Document type: DU ETD
Collection: Geology Theses  
Title A Regional Analysis of Eastern Colorado Streams and a Paleoflood Analysis of First Creek, Rocky Mountain Arsenal, Commerce City, Colorado
Author(s) Capesius, Joseph Peter
School/Department Department of Geography
Institution University of Denver
Degree Type Master's
Degree Name M.A.
Type of Resource text
Degree Date 1996 November
Digital Origin reformatted digital
Rights Statement All Rights Reserved
Reason for Restrictions No restrictions
Type of Restriction No restrictions
Keyword(s) Geography
Abstract This research examines the applicability of regional flood equations to streams in eastern Colorado. This research also attempts to explain why these equations fail to estimate the 100-year flood magnitude based on systematic and paleoflood data for First Creek, an intermittent stream that flows through the Rocky Mountain Arsenal, a National Wildlife Refuge. Paleoflood reconstruction uses woody debris, cottonwood tree age, and historic accounts as indicators of past floods. From these paleostage indicators, three paleofloods are determined to have occurred. These paleofloods have magnitudes of 3500 fe Is, 2000 fe Is, and tOOOfe Is. The tOO-year discharge determined from -II years of systematic streamflow data and the three paleofloods that occurred during a 30-year historic period is 4430 fe Is. This is substantially smaller than the tOO-year discharge as determined from regional flood equations of Jarrett and McCain (1976) and Livingston and Minges (1987). Three hypotheses are proposed to explain the failure of the regional flood equations to estimate the tOO-year discharge for First Creek. The first hypothesis examines basin lithology and unit discharge. This analysis shows basins developed in consolidated sediment have produced many large unit discharges (e.g., >500 fe Is/mi2)in eastern Colorado while basins developed in unconsolidated sediment have produced few large unit discharge. The second hypothesis shows that, when variations in surficial geology are controlled, maximum observed unit discharges are twice as large for stream basins located in high-relief areas (i.e., above 5000 ft elevation)as for basins located in low-relief areas (i.e., below 4000 ft elevation) in eastern Colorado. The analysis of the third hypothesis shows more extreme precipitation (>6 inches in 24 hours) events have occurred at sites less than 30 miles from large scale topographic rises than at sites beyond 30 miles from large scale topographic rises in eastern Colorado. These are areas with the greatest relief in eastern Colorado. The analysis of the regional flood equations shows that eastern Colorado may not be hydroc1imatically homogenous as previously assumed. This analysis further shows that high-relief areas may be more susceptible to extreme precipitation and flooding than areas with lower relief. Some researchers suggest greater precipitation and flooding occur near abrupt topographic rises in the western United States because of a combination of mechanical or orographic and convective uplift Future research in this area will undoubtedly improve the understanding of catastrophic flooding in eastern Colorado and other Rocky Mountain states.
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