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City staff, state officials warn draft floodplain maps could expand pluvial flood zones; Hutchinson plans preemptive projects
Summary
Hutchinson staff and Kansas mapping officials told the council that draft floodplain maps now under development may substantially expand areas shown as at risk from surface (pluvial) flooding. City engineers outlined near-term self-perform projects and requested resources to validate consultant models and pursue mitigation grants.
City engineering staff and state floodplain mapping officials briefed the Hutchinson City Council July 15 on a statewide floodplain update that may add new surface-flooding areas for the city and on steps the city can take now to reduce mapped risk.
City Engineer Evan Patterson said draft maps the state is preparing show materially more area in the floodplain than the 2021 maps and urged validation of the consultant models. “The previews we've seen are as if someone had thrown a tomato at the old map, and the splatter was the areas that are now in the floodplain,” Patterson told the council.
Joanna Wolf, floodplain mapping coordinator at the Kansas Department of Agriculture Division of Water Resources, said the mapping project started in 2022 and that a community review meeting is expected in late August or September; final federal insurance maps could be effective as early as 2027, she said. The maps use updated rainfall data and higher-resolution terrain information that can change which parcels are labeled at the 1% annual-chance flood level.
Patterson and staff described a short list of city projects they can self-perform quickly — mostly grading and small detention basins on city-owned land — that could reduce the amount of area appearing in the final maps if those changes are included in the model before publication. He said staff will coordinate with the state and the consultant to ensure work is represented in the hydrologic/hydraulic models.
Consultants on the call urged model review. Alonzo Tavar, an engineer who has worked on similar model reviews in the Kansas City region, said independent validation of inputs and calibration points is routine and important to avoid overstatement of risk. The city also plans to pursue federal Hazard Mitigation Assistance and to revisit larger projects, including Cow Creek work and a State Fair detention basin, using updated benefit-cost analyses if the floodplain expands.
What residents should know: Patterson said new maps are published online for public review; homeowners who appear in a new flood zone can pursue a Letter of Map Amendment or Letter of Map Revision using survey or elevation documentation. He warned that mortgage lenders may still require flood insurance while appeals or map changes are processed.
Council direction: staff asked for permission to validate the consultant models, identify short self-perform projects on city-owned land, and seek federal and state mitigation funding; council did not oppose those steps and asked staff to return with a prioritized work program for council review.
