Potential repairs planned for the Laporte Diversion Structure along the Cache La Poudre River (CLPR) initiated an investigation of the effective hydraulic model along the CLPR near Laporte, Colorado. This investigation revealed discrepancies between the crest elevation reported in the regulatory floodplain model and the actual surveyed crest elevation of the Laporte Diversion Structure. To accurately represent the flood risk for the reach near the Laporte Diversion Structure, it appears that changes to the current regulatory floodplain study via a Letter of Map Revision (LOMR) are required.  The updated hydraulic study indicates that the 1% annual chance floodplain (a.k.a. 100-year floodplain) is moderately changed while the 0.5-foot rise floodway is generally narrower than the current regulatory floodway.  The updated base flood elevations (BFE’s) associated with the 1% annual chance floodplain are higher for some properties and lower for others when compared to the current regulatory BFE’s. The LOMR report provided here describes the hydraulic study and provides a workmap illustrating the 1% annual chance floodplain, the 0.5-foot rise floodway, and the 0.2% annual chance (500-year) floodplain for the current regulatory floodplain and the updated floodplain along this reach. Flood insurance rates for properties experiencing an increase in the base flood elevation will not increase if a policy is obtained prior to the LOMR becoming effective.   

The results of this hydraulic study and the associated changes are due only to updated topographic information and survey data for the existing diversion structure and represent a “correction” to the existing floodplain mapping. Although these data and analyses are being conducted in connection with potential repairs to the Laporte Diversion Structure, the proposed project to repair the Laporte Diversion Structure has not been permitted and is not specifically included in this study. Larimer County will not permit repairs or modifications to the Laporte Diversion Structure that would produce an additional rise in the regulatory base flood elevations and/or adversely impact insurable structures.

Hydraulic Analysis - Cache La Poudre River

Larimer County has been requested to review the Letter of Map Revision (LOMR) application which will be submitted to the Federal Emergency Management Agency (FEMA) for this portion of the Poudre River.  To initiate public outreach regarding the review process for the LOMR, a public meeting will be held at the time and location below:

 

Date & Time:
Tuesday, October 15th
5:00 – 7:00 PM
*Short presentation to begin at 5:30

Location:
Larimer County Courthouse Offices Hearing Room, 1st Floor
200 West Oak Street, Fort Collins, CO 80521

Additionally, Larimer County Staff will be available to discuss the study with individual property owners at the location and hours listed below:

Individual Office Hours
Location:

Larimer County Office Building, Third Floor
200 West Oak Street, Fort Collins, CO 80521

Hours:
Wednesday, October 16th: 8:00 AM – 4:00 PM
Thursday, October 17th: 8:00 AM – 4:00 PM
Friday, October 18th: 12:00 PM – 4:00 PM
*Additional hours may be available upon request

The Public Open House is designed to provide information and allow a time for questions for Larimer County Staff. The LOMR submission is currently scheduled to be heard by the Flood Review Board at a public meeting on Friday, November 1st in the Larimer County Commissioners Hearing Room at 8:30 AM. If you have any questions, please contact the Larimer County Floodplain Administrator at (970) 498-5731 or by email.  


 

 

Cache La Poudre LOMR for La Porte Reach
Published on: 
Wednesday, October 2, 2019 - 2:45pm

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