The 100 year Floodplain delineation was provided by the Federal Emergency Management Agency (FEMA) and is illustrated as-is, for all of Larimer County (not just the Big Thompson River and the Cache La Poudre River). The floodplain is delineated by FEMA for the purpose of flood insurance determination, and only implies that area affected will contain some level of standing or moving water.
Though the designated FEMA 100 year floodplain is illustrated for all reaches in Larimer County, (ie. Box Elder Creek, Big Thompson, Cache La Poudre) the waterways of primary flooding concern are the Big Thompson and Cache La Poudre River.
This mapping is intended for planning purposes only and may not be representative of the actual flooding event. Flooding may deviate from the FEMA delineated boundary based on field conditions, weather, and changes in hydraulic flow (ie. Culverts become blocked with debris and are not functioning as designed).