Monday, March 8, 2021


Floodplain Maps Updated for Maxwell, Arbuckle & Williams

Over three years ago FEMA (Federal Emergency Management Agency) initiated the process of “Map Moderization” to update the Colusa County National Flood Insurance Program (NFIP) Flood Maps. Supervisor Denise Carter has been leading the effort on behalf of the County and organized the initial meeting with FEMA, interested public and staff to discuss concerns that existing maps in Arbuckle, Williams and Maxwell were not reflective of actual flood flow patterns. “People were paying for flood insurance when they didn’t need to”, said Carter and local funds were not available to conduct the extensive engineering study to get the maps changed. FEMA Region IX Engineer Kathy Schaefer, P.E. CFM, agreed with local concerns and found federal funding to do a two-dimensional hydraulic modeling study for the Arbuckle, Williams and Maxwell communities.

Schaefer along with FEMA Region IX NFIP Planner, Zing Liu, and cooperating technical partner ,CH2MHILL project manager Bill Fox, P.E., L.S. reviewed the study findings with the Colusa County Board of Supervisors on Tuesday, December 10th.

The updated maps now reflect a significant reduction of homes mapped in a flood zone, particularly in Arbuckle. Supervisor Kim Vann commented after the presentation that the updated maps will make a huge difference for Colusa County property owners. “Our last update was in 2003 with blanket 1-D maps with no funding to challenge,” said Vann. “Thank you for finding the funding to provide some real on-the-ground data,” she said to Schaefer and her team.

During the study FEMA and Department of Water Resources (DWR) worked to acquire the LIDAR data (accurate topographic data), conducted field surveys, and updated the hydrology to recognize that the Tehama Colusa Canal and I-5 are engineered structures that impede flow. They then built two-dimensional hydraulic models to conduct floodplain evaluations, produce preliminary floodplain delineations (Base Flood Elevations-BFE), and develop preliminary floodplain workmaps.

Arbuckle Rural Fire Chief Casey Cox commented that he appreciated the thorough and careful updates that the board had sought for the county. “Speculation makes it tough. I know of some families who are letting go of homes because the flood insurance is the highest it has ever been,” he said.

Schaefer explained that the board can elect to adopt the proposed maps as best available data, there would be a 90 day appeal period during the map production. Upon adoption by the Board of Supervisors, the maps may be used by affected property owners. She estimated that the letter of final determination of the maps will likely take up to one and a half years to complete.

Supervisor Carter added, “We appreciate and thank FEMA, its partners and in particular Kathy Schaefer for their willingness to work with us. This is just the first step in remapping of the County. As we move to other parts of the County, particularly along the Sacramento River, we will have more significant issues to address.” FEMA plans to return in early 2014 to continue the process of revising the remaining Colusa County NFIP flood maps







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