Neff's Creek Floodplain

Flood Maps for Neff’s Creek Are Changing (updated: 3/16/2018)

The Utah Division of Emergency Management (DEM), the Federal Emergency Management Agency (FEMA), Millcreek City, and Salt Lake County are working together to update flood maps for the Jordan Watershed, which includes Neff’s Creek, located in Millcreek’s Olympus Cove.

The timeline has shifted since the original guidance documents below were created. By early fall of 2018, FEMA anticipates releasing a preliminary (draft) Flood Insurance Rate Map (FIRM) estimated to become effective in 2019. The work maps provide updated flood risk information for Olympus Cove and designate the floodplain along Neff’s Creek as an active alluvial fan. An alluvial fan is a fan-shaped area where rivers and streams deposit silt, sand, gravel, boulders and woody debris over time. Active alluvial fans are prone to sudden, unpredictable flood events.

On the new work maps, Olympus Cove is categorized using three different flood designations for active alluvial fans: Zone A (higher risk), Zone AO (moderate risk), and Shaded Zone X (lower risk). The Zone A areas, predominantly located highest (uphill) on the fan, could experience the highest water levels (depths) and water speeds (velocities) during a flood. The Zone AO areas are defined by flooding with lower water depths and velocities. The Shaded Zone X areas have the lowest alluvial fan hazards. For properties in Zone A and Zone AO, the owners will be required to buy flood insurance when the FIRM becomes effective, if the structures are financed by federally backed mortgages. Although properties in the Shaded Zone X areas will not be subject to federal flood insurance requirements, flood insurance is strongly recommended for structures in these areas, as alluvial fan flooding is unpredictable.

In May 2016, representatives from DEM, FEMA and Salt Lake County hosted two community meetings for Olympus Cove residents to preview the draft work maps and learn about upcoming changes.

Please see the following fact sheets and Frequently Asked Questions: