FLOOD06725

• County: Dolores
• Community: Dove Creek
• Basin: San Juan/Dolores
• Title: Floodplain Information Report
• Date: 9/1/2000
• Prepared For: Dove Creek
• Prepared By: CWCB
• Contract/PO #: &&
• Floodplain - Doc Type: Floodplain Report/Masterplan

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ENGINEERING METHODS

Hvdrolol!ic Analvsis
The Dove Creek FHBM presents 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 lOa-year flood-flow
values. However, due to a lack of information, these equations are not available for the Western
San Juan River Subregion. Therefore, approximation methods developed by the USGS were
used in this analysis.

The USGS regional regression equation methodology is fully described in USGS Water
Resources Investigations Report 99-4190, entitled "Analysis of the Magnitude and Frequency of
Floods in Colorado". The Southwest Region equation is used for streams in the San Juan River
Basin within Colorado, with drainage basin areas between 5.5 and 988 square miles. The USGS
regression equation is:

Equation 1
Regional Regression Equations for Dove Creek

QulO = 118.4(A)o.1l5

(Only for drainage areas between 5.5 and 988 square miles)

For Equation 1, the QIOO is the lOa-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 as shown next to the equation.

The lOa-year flow for Dove Creek at the downstream Town Limits were estimated by utilizing
the regional regression equations presented in Equation 1. Table 1 presents lOa-year flow
estimate for this location.

s Imate ISC ar2es or ove ree
lOO-year
Drainage Discharge
FloodiDl! Source Location Area (mi') (cfs)
Dove Creek at d/s Town of Dove Creek corporate boundary 8.51 550

Ef

Table 1
d D' h ~ D

C k

Dove Creek should regulate the approximate floodplains on a case-by-case basis. FEMA
requires that a detailed floodplain analysis must be performed by a professional engineer and
submitted by the developer or development proponent for development projects involving more 5
acres or more than 50 units (whichever is more restrictive).

Hvdraulic Analvsis
Hydraulic methods used for the approximate floodplain delineations shown on the Dove Creek
FHBM panels are not available or have not been documented by FEMA. For future studies, an

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