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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Mr. Greg Sparks
Page 2

improvements and other development within the adopted regulatory
floodway that would result in any increase in the base (lOO-year)
flood elevations (BFES). We are concerned the fill at the
Riverwood Estates Subdivision is increasing BFEs and creating
unnecessary flood hazards. As stated in your December 19, 1985
letter, the channel work (channel straightening, sediment removal,
vegetation clearance, and construction and/or rehabilitation of
levees) may not be completed on the Rio Grande River until 1990.
However, mitigative measures must be undertaken, immediately, to
restore the flood carrying capacity of the river and to protect
structures constructed inappropriately in the floodway at the
Riverwood Estates Subdivision.

In addition, it is important the FIRMs and PBTHs reflect physical
changes affecting flooding conditions so risk premium flood
insurance rates and flood plain management requirements will be
based upon current data. Therefore, if any of the channel work
mentioned above changes the flood plain, the City must submit
technical data to FEMA substantiating the change. FEMA provides
procedures for flood plain changes which are enclosed.

Lastly, in order for the City to remain compliant with the NFIP
and eligible for flood insurance, we request the following actions
be taken.

1) Adopt the floodway and base (lOO-year) flood
elevation. as described in the Flood Insurance Study
(FIS) for Alamosa County for any annexed areas.

2) Provide FEMA a copy of the City's amended ordinance.

3) Plot the annnexed areas on the City's FIRM and FBFM.
(We will try to locate the work maps developed by the
Corps of Engineers for the FIS. These maps will provide
a more workable scale.)

4) Plot the floodway from the Alamosa County ~BFH on
the City's FBFM for any annexed areas.

5) Take mitigative structural measures to compensate
for lost conveyance due to fill in the floodway at the
Riverwood Bstates Subdivision and provide VEMA, Region
8, technical data substantiating the measures, as
outlined in the procedures.

6) Deny building permits within the floodway unless
improvements are provided to restore conveyance lost by