FLOOD06837

• County: Alamosa
• Community: Alamosa
• Stream Name: Rio Grande
• Basin: Rio Grande
• Title: Master Drainage Plan Alamosa
• Date: 3/1/1982
• Prepared For: Alamosa
• Prepared By: McCarty-Hurst
• Floodplain - Doc Type: Floodplain Report/Masterplan

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The manager of the Alamosa Inn has had stormwater in the easterly
units and feels inadequate grading is the reason for the lack of
drainage. The owner of the Pizza House on West Main Avenue has ob-
served flooding at the Alamosa Inn, Haynies' Auto Parts, and other
places within the city. She attributes most of the flooding prob-
lems to inadequately-sized storm sewers.

During the field investigations, attempts were made to supplement the
mapping by using photo documentation, relative elevations between
points, andothermiscellaneous notations.

A local real-estate agent was interviewed to obtain characteristic
price ranges of various properties in the study area.

B. HYDROLOGY

The study area was divided into basins based upon natural and man-
made features which affect natural drainage patterns (Figure 2 shows
the basins). Basin delineations were prepared from the available
mapping and confirmed by site visits.

The areas west and northwest of the city are not tributary to most of
the existing development in the city. Drainage northwest of the city
is toward the Rio Grande River. Small portions drain towards U.S.
Highway 160/285. The area west of the city, south of the railroad
and U.S. Highway 160/285, drains to the southwest or does not drain
at all due to the natural local depressions (sumps) in the area.

Many of the eight designated basins are less than 200 acres in size.
Appropriately, the Rational Formula was selected as the best hydro-
logic methodology for this project. The Rational Formula is used
to determine the amount of stormwater runoff at design point loca-
tions for the various storm frequencies. This method is an accepted
procedure for calculation of discharges in small, local drainage

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