FLOOD00067

• County: Alamosa
• Community: Alamosa
• Stream Name: Rio Grande River
• Title: Flood Control Status Report for Alamosa County and City
• Date: 7/1/1987
• Prepared For: Alamosa County
• Prepared By: CWCB
• Floodplain - Doc Type: Project

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The MUller report hydraulic evaluations indicated that a
cleared river system could pass the 100-year flood at a profile
approximately 2-feet lower than the comparable flood profile
with the river choked with vegetation and large accumulations
of river sediment. Clearing the river channel on a regular
basis would provide significant economic benefits to the
community in terms of maintaining the levee system capacity.
Improvements to the levee system were identified that, if
implemented, would upgrade the integri ty and capacity of the
system to federal standards and criteria. Improvements
included raising and widening the levees. providing riprap
armor protection, reducing seepage under and through the
levees, providing access control along the top of the levees
and constructing new tieback levees northwest of the City for
right and left bank levee systems.

Initial estimates of construction costs for the conceptual
improvements totaled approximately $6.4 million, including
construction, contingencies and engineering. Based upon the
cost estimates of flood damages and constructing the
improvements, as Qptlined in the report, the improvements were
rated economically justifiable as represented by an approximate
benefit/cost ratio ranging from 2.5 to 3.

The Muller Engineering report
the potential flood losses in
inundation of the community.
to determine an es t ima te of
flood risk.

contained an economic analysis of
the area resulting from the flood
The purpose of this analysis was
the cost of the average annual

The majority of the damages would occur to private and pUblic
properties once the capacity of the current system was
exceeded, at about the 25-year flood event. Figure 1 shows the
damage curve of estimated flood losses for each flood frequency.

Also shown on Figure 1 and Table 2 are the damage curve and
annual risk to the community with an improved levees system
capable of passing the 100-year flood through the community, as
well as part of the 500-year flood. The annual flood risk
after improvements would be $63,315.

The report indicated that the improved levee system could
provide a reduction in the annual risk and thus a benefit to
the Community of approximately $984,385. The report also
stated that with funding avai lable, first priority and
immediate action should be taken to upgrade the East Alamosa
levee between U.S. 160 and the railroad.

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