Franklin Street in Fort Collins
A Homeowner’s Process to Property Modifications in a Special Hazard Zone
Background
A Fort Collins, Colorado homeowner approached Coffey because they wanted to transform their open carport into a closed garage. The house is located in the West Vine Basin 100-year floodway, therefore the city required a floodplain analysis before the homeowner was permitted to make any changes to the property.
The Federal Emergency Management Agency (FEMA) has categorized more than 20,000 communities within the United States as a flood hazard zone. Flood hazard zones are divided into categories by given chance of flooding annually. Special hazard zones are the areas that have a 1% chance of flood each year and are also known as a 100-year floodway.
The City of Fort Collins contains twelve drainage basins, which are areas that collect precipitation and then drain off into water outlets, such as rivers, lakes and bays. The geographical location of Fort Collins makes the city vulnerable to river and stream flooding, flash flooding and urban street flooding.
West vine drainage basin. Source: Fcgov.com
The West Vine Drainage Basin is one amongst the twelve basins of the city, and totals around 2,350 acres. Only around 15% of the basin is located in Fort Collins, the rest pertains to the surrounding county of Larimer.
All flood drainage basins of Fort Collins have experienced floods caused by different factors. Floods in the West Vine Drainage typically occur during extensive rain events, where rainwater enters the irrigation ditches, and results in flood hazards in numerous locations throughout the basin.
Coffey Solution
Coffey Project Manager and Professional Engineer, Ramsey Pickard, evaluated the property using conveyance shadow analysis, which indicated that floodwaters are already flowing around the existing property structure, therefore a minor development will not alter the existing flood flow.
A no-rise certification was also performed to prove that the improvements did not raise base flood elevation, and therefore would not endanger adjacent properties.
In conclusion, the Fort Collins homeowner was approved to transform the open carport into the desired garage. See before and after images below.
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