FLOOD01153

• County: Montezuma
• Community: Dolores
• Stream Name: Upper Dolores River
• Title: An Evaluation of the Dolores River at Dolores
• Date: 9/1/1992
• Prepared For: Dolores
• Prepared By: US Army Corps of Engineers
• Floodplain - Doc Type: Floodplain Report/Masterplan

Dolores River

Flood Hazard Information Report - Dolores River and
Tributaries. Dolores. Montezuma County. Colorado, September 1978,
by the Bacramento District, Corps ,)f Engineers. This report was
prepared for Montezuma County and the Colorado Water Conservation
Board and included a 15-mile reach elf the Dolores River going
upstrean from Dolores. The purpos'~ of the report was ". . " to
provide a basis for planning the b,~st use of lands subject to
inundat:.on by the 100-year flood." The Dolores portion of the
flood p:.ain is shown on Attachment 3.

Do:~ores River above Dolores. Ce>lorado. Flood Hazard
Informa1:ion Hvdroloav - Internal Office Report, November 1976, by
the Sacl:amento District, Corps of Engineers. The hydrologic
study duveloped a flow-frequency relationship of the Dole>res
River based on the recommended guidelines of the Water Resources
Council using streamflow data collectE~d at the "Dolores" and
"Below Hico" gaging stations.

HYDROLOGY

As noted above, the most recent: detailed hydrologic
investiqation of the Dolores River at Dolores was conducted by
the Corps in 1976. The results were basically the same as those
of much earlier studies by the Corps ]~os Angeles District and the
USBR. ]'EMA considered these data 'te> still be adequate for use in
its 1989 flood insurance study.

Apparently, some confusion halS existed through the years
that thu hydrology developed by the Corps conflicted with
hydrolo(~ developed by the USBR for the McPhee Project. As part
of this investigation, the USBR was c(mtacted to determine its
flow-fr'~quency for the Dolores River at Dolores. In response,
the USBH provided a copy of a memorandum dated 1 February 1985
(Append:Lx A) which states". . . we are now in agreement with the
Corps that the predicted 100-year flood at the Dolores River at
the Dolores gage has a peak value of :L4,500 cfs." A copy of the
USBR's analysis is included with the memorandum.

MUGh of the confusion has apparently been because the USBR
designed and built the Dolores leveE~s to prevent backwater
floodinq for a design capacity of only 10,000 cfs, the e}dsting
channel capacity at that time. This was documented in a
1 March 1985 letter to the Colorado Water Conservation Board
(Appendix A). The reason given for not providing a higher level
of protl~ction was that the USBR only had authority to mitigate
for project impacts and could not provide any additional flood
protection.

3