FLOOD04773

• County: Montezuma
• Community: Dolores & Montezuma County
• Stream Name: Dolores River
• Basin: San Juan/Dolores
• Title: Dolores River near Dolores, Colorado Flood Insurance Study
• Date: 5/1/2004
• Prepared For: Dolores
• Prepared By: US Army Corps of Engineers
• Floodplain - Doc Type: Floodplain Report/Masterplan

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statistics among the different durations, and to provide cslimates for the missing rainl100d peak

110ws for the Dolores and Rico gages. After the low outlier years were rcmovcd from the

snowmelt data sets, the REGFQ program was run to analyze the snowmelt duration data for the

two gages.

8.4 Flow Frequency Curves. The REGFQ program provided statistics adopted for the

mill and snowmelt frequency curves for Rico and Dolores. The adopted statistics arc the

smoothed "frequency stalistics aller adjustmcnt" from the REGFQ runs. The snowmell and

rainl100d nov.' frcqueney curves tor the Dolores River bclow Rico gage are ploned on Plates 12

and 14, respectively (peak. 1-,34,7., IS-, and 30-day dural ions). with the duration data tabulated
on Plates 13 and IS. The snowmelt flow frequency curves (Peak. 14,34,7_, IS-. 30-, 60-, and 904

day durations) for the Dolores River at Dolores gage are plotted on Plale 16 and the data tabulated

on Plate 17.

The rainl100d peak now frequency curve for the Dolores gage required special treatment.

The data set included an estimated peak flow of 10,000 cfs for the October 191 ) event; longer

duration data for Ihc event arc unavailable. A special FFA run was made so that the peak

rainl100d statistics would match the statistics for the duration data. In this run, the 10.000 cfs

now was treated as a historic flood peak, the highest for the period 1896 to 2003. The missing

raintlooJ peak !lows (mostly for the period 1978-2003) were replaced by tlows estimated in the

REGFQ run. The set of FFA slatistics from the special run matched the set ofREGFQ statistics

for the other durations. See Plate 18 for the rainflood flow frequency curves (excluding the data

points for estimated peak flows) and Plate 19 for the labulalcd data. The higher magnitude

rainllood duration data (I-day to JO.day) at Dolores. and 10 a lesser extent at Rico. represent

general rain on sno\v after the maio snowmelt period.

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