City consultant: FEMA floodplain revision would add 19 structures; owners can pursue surveys to contest

A consultant hired by the City of Flandreau told the council Monday that FEMA’s proposed floodplain revisions would newly place 19 structures inside the 100-year floodplain and that individual property surveys would be the most viable path to remove buildings from the map.

Shane (floodplain consultant) told the council he reviewed FEMA’s model, cross sections and LiDAR-derived elevations and identified 19 structures in the new footprint — two commercial buildings (Mad Mary’s and The Spot), two public properties with outbuildings and about 15 private residences along Industrial Park Drive to Crescent Street. He said a previously issued LOMA removed the Tractor Supply building from the floodplain and that building appears unlikely to return under the new map.

The consultant said his calculation of the controlling flow was about 34,128 cubic feet per second; FEMA used a higher flow figure — about 47,296 cubic feet per second — roughly a 30% difference. Shane said FEMA told the city its result remains “within the allowable brackets” and that FEMA’s approach is intentionally conservative. He cautioned the council that pursuing a formal technical challenge (the federal scientific resolution panel process described in FEMA materials) would be costly and might not change FEMA’s determination.

Why it matters: being included in the regulatory 100-year floodplain can trigger mandatory flood insurance for properties with federally backed mortgages and can affect permitting. Shane told the council that property owners or the city can provide elevation certificates or site surveys showing the lowest adjacent grade to seek removal from the floodplain.

Supporting details: Shane recommended property-level elevation surveys if owners want to attempt removal. He estimated a targeted elevation survey would likely start around $1,500 per property and rise with property size or complexity, while a mortgage-style survey could be closer to $2,000; he noted doing multiple properties on a single survey trip would lower per-parcel costs. Shane also described technical reasons the FEMA model produced a higher flow near the Highway 32 bridge — including differences in historical cross-section data and bridge replacement — and said LiDAR accuracy and “shadow” areas can cause the model to place a small corner of the public school inside the new line.

Council next steps and timeline: council members discussed notifying affected property owners and whether the city should coordinate a group survey. Mayor Dan indicated staff would provide standardized notification letters and follow the normal ordinance updates required to reflect new map boundaries when issuing permits. The packet includes the consultant’s full memo and FEMA’s response letter; Shane said the city can direct property owners to pursue elevation certificates or a coordinated, city-assisted survey if the council so chooses.

Quotes: “We came up with 34,128 cubic feet per second, and the FEMA flow was considerably higher at 47,296,” Shane said, describing his review. “They’re being extra conservative, which I guess is fine unless you’re the person who’s paying flood insurance.”

Ending: The council will make the consultant’s packet available to property owners and will hold a public meeting on the related water/sewer project and other items March 24; Shane said property owners who want to pursue removal should begin by obtaining an elevation certificate or hiring a surveyor to confirm the lowest adjacent grade.