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Gilles stands with measuring instruments in the water

From the Very Beginning

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From the very beginning, Dan Gilles has been there: on the banks of the Iowa River. When the Iowa Flood Center (IFC) legislation was signed in 2009, Gilles was there, entering his first year of graduate school at IIHR. When the Flood Center was awarded the Statewide Floodplain Mapping Project, he was there, accepting an offer to stay on after graduation to help complete the project. Today, Gilles is still here, as the IFC works on its next big venture: the Missouri River Project.

Missouri River Model of flow paths

This model of the Missouri River shows the flow paths in the channel and behind the levees after a hypothetical breach.

The Missouri River Project develops near real-time inundation maps for floodplain areas along the Missouri River, from Gavins Point, S.D., to Hamburg, Iowa. The floodplain maps provide more information on current flood conditions for Iowans living along the Missouri River, many of whom were impacted by historic flooding in 2019.

 

On a normal project, Gilles divides his time between computer modeling and gathering field data.

“That’s been a lot of fun at times,” he says, “getting out in a boat or in a kayak and using some of the survey equipment.” It can be a nice change from the office, Gilles says, but not always. “When the equipment’s not working or you get your boat stuck, it can be frustrating,” he says.

Dan Gilles and Nate Young in a boat

Dan Gilles and Nate Young taking measurements.

With Gilles’ technical expertise, 33 Iowa communities and sections of the Mississippi River have flood inundation maps that show the extent and depth of predicted floodwaters to aid in planning and decision-making before, during, and after a flood. The maps provide a graphic representation of where floodwaters will go and how deep they will be—a boon to planners, emergency managers, and business and homeowners. The maps are freely accessible on the IFC-developed Iowa Flood Information System web platform (IFIS), and more are added every year.

Outside of work, Gilles has plenty to keep him busy; he and his wife Amanda have four children: a 7-year-old, a 4-year-old, and 1-year-old twins. When the kids are otherwise occupied, Gilles likes to garden or focus on woodworking projects, a hobby he picked up just before the pandemic. He says his current project is a collection of small shelves for picture frames requested by his wife; he has also made a baby gate, a mantel, and a clock.

Gilles and the rest of the IFC team plan to have a working version of the Missouri River real-time mapping system up on IFIS by the end of this year. They are also planning to use the program for future research on the efficacy and operation of flood modeling software during a large-scale flood event.

Flooding along the railroad tracks in Fredonia

IFC Helps Solve Flooding Problems in Fredonia

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Flooding along the railroad tracks in Fredonia

Flooding along the railroad tracks in Fredonia

Each year, more towns in Iowa find themselves underwater. Many of them have small populations with limited resources, so they turn to other means for help. Robert Bright, a former city councilor from Fredonia, Iowa, contacted the Iowa Flood Center (IFC) at the University of Iowa in the summer of 2019 searching for assistance. Fredonia was underwater (again), and residents wanted answers about how to reduce their flooding and manage the water coming into town.

In June, the IFC’s Dan Gilles and Associate Director Nate Young visited Fredonia to get a better understanding of the local flood impacts.

“Since it wasn’t exactly from a major river, it’s really helpful to go to these places and see where this flooding is originating from,” Gilles says.

A map showing the natural flow of the water into Fredonia

In Fredonia, it was clear that water runoff from upstream was flowing directly into and along a railroad embankment. From there, it was redirected into the town.

They took photos, pulled LiDAR data, and used GIS (geographic information system) data to get the full picture of what they were up against.

Fredonia also contacted the Louisa County engineer, Larry Roehl, who has experience with engineering projects and difficulties in the area. The clear directionality of the flash flooding they were experiencing and local analyses helped Fredonians understand what was likely causing the flooding.

The flood center provided technical expertise to make a scientific assessment and compile a report. The final report offered solutions to the city’s flooding problems and identified next steps for the community to pursue. Fredonia used the report in an application for flood recovery and mitigation funding, which resulted in more than $100,000 for the community’s flood mitigation projects.

Gilles says in many cases, small towns such as Fredonia need a limited study and report to apply for flood assistance, which IFC can sometimes provide free of charge depending on the situation.

Updated Flood Inundation Maps Available for Waverly

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Inundation Maps Released for Waverly

The Iowa Flood Center has released newly updated flood inundation maps for the community of Waverly. These maps are accessible on the Internet through the Iowa Flood Information System (IFIS), an interactive Google Maps-based online application. The inundation maps are frequently used by local authorities for planning and real-time flood mitigation, but are also useful for homeowners, business owners, and others.Waverly Flood Maps

The City of Waverly, perched on the banks of the Cedar River, is prone to seasonal flooding. Like many Iowa communities, Waverly experienced severe flooding in 2008 that inundated the downtown, including city offices.

An unusually wet spring in 2013 brought additional flooding to residential areas of the city and reinforced the community’s need for tools to better understand flood risks.

The Iowa Flood Center, created in 2009, was charged with developing inundation maps for those communities most affected by the floods of 2008. IFC Water Resources Engineer Dan Gilles says that the maps creation process begins with data collection. Typically, the team will collect measurements of the river bed and any structures in the floodplain that affect how the river flows. These structures could include dams, bridges, levees, or even buildings. All of these data are used to create a computer model of the river and surrounding floodplain. In this particular case, the team was able to make use of an existing FEMA flood model and make some minor updates. Once a satisfactory model is developed, the team then selects the flow simulation scenarios, conducts post-processing of simulation results, gathers and applies feedback from the city and county, and finally releases the maps.

This is the second release of maps for the Waverly community, which have been revised following additional feedback from the city. “After receiving some valuable data from the City of Waverly, we chose to process some of the high flow simulation results differently to reflect their observations during the 2013 flooding event,” Gilles says.

In addition, the city’s recent installation of an inflatable dam, which can be adjusted to regulate the upstream pool height, significantly altered the model. Gilles explains that while the U.S. Geological Survey’s gauges use the river’s stage to estimate flow, the new dam disrupts that relationship and has caused the USGS to deploy different techniques to estimate flow through Waverly. These most recent revisions more accurately reflect the relationship between flow and inundation extent on the maps.

Waverly City Administrator Phil Jones described IFIS as a great way to see both real-time precipitation and river information. He adds that during last May’s flooding, the system allowed city officials to see the rainfall in the upper part of the watershed and the changes in stream levels as the high water flowed south. They were able to then apply that data to the inundation maps to get an idea of the potential impact on Waverly.

The IFC team has created an ever-expanding library of inundation maps; currently maps exist for 12 Iowa communities. The IFC continues to improve these maps in response to feedback from local officials and new flood mitigation systems installed by these communities.

MEDIA CONTACT: Jackie Stolze, Iowa Flood Center, 319-335-6410, jackie-stolze@uiowa.edu