Neff's Creek Floodplain Info

Debris Basin Public Meeting Materials - December 15, 2021

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

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.

Even though you may not be located in a designated flood zone you can still obtain flood insurance through the National Flood Insurance Program of which Millcreek participates. Note that flood insurance is a separate policy than your homeowners insurance policy and has a 30 day waiting period before it goes into effect for a property. Flood insurance is one of the easily accessible forms of mitigation against flood damage. We encourage you to talk with your insurance agent about a flood policy and visit to learn more. 

Learn more by visiting 

Neff’s Creek FEMA Appeal Start Information

2016 Flood Hazard study

Neff’s Creek Floodplain Map

Neffs Creek Flood Mapping Study Timeline and Next Steps graphic_6.2019
Flood Facts image DEM