With a 5-0 vote, the Wahpeton Flood Protection Committee approved recommending submission of new geometric data for the Otter Tail and Bois de Sioux rivers to FEMA.
Mike Bassingthwaite, eastern regional vice president and Wahpeton office manager of Interstate Engineering, appeared before the committee Monday, Sept. 9. He presented information on the final findings of FEMA’s flood plain mapping.
In 2017, the U.S. Army Corps of Engineers completed their portion of a study on local flood protection and diversion systems, Daily News previously reported. This information was submitted to FEMA so the levees could be certified.
“As the flood control systems finally got completed in the twin towns, they were going to complete their FEMA mapping,” Bassingthwaite said. “The areas of the cities that were behind the protective levees would be out of flood insurance zone, with the anticipation that those individuals would no longer have to pay the high premiums for flood insurance.”
Concerns were raised by the initial maps, Bassingthwaite said. The 100-year base flood elevation, which insurance rate maps are based on, was higher than what the Corps wanted for freeboard on the levees.
“The idea was that the top of the levees should be three feet fighter than what the base flood elevation is,” Bassingthwaite said.
Base flood elevations are decided by two components: the geometry of the river and the countryside (basically the size of the river and floodplain itself) and hydrology (how much water in a 100-year theoretical flood would be placed in that river system).
Interstate started looking at the geometry first, Bassingthwaite said, because they knew the Corps was looking at antiquated geometric data.
“There is a significant difference for what the Corps was proposing for base flood elevations versus what we though it should be based on the geometry,” Bassingthwaite said.
When it came to the Bois de Sioux, Interstate was not able to find enough changes in the geometric data the Corps had versus what it surveyed of the river. The data doesn’t show much, if any, change from the Corps’ information about immediately upstream of Wahpeton and Breckenridge, Minnesota.
Interstate knew they would be short on time when they started gathering data, Bassingthwaite said.
“To be able to accomplish this, we thought we would have had to have this done by now,” he continued. “But the Corps and FEMA have pushed back the establishment of these maps several times now. Now they’ve actually started the appeal period.”
The clock is ticking on a 90-day window to appeal current Corps maps, Bassingthwaite said.
“What we’re proposing to submit to FEMA to change the geometry of the countryside, provide those benefits for the countryside and it is what it is,” Bassingthwaite said.
Bassingthwaite previously presented his information to the Breckenridge City Council. He is scheduled to update the board of commissioners in Wilkin County, Minnesota, and Richland County, North Dakota.
Wahpeton’s Flood Protection Committee includes the four members of the city Public Works and Safety Committee and Mayor Steve Dale. Councilwoman Renelle Bertsch, 2nd Ward, also attended the meeting.
The next Wahpeton City Council meeting is scheduled for 5 p.m. Monday, Sept. 16 at City Hall, 1900 Fourth St. N. in Wahpeton.