FLOOD08448

• County: Montezuma
• Basin: San Juan/Dolores
• Title: Hydrology Addendum Montezuma County
• Date: 11/1/2000
• Prepared For: County of Montezuma
• Prepared By: CWCB
• Floodplain - Doc Type: Floodplain Report/Masterplan

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are no longer active, However, most of these gaging stations do not contain enough data to
calculate peak discharges, The gages for which adequate data available for peak discharge
calculations are shown in the following section of the report, There are also several gaging
stations upstream and downstream of Montezuma County along the Dolores River,

F100dine Problems and F100dine Historv
Floods in the subject watersheds normally occur during the months of late summer and early
autumn and are caused primarily by intense localized cloudbursts or thunderstorms, Typically,
these floods have high peak discharges with low volumes over short durations and there is
usually a very short window of opportunity for flood warning and evacuation once a major
storms hits the area, Less damaging floods can also result from rapid melting of mountain
snowpack in the spring and early summer months, especially on the larger drainageways. A
combination of rainfall and snowmelt can sometimes prove to be the worst flooding scenario for
Colorado's mountain streams,

The FIS reports major flood events in 1909, 1911, 1932, 1937, 1938, 1941, 1944, 1949, 1957,
1973 and 1979, with the 1911 flood being the largest flood on record in the Dolores and West
Dolores Rivers, Flood losses in the West Dolores River, Dolores River and Lost Canyon Creek
are usually limited to damage of bridges and inigation structures, The floods of 1909 and 1911
caused damage to commercial and residential structures in Mancos, while the floods of 1973 and
1979 primarily caused significant bank erosion,

Previous Studies
Previous Flood Hazard Boundary Maps (FHBMs) were prepared for Montezuma County in 1977,
The FIS updated information in the FHBMs based on more detailed hydrologic information,
Flood Insurance Studies have been developed for both the Town of Dolores and the Town of
Mancos,

Community Response to the CWCB Deshmation and Approval Process
A letter from the CWCB was transmitted to Montezuma County regarding the Board's proposed
action for designation and approval of the Montezuma County FIS. The county was receptive to
the Board's proposed designation action, and sent an official letter requesting that the CWCB
designate and approve the floodplain information currently available to the community, A copy
of the request letter is included in the Appendix of this report,

A phone meeting was held with Tom Weaver, the County Administrator, on November 21,2000,
to explain the designation process, to review the FIRMs and to solicit comments regarding the
maps and general flooding conditions in the town, The County reported no problems with
floodplain mapping or floodplain administration, A field tour of several Montezuma County
floodplains was also conducted on November 10, 2000, No contradictory evidence to the PIS
was found during the field review,

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