WSP05314

• File Number: 5000.375
• Description: Flood Protection Section - Alamosa - Rio Grande Flood
• State: CO
• Basin: Rio Grande
• Water Division: 3
• Date: 10/31/1985
• Author: Muller Engineering C
• Title: Reconnaissance Report - Rio Grande Levee System at Alamosa - Prepared for City of Alamosa and Alamosa County - In Cooperation with CWCB
• Water Supply Pro - Doc Type: Report/Study

0018-'5

Building damages were estimated using the values listed below for
replacement costs on buildings typical of those within the floodplain.
The source of the costs was Mr. Fritz Blake of the COE. Replacement
values of structures were estimated as follows:

Residential Building .......... $50,000
Commerci al Buil di ng ........... $40,000
Mobile Homes .................. $18~OOO

Val ues of buildi ng contents are expressed as a percentage of the
building's replacement value and were estimated to be as follows:

Residential Building .......... 45%
Commercial Building ........... 60%
Mobile Homes .................. 40%

Damage curves prepared by the Federal Insurance Administration were
used to determine percent damage to buildings and contents as a
function of depth of inundation. On an average basis, depths to the
first floor were estimated to be as follows:

Residential Building .......... 1.5 ft.
Commercial Building ........... 0.5 ft.
Mobile Homes ..................2.0 ft.

Costs for miscellaneous damages to public facilities and for flood
fi ght act i vit i es were ext rapol ated from the report prepared by the
State Damage Survey Team on August 8, 1985. The costs for the 1985
flood (estimated as a 10-year runoff) totaled approximately $315,000
for the City oJ Alamosa and the County combined. These costs were
extrapolated to the following values for other recurrence intervals:

Flood Event

Miscellaneous
Damages

IO-year .............. $315,000
25-year .............. $800,000
50-year............ $1,000,000
100-year ............ $1,200,000
500-year ............ $2,000,000

Using the cost parameters, flood damages were estimated for a range of
flood events through the 500-year frequency flood. Table 4 shows the
estimated flood damages, as well as the approximate annual risk the
community now assumes with the current levee system. Adding on the
estimated premium costs for flood insurance coverage, approximately
$100,000, the Alamosa area is accruing an average public and private
flood damage of $1,047,700 per year.

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