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Screenshot of Hazus on IFIS.

Modeling the Costs of Flood Damage

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In May 2017, the Iowa Flood Information System (IFIS) added data to the web from HAZUS, which allows users to estimate the cost of flood damages to buildings and other structures in various flooding scenarios. HAZUS data is currently available for seven Iowa communities, and Iowa Flood Center (IFC) researchers are working to expand the tool to cover the entire state.

HAZUS, developed and distributed by the Federal Emergency Management Agency (FEMA), is a multi- natural hazard analysis tool. FEMA first released HAZUS in 1997, and its most recent version, HAZUS 4.0, is capable of analyzing floods, hurricanes, tsunamis, and earthquakes. The web tool models the effects that natural hazards of various intensities can have on buildings and other structures in a given area, and then quantifies the total damage in dollars.

In 2017, IIHR Research Engineer and Assistant Professor Ibrahim Demir and graduate research assistant Enes Yildirim integrated HAZUS datasets into IFIS. Yildirim extracted the flood related datasets from HAZUS, including census data on demographics, buildings, structural content, and the number of schools and critical structures near rivers, and integrated it into existing IFIS flood maps. Yildirim also analyzed how emergency responders could use HAZUS and created a user-friendly web-design that would be intuitive and easy for decision-makers and the public to use.

How does HAZUS work on IFIS?

Currently, IFIS provides flood loss and damage estimation for 12 communities: Cedar Rapids, Cedar Falls,  Des Moines, Fort Dodge, Iowa City, Independence, Kalona, Monticello, Ottumwa, Rock Rapids, Rock Valley, and Waterloo. To calculate flood damage for one of these communities, users can hover their cursor over the “Flood Maps” tab and find their community under the “Flood Map Scenarios for Communities” button. Then, after clicking on the “Damage Estimate” button, users can toggle the “Flood Map Controller” to model different scenarios.

For example, users can select Iowa City, simulate a 30-foot stage flood, and receive a total damage estimate of $19 million, which factors in the number of buildings damaged and the cost of the damage to their structure and content. Users can also click on individual buildings in the flooded area to access estimates of content and structural damage to those buildings. Demir says that level of detail will be useful for decision-makers and ordinary citizens who need to evaluate scenarios specific to them. Demir and Yildirim plan to add additional analysis layers that will include the number of schools, critical structures, and emergency centers affected in the damage estimate. Demir and his team will add the additional layers after bringing the current level of analysis to all Iowa communities.

Mapping the Future

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The Iowa Floodplain Mapping team.

The Iowa Floodplain Mapping team.

Accurate scientific information will be one of Iowa’s best defenses against future floods, says Iowa Flood Center Associate Director Nathan Young.

He is leading an effort to update floodplain maps for 85 of Iowa’s 99 counties. Young, who is also an IIHR research engineer, says that the new floodplain maps provide a direct and easy-to-understand way to communicate flood risk to Iowans.

The IFC, located at the University of Iowa’s IIHR—Hydroscience & Engineering, is about one year into the four-year Iowa Floodplain Mapping Project, funded with $10 million from the U.S. Department of Housing and Urban Development. Working closely with the Iowa Department of Natural Resources (DNR), the IFC will develop floodplain maps for the Iowa counties that were declared federal disaster areas after the 2008 floods. Some or all of the maps will eventually be adopted by the Federal Emergency Management Agency (FEMA) as regulatory maps.

“We’re excited to partner with the DNR on this important statewide project,” Young says. “These maps will provide Iowans with new information concerning flood risk in their own communities, so they are empowered to make informed land use and land management decisions.”

DNR Floodplain Mapping Coordinator Scott Ralston agrees. “We look forward to delivering quality flood hazard data to Iowans to increase public awareness and help protect life and property into the future.”

A Herculean Task

The scope of the project is huge. IFC researchers are mapping all streams draining one square mile or more. To accomplish this, they rely heavily on statewide LiDAR (laser radar) data recently collected by the DNR. LiDAR is a remote-sensing technology that researchers use to develop digital elevation models of the land surface. The availability of LiDAR was a major reason mapping funds were allocated to the state, Young says. “LiDAR data allow for more precise delineation of floodplain boundaries.” With these data, the team will be able to describe Iowa’s river and stream networks, develop computer-based flood simulations, and delineate floodplains with reasonable accuracy.

The project involves digitizing the state’s stream network, performing hydraulic and hydrologic analyses, and using the results to create maps. After a successful pilot project in Poweshiek County, the team turned to the statewide effort. The extent of the project requires the development of innovative, efficient new floodplain mapping tools, and the new data products will offer value beyond the mapping projects.

“Scaling the project up to the entire state and developing and managing such a large volume of data is daunting,” Young says. “We have hired a large number of engineers, GIS staff, and students dedicated specifically to the project. Our partnership with the DNR has also been a great help in that regard.”

“It has been rewarding to utilize the technical expertise of the IFC in the areas of hydrology, river hydraulics, and state-of-the-art GIS technology,” Ralston says. “The task ahead—to provide state-of-the-art floodplain mapping for Iowa—is daunting and challenging. … But we are confident that our partnership with the IFC will be successful.”

A Great Place to Be

University of Iowa students, too, will benefit. Their work is essential to the project, and they will take away tremendous practical applied engineering experience. Graduate student Nick Thomas came to Iowa with an undergraduate engineering degree from the University of Minnesota in the fall of 2010, just in time to get in on the start of the floodplain mapping project.

Thomas believes this experience will serve him well no matter where his career leads. “No matter what I do, this knowledge will be useful,” he says. “As a student, the flood center is a great place to be. Flooding is a problem for many people, and as part of a community of researchers all working toward a common goal through different means, it can be very exciting.”

He adds, “The flood center is creating great tools and technologies to better study and mitigate flood devastation, so yes, I do feel that it is important.”

When the maps are complete, Young says, they will guide floodplain regulation and management. Iowans will be able to access them on the Internet to better understand and identify their flood risks.

This project is exactly the kind of public service the Iowa Flood Center was established to provide, Young says. “This is an excellent opportunity for us to produce research that will benefit of the people of Iowa.”

Read more about the statewide floodplain mapping project.