FLOOD05261 - Laserfiche WebLink

Home Browse Search

Flood Hazard Area Delineation For Lower Box Elder Creek Watershed An existing breached reservOIr (called the Terminal Reservoir) is located on a tributary to Upper Hayesmount Creek. The Terminal Reservoir (designated as 5DV2956) qualifies for nomination to the National Register of Historic Places. The site was evaluated as a potential historical property in the Final Environmental Impact Statement (FEIS) prepared for the New Denver Airport in 1989. In the FEIS, the City and County of Denver committed to preserve the site and prepare a formal nomination to the National Register. Upstream of the study area, a detention dam was constructed on Box Elder Creek near the Town of Elizabeth to help control flooding in the town. The U.S. Soil Conservation Service reportedly enlarged this dam in 1976. 2.4.3 Diversions The only significant surface water diversion in the study area is the diversion of the entire upper 12 square miles of Hayesmount Creek into Box Elder Creek, as discussed in Section 2.4.1 of the report. The Denver- Hudson Canal crosses the downstream portion of the study area. It intercepts runoff in Box Elder Creek and Lower Hayesmount Creek. 2.5 Flood History Much of the flood history described below is taken directly from the Upper Box Elder Creek Outfall Systems Planning Study Hydrology Report (CH2M-Hill, 1994)c According to information provided in the Arapahoe County Flood Insurance Study (FIS), three major floods have occurred on Box Elder Creek and in nearby watersheds in recent times (FEMA, 1993). The following is an excerpt from the FIS report (FEMA, 1989): In interviews held in Watkins, Strasburg, Byers, and Deer Trail regarding flood histories on Box Elder Creek, Comanche Creek, West Bijou Creek, and East Bijou Creek, residents recallcd severe damage and lost lives in floods occurring in 1905, 1935, and 1965. No estimates of historic peak discharges were given. The flood history of Running Creek (Upper Box Elder Creek) in the Elizabeth, Colorado area was documented in a Floodplain Information Report prepared for the Colorado Water Conservation Board (Water Resources Consultants, Incc, 1979)c The information in this report attests to significant flood events along the creek in 1935, when the bridge across the creek at Elizabeth failed, and in 1965c It was reported that flooding along Running Creek was less severe than in adjoining watersheds in both the 1935 and 1965 eventsc In 1935, flooding was most severe to the east, in Kiowa and Bijou Creeks. In 1965, flooding was far more severe to the east, in Kiowa and Bijou Creeks, and to the west, in Cherry and Plum Creeks. The flood history of Box Elder Creek was also documented at Bootleg Reservoir in a report produced by the staff of the Central Colorado Water Conservancy District (CCWCD, 1987)c The report mentions that major runoff events have occurred on Box Elder Creek at Bootleg Reservoir in 1924, 1935, 1942, 1948, 1957, 1964, 1965, 1973 and 1979. Among these events, Bootleg Reservoir (approximately 3,600 acre-feet) was completely filled in 1924, 1935 and 1973c The 1973 flood was one of the largest recorded floods on Box Elder Creek; it damaged portions of Weld County Roads 4, 8, 12, 14, 16, 22, 49 and 52 and destroyed private roads, driveways and livestock sheds. John Doerfer of UDFCD calculated that the peak discharge of the 1973 event may have been on the order of 6,000 cubic feet per second (cfs) at Bootleg Reservoir, based on anecdotal evidence of inflow and outflow rates (personal communication, 1999; CH2M-Hill, 1995). Another major runoff event may have occurred in 1949. Henry1yn Irrigation Company records document a large storm on June 12 and 13, 1949 that caused major damage to Lost Creek, the adjacent drainageway to the east Aerial photography of Box Elder Creek (dated June 14, 1950) shows evidence of substantial channel erosion from what must have been a major event occurring within one or two growing seasons prior to the date of the photographs. Dr. Robert Jarrett of the United States Geological Survey (USGS) has calculated the maximum paleoflood in Box Elder Creek at 1-70 (approximately five miles upstream of the study area) to be about 8,700 cfSc The discharges were calculated from estimates of flood width and depth corresponding to the height of paleostage indicators and channel slopec The Box Elder Creek golf course (located adjacent to Box Elder Creek at about 144th Avenue) received damage to greens and fairways during 1999 flow events. A flood event on August 5, 1999 on Bear Gulch Page 4 991-134cOOO Wright Water Engineers, Inc.