FLOOD03452

• County: San Miguel
• Community: Telluride and Sawpit
• Basin: San Juan/Dolores
• Title: Hydrology Addendum San Miguel County And Incorporated Areas
• Date: 11/1/2000
• Prepared For: County of San Miguel
• Prepared By: CWCB
• Floodplain - Doc Type: Floodplain Report/Masterplan

I.
.
.
I.
.
.
.
.
I.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.

I:
.
.
.
.
I.
i.
.
I.
.
.
.
.
.
.
.

ENGINEERING METHODS

Hvdroloeic Analvsis
The San Miguel County F1S presents detailed and approximate floodplain delineations.
Hydrologic information used for the FEMA approximate floodplain delineations are not available
or were not documented by FEMA, The CWCB has developed acceptable hydrologic
information for undeveloped basins using regional regression methodologies for computing 100-
year flood-flow values,

The CWCB methodology is fully described in a publication by the CWCB entitled "Guidelines
for Determining 100-year Flood Flows for Approximate Floodplains in Colorado". The Dolores
River Subregion (DLR-I) was used for streams in the Dolores River basin, including the San
Miguel River sub-basin, The CWCB equation for the Dolores River subregion is as follows:

Equation 1
Regional Regression Equations for San Miguel County

QUMl = 213.8(A)o,601

(Only for drainage areas between 2 and 1080 square miles)

For the Equation I, the QIOO is the 100-year peak flow in cubic feet per second, and A is the
upstream (contributing) drainage area in square miles, The regression equation is only valid for
the range of drainage areas indicated,

The lOO-year discharge for approximate floodplains in San Miguel County were estimated by
utilizing the regional regression equations shown above, The estimated lOO-year peak
discharges are shown in Table 2,

5