FLOOD10104

• County: Alamosa
• Community: Alamosa
• Stream Name: Rio Grande
• Basin: Rio Grande
• Title: Riverwood Estates Subdivision Rio Grande Floodway Evaluation
• Date: 4/3/1987
• Prepared For: Alamosa
• Prepared By: Muller Engineering Company, Inc.
• Floodplain - Doc Type: Floodplain Report/Masterplan

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3. River cleared and maintained vegetation free and major
sandbars removed ('n'=0.03).

The computed flood profile for the 1985 river condition compared well
with the FIS at the downstream and upstream study limits, an
indication of the compatibility of the models.

The model showed that efforts taken to clean the river of vegetation
and sandbars was very effective in lowering the flood profiles,
conditi ons 2 and 3, above. Cl eani ng woul d lower the profil es 1- to
2-feet. The model also showed that the calculated average flow
velocities are relatively low which means river backwater effects are
high and thus changes downstream have a significant impact upstream.

River Cross Section Surveys (1986)

For this study, City crews obtained surveys of four river cross
secti ons in the area of Ri verwood Estates. I n May, 1986, Secti ons
28.8 and 29.0 were surveyed. In September, 1986, Sections 28.4 and
29.5 were surveyed. Only the main river channel area of each section
was surveyed.

The datum for these surveys was not identified by the City. This
study has presumed the datum is the same for the 1986, 1985 and FIS
surveys. This should be confirmed by the City.

The surveyed cross sections are plotted in Figures 1-3. The plots
show that the sections taken from the FIS study maps and the surveys
in 1985 and 1986 compare well in the area where no changes were made.

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