WHAT IS THE ONE-HUNDRED YEAR FLOOD?

The one-hundred year flood gets a lot of attention, but its name is a bit misleading. It simply refers to a flood that has a one percent or greater chance of occurring within any given year. It is increasingly referred to as the Base Flood to avoid confusion. The area expected to be inundated by the Base Flood is known as the Special Flood Hazard Area (SFHA). Some sites located within the mapped SFHA may actually be affected by a smaller flooding event. It is even possible to be inundated by multiple ‘one-hundred year floods’ within the same year, although statistically unlikely. It is also important to note that FEMA estimates about 20 to 30 percent of floods occur outside of the SFHA.

In 1968 Congress made FEMA responsible for the creation of flood maps nationwide. These maps are used to regulate development by local jurisdictions and to assess flood risk by property owners, insurance companies and lenders. Our currently adopted maps are based on FEMA’s original maps for our community. The Willamette and Amazon Rivers have had detailed studies created by FEMA for them.

This page has links to a variety of flood information. Some are regarding flooding risk, our adopted maps, flood insurance and facts pertinent to construction within the floodplain. This page also has important links to pages on how to prepare for a flood and what to do after a flood.

FLOOD INFORMATION IS AVAILABLE TO THE PUBLIC

Public Works Engineering staff at the Permit & Information Center provide information on floodplain issues to the public. Free services include determining whether a property is within the floodplain or floodway, the Flood Insurance Rate Map (FIRM) zone for a specific property, and the Base Flood Elevation for the property if it is available. 

The City of Eugene retains copies of determinations from FEMA for those sites that have been removed from the floodplain. These determinations are collectively known as Letters of Map Changes (LOMCs) and are specifically Letters of Map Amendments (LOMAs) and Letters of Map Revisions (LOMRs). Elevation Certificates required for new construction are retained at the Permit & Information Center and are available as well.