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<br />in the tim1ng of the bursts. No explanat10n for
<br />th1s difference in timing has been determined.
<br />The bursts in the adopted mass curves 1n this
<br />stuqy were timed according to the reported times
<br />of peak discharge occurrences (Table 2).
<br />
<br />Table 2. - Time (MDT) of flood peak
<br />discharges, July 31, 1976
<br />
<br />Stream and location
<br />
<br />~eported Reconstructed
<br />time time-
<br />
<br />Big Thompson Rher at Glen Comfort
<br />~ig Thompson River at Drake
<br />
<br />2000 2010
<br />2100 2050
<br />2300 2320
<br />2230 2100
<br />!/2130 2100
<br />2100 20AD
<br />231)0 2220
<br />non 2220
<br />~------------~---
<br />
<br />Big ThOl1lpson R;ver at mouth of can)'on
<br />
<br />Dry Gulch at mouth below LakeF.stes
<br />
<br />Recorder chart, Big Thoo~lSon Rher at
<br />EslesParlcaboYeLakeEsles
<br />Fo'~ Creek near Glen Haven - Fi rst peak
<br />-Seconrlpeak
<br />NorttlForkB1gThompsonatDrake, as shown
<br />by recorder chart
<br />
<br />11 The recorder chart of the Big Thompson River at Estes Pari< was con-
<br />sldered in this study tn be a more reliable guide to flood peak time
<br />of Dry Creek at mouth than the chart of the gage below Lake Estes.
<br />
<br />11
<br />
<br />10,04 Inches
<br />
<br />~ '0
<br />W
<br />I
<br />U
<br />Z
<br />
<br />
<br />~ 8
<br />~
<br />:'.
<br />;;
<br />~ ,
<br />~
<br />
<br />Curve A for subbasin
<br />6 (near- Glen /--'-
<br />Comfort)~
<br />/
<br />I
<br />/
<br />I
<br />I
<br />I
<br />"
<br />/ /
<br />/ /
<br />/ /
<br />//"
<br />
<br />o
<br />
<br />w
<br />>
<br />~ 4
<br />~
<br />~
<br />"
<br />"
<br />"
<br />u
<br />
<br />o
<br />1830
<br />
<br />2230
<br />
<br />2330
<br />
<br />1930
<br />
<br />2030 2130
<br />TIME (MDT)
<br />
<br />Figure 9. Comparison of mass curves developed in this study
<br />(dashed-line curves) with those developed by Maddo~ et a1.
<br />(1971) using L1mon reflectivity data (solid-line curves).
<br />Curve A 1n Figure 5 was applied to the 4-hour average pre~
<br />c1pitatlon for subbasin 6 (above Glen Comfort) for compar-
<br />ison with' the Glen COIIfort curve. Curve C in Figure 5 was
<br />appl fed to the 4.hour average precipitation for subbasin 0
<br />(above Glen Haven) for comparison with the Glen Haven curve.
<br />
<br />4.
<br />
<br />CONCLUSION
<br />
<br />This stuqy illustrates the value of
<br />streamflow data 1n the analysis of severe
<br />storms, espeCially where reliance IIlJst be made
<br />on bucket-survey type of rainfall data. In th1s
<br />instance, peak d1scharge data were essential 1n
<br />identifying the locations and intens1ties of the
<br />storm centers. The 4-hour precipitat10n pattern
<br />(Figure 4); the mass curves (Figure 5); and the
<br />precipitation depth-area-duration curves (Figure
<br />8) are believed to represent the best analys1s
<br />of this storm that can be made on the bas1s of
<br />available meteorological and hydrolog1cal infor-
<br />mation.
<br />
<br />,
<br />
<br />"
<br />
<br />ACknowled~ents. - Th1s studY was performed under
<br />tne gener supervision of ~. Leon Hyatt, Chief
<br />Hydrology Branch. Typing and ed1t1ng serv1ces
<br />were performed by Edythe Pa1ge, Marilyn Espe9ren,
<br />and Evelyn Butler. The figures were drafted by
<br />Gene Sanders and Randolph Miller. Photocopying
<br />and dup11cating support were prov1ded by Anthony
<br />TralOOtolo and Jerald Spath.
<br />
<br />REFERENCES
<br />
<br />Bureau of Reclamat10n, 1973: DeSirn of Small
<br />Dams (2nd Edition), Denver, Co orado,
<br />u:s. Government Printin9 Office, B16 pp.
<br />
<br />Clark, R. A., 1971: Desi9n Storm Potential Above
<br />Coachella D1kes 2 and 4, Consultant's Memor-
<br />andum, ,Flood Hydrology Section, Denver,
<br />Bureau of Reclamation, Eng1neering and
<br />Research Center, 12 pp.
<br />
<br />Grozier. R. U., J. F. McCain, L. F. Lang, and
<br />D. C. Merriman, 1976: The Big Tho~son River
<br />Flood of July 31-August I, 1976. Denver,
<br />Colorado, U.S. Geological Survey and the
<br />Colorado Water Conservation Board, 78 pp.
<br />
<br />Maddox, R~ A~, F. Caracena, L. R. Hoxit, and
<br />C. F. Chappell, 1977: Meteorological Aspects
<br />of the Big Tho~son Flash Flood of 31 July
<br />1976. Boulder, Colorado, NOAA Technical
<br />Report ERL 3B8-APCL 41, U.S. Department of
<br />Commerce, National Oceanic and Atmospheric
<br />Admin1stration, Environmental Research
<br />Laboratories, 83 pp.
<br />
<br />-- MlJmford, J. A., 1975: Flood Hydr09raph by
<br />Unitgraph Procedure, Program User Manual.
<br />Denver, Colorado, Bureau of Reclamation,
<br />Eng1 neer1ng and Research Center, 17 pp.
<br />
<br />,197B: Streamflow Routing by
<br />Modified Wilson Procedure, Program User
<br />Manual. Denver, Colorado, Bureau of Reclama-
<br />tion. Eng1 neering and Research Center,
<br />15 pp.
<br />
<br />National Weather Service, 1977: Big Thompson
<br />River, Colorado, Total Precipitation July
<br />31-August 2, 1976. Kansas City, M1ssouri,
<br />Central Re9ion, National Weather Service,
<br />1 p.
<br />
<br />U.S. Geological Survey, 1977: Water Resources
<br />Data For Colorado, Water Year 1976, Vol. I,
<br />Missouri River Basin, Arkansas River Basin,
<br />Rio Grande Basin. Denver Federal Center,
<br />Lakewood, Colorado, U.S. Geolog1cal Survey,
<br />311 pp.
<br />
<br />142
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