Orr and Gibson creeks merge in a flood?!

This edition of City Beat is of critical importance to everyone who calls Ukiah home.

Background

In 2020, the Federal Emergency Management Agency (FEMA) began the process of updating the flood maps throughout the City of Ukiah. Flood maps are a tool that communities use to know which areas have the highest risk of flooding. They are also used by insurance companies to determine insurance rates. Naturally, the areas that are most at risk of flooding have the highest homeowners' insurance costs. Scientists at FEMA develop flood maps by plugging local weather and topographic data into a complex mathematical model to arrive at a probability of flooding in a particular geographic area. Any place with a one percent chance or higher of experiencing a flood each year is considered to have a high risk.

Preliminary results from FEMA'S 2020 modeling for Ukiah were reported to the City's engineering team in 2021. Those results indicated a radically expanded floodplain for the City of Ukiah compared to our current floodplain. In fact, the results showed that in 100-year flood (a flood so big that it has a chance of occurring only once in 100 years), Gibson and Orr Creeks, which are an average of about a quarter to a half mile apart, would merge into a virtual river! This would include several areas that were not previously identified as flood hazard areas. Specifically, all the areas between Gibson Creek and Orr Creek east of Dora Street, nearly all of the Manor Oaks Mobil Park, the majority of the Wagensellar neighborhood, the Brush Street Triangle and a great deal of the area in Talmage.

Engineering staff at the City of Ukiah does not agree with FEMA'S proposed new flood maps. We believe there are technical errors in FEMA'S modeling because it is inconceivable that a rainstorm could be so powerful and enduring that Orr and Gibson Creeks could not only flood their banks, but flood so much that they would unite to become a single river emptying into the Russian. City staff worked with FEMA staff to review the preliminary flood map and discuss contradictions between their proposed new floodplain and flood events that have been observed historically in the City. FEMA, however, did not agree with staff and stood by their findings.

So, with the city council's blessing, City staff hired two engineering firms with expertise in hydrology and a local engineer who specializes in flood elevation data. This team is analyzing FEMA'S proposed maps and the hydraulic models that supports the maps. This effort has revealed some issues with the FEMA approach. The council members agreed unanimously to get the team of consultants' opinion because property owners within this very large floodplain would see their homeowner's insurance rates increase dramatically if we allowed FEMA'S flood map to go unchallenged.

Those results indicated a radically expanded floodplain for the City of Ukiah compared to our current floodplain.

What's happening now

Consultants hired to analyze FEMA'S proposed new flood maps did in fact identify some errors with the input data that the FEMA scientists used to develop the flood maps. This is good news because it provides a solid, technical basis for appealing FEMA'S flood maps—and a technical objection is the only kind that FEMA will consider when an agency challenges its findings. It isn't their concern that higher insurance rates will affect community members.

They City has until March 15 to submit its appeal, which we fully plan to do. We will keep the public apprised of what happens next. If you are interested in viewing the proposed flood maps, they are posted on the City's website: https://cityofukiah.com/floodmaps/