RED OAK, Iowa — The “office” for Dan Gilles and Tony Loeser was the East Nishnabotna River.
The engineers with the Iowa Flood Center were in Red Oak Wednesday morning in an effort to map where and when areas will flood. They measured the bathymetry — underwater topography, measuring depth and land structure — along 4 miles of the river outside the Montgomery County city.
The effort is an Iowa Flood Information System project.
“When the (National) Weather Service says, ‘The river stage is at 20 feet,’ people upstream and downstream of their measuring point don’t necessarily know what that means for them,” Gilles said. “We want to help with that.”
Just off Iowa Highway 48 west of the city, Loeser assisted Gilles as he loaded up a kayak with two key pieces of equipment — a sonar depth-testing device that measures depth by bouncing sound waves off the bottom; and a global-positioning device to measure latitude, longitude and elevation.
Loeser fired up a laptop while sitting on the shore as Gilles waded into the water, prepping the kayak. Watercraft and equipment ready, Gilles set off. The engineer paddled a zigzag route in an effort to measure as much area as possible.
Loeser and Gilles explained that the underwater readings were necessary because existing Iowa topography data show rivers as smooth, with no depth readings. The bathymetry and topography data will be combined, and engineers will create computer models and maps that’ll show what land will flood at a variety of river levels.
The maps will help users visualize the potential extent of flooding, with the information assisting in planning and mitigation decisions. Loeser said it could help homeowners, business owners and others see how predicted flood levels might affect their property.
The Red Oak East Nishnabotna maps will be available to citizens at ifis.iowafloodcenter.org later this year or early next year, Gilles said. River depth data will be available online in a few days.
“It’s really important in that people will have access to more information,” Loeser said. “These maps will allow people to assess their own risk.”
The last major flooding in Red Oak occurred in 2007 and 2008, according to Red Oak City Administrator Brad Wright.
Loeser said the maps will also help emergency management agencies determine the need for road closures and evacuations.
In addition to testing water depth in Red Oak, Gilles and Loeser also walked the levee that protects Red Oak from the river, gathering elevation data. That information will be used for flood center work and also be passed on to a consulting firm doing work for the City of Red Oak as it works to meet Federal Emergency Management Agency requirements for levee accreditation.
“We’re trying to hit towns that have historically had flood issues,” Gilles said.