain <br /> Information Report for South Boulder Creek. This report had a floodplain analysis for the <br /> Intermediate Regional Flood (approximately the 100-year flood) and the Standard Project <br /> Flood (approximately the 500-year flood). Flood profiles were developed from surveyed <br /> cross sections and the floodplains were delineated on U.S.G.S. 7 112 minute topographic <br /> maps with contour intervals of 10 to 40 feet. <br /> ' In December 1973, R.W. Beck and Associates published Major Drainageway Planning= <br /> South Boulder Creek. R.W. Beck defined the 100-year discharge for South Boulder <br /> Creek to be approximately 5,600 cfs. The floodplain hydraulics were analyzed through <br /> the use of a U. S. Bureau of Reclamation (USBR) backwater analysis model. <br /> i <br /> -8- <br />