This flood hazard analysis project was completed by Matrix for Eagle County, Eagle-Vail Metropolitan District and the Homeowners. Stone Creek is a beautiful small creek routed through the development as a subdivision amenity located along the Eagle-Vail Golf Course. The previous FEMA floodplain mapping was a Zone A “Approximate” delineation with an incorrect projection that did not match topography and put many homes on high terrain in the floodplain. The regulatory mapping also did not include the engineered flood bypass channel.

The Matrix study revised the floodplain mapping based on detailed hydrologic and hydraulic modeling studies. HEC-GeoRAS was used to carefully define the 100- and 500-year floodplains and the floodway. The Stone Creek floodplain mapping started at the confluence with the Eagle River and continued upstream approximately 7,700 feet, and included an additional 2,000 feet of bypass channel. The study area included 7 bridges, 7 culvert structures, and 5 split flow conditions where floodwater breaks over the bank and follows along a flow path different than the channel alignment. Once the existing conditions flood hazards were mapped, it was clear that mitigations measures could be implemented to reduce potential flooding of structures. Matrix defined five projects within the community that would take 10 structures out of the 100-year floodplain. The projects were presented to the Colorado Office of Emergency Management for possible submittal for a Hazard Mitigation Grant. Matrix, on behalf of Eagle County, prepared a grant application to FEMA, which was selected for a $240,000 Flood Mitigation Assistance Grant.