A track record built at Iowa

The city of Dubuque, Iowa, came to IIHR seeking help for a major challenge arising from a concentrated urban watershed.

The Bee Branch Creek watershed encompasses water captured in the bluffs overlooking the Mississippi River through historic city neighborhoods before pooling into a basin adjacent to the Mississippi. As Dubuque grew, increasing amounts of water overwhelmed the city’s aging and undersized storm sewer system.

Between 1999 and 2011, Dubuque endured flooding that resulted in six presidential disaster declarations. Although the city has a two-pump station to transfer water from the pooled basin to the Mississippi, the facility could be overwhelmed if a pump were to fail during storms that are increasing in frequency and intensity.

Dubuque contracted with IIHR to evaluate how adding two pumps could improve the system’s performance, particularly by creating redundancy. At IIHR’s facility, located in the UI’s Oakdale Research campus, engineers built a scaled model of the proposed four-pump system. During a recent visit, IIHR engineers Bob Everhart and Tony Loeser demonstrated how water flows into four bays and swirls upward through pumping tubes.

The objective is to ensure that the system can handle up to 560 million gallons of water — the equivalent of about 1,000 Olympic-sized swimming pools — while minimizing bubbles and vortices that can strain pumps and shorten their lifespan.

“We want to get the water to flow as evenly as possible,” Loeser said above the watery din, “so these pumps work for a long time and serve the city as best as possible.”

The pump design and testing are important pieces of the Bee Branch Watershed Flood Mitigation Project, a $250 million, 20-year investment by Dubuque to better manage stormwater.

“It will give us the ability to pump more water as those rain events get bigger and bigger,” says Jim Bousley, project manager for the city of Dubuque. “That security from a flood standpoint for the downtown area definitely is the biggest bang for the buck.”

IIHR conducted a similar study for Cedar Rapids in 2022, testing designs for two stormwater pumping stations that were to be constructed as part of the Cedar Rapids Flood Control Project. Engineers used physical models to evaluate flow behavior and ensure that the designs met pump station standards.

Three years earlier, IIHR had contracted with Keokuk to design plans for a system that would divert stormwater away from the city’s sewer network. During heavy rains, the existing system could produce sewage-infused overflows into the Mississippi River.

The project included a series of drop shafts leading to a tunnel system that channels stormwater directly to the river, bypassing Keokuk’s sewer system.

“The design was tested and improved to provide a balance of hydraulic efficiency, maintenance accessibility, and cost-effectiveness for the community,” Loeser says.

From the Midwest to the world

IIHR has been in the stormwater business since shortly after its founding in 1920, studying how water flows on roads, through culverts and tiles, and in curved pipes, while designing improved systems. One of its earliest projects involved more than 3,300 water-flow tests running the Iowa River through channels created in the basement of the C. Maxwell Stanley Hydraulics Laboratory, where IIHR’s main offices still are located.

IIHR expanded its stormwater research in the 1980s as cities wrestled with systems that could no longer handle the volumes driven by population growth. In Milwaukee, former IIHR director Jack Kennedy and engineer Subhash Jain developed a landmark tangential vortex inlet drop shaft system to reduce flooding and unwanted discharges from the city’s combined sewer and stormwater system.

“These cities basically had infrastructure issues,” Lyons says. “Their pipes and channels were not big enough to handle those overflows and mitigate urban flooding.”

That expertise continues today. For London, IIHR designed a drop shaft and tunnel network to address combined stormwater and sewage overflows into the Thames River. In St. Louis, engineers designed and built a scaled replica of drop shafts at the city’s Forest Park Intake Facility to optimize performance during peak flows, when up to 4.4 billion gallons of water could rush into the system.

In Abu Dhabi, IIHR engineers from 2009 to 2010 tested a variety of channel and tunnel configurations for a new sewer tunnel system that was being designed to serve the capital of the United Arab Emirates. The research yielded key findings related to minimizing odor and moving air more efficiently through the sewer system.

In a seven-year project that ended in 2013, IIHR built and tested physical models to support the DC Water’s Clean Rivers Project, a nearly $3 billion undertaking by Washington, D.C., to capture and clean wastewater during rainfalls before it reaches rivers through and around our nation’s capital. As part of the research, engineers studied flow rates and trapped air in a vortex-type drop structure that at the time was one of the largest in the world.

A new partnership with New York City focuses on the Newtown Creek wastewater system. The creek, which flows between the densely populated boroughs of Brooklyn and Queens, floods even during light rains, causing wastewater to be released. IIHR engineers will test designs to minimize combined sewer overflows into the creek. They presented their research during a tour associated with the “Discover Your University” series May 19.

“The Newtown Creek project showcases IIHR’s unique experimental capabilities in supporting some of the world’s largest and most complex stormwater infrastructure projects,” Lyons says.

Why Clark County enlisted IIHR

In February, a delegation from the District visited IIHR’s Oakdale facility to get a progress report on its contracted stormwater project. IIHR engineers and Clark County officials stood on a roadway model that had been built originally to evaluate stormwater inlets for the Ohio Department of Transportation, which wanted to minimize the buildup of trash and debris at these drains. IIHR drafters took designs and photos sent by Clark County to configure a 50-foot long by 12-foot-wide lane of county highway, which IIHR carpenters, machinists, and welders built to exact specifications.

On that custom-built highway lane, IIHR engineers had placed different designs of stormwater grates and examined several scenarios: the size of openings in grates; the angle and slope of grates; and the number and dispersal of grates. They then subjected those grate configurations and locations to changing water flow rates, depths, and velocity — all to maximize the volume flowing into the inlets and emptying into shafts and tunnels, and away from flooding that can harm people and property.

Loeser says the testing revealed that the physics of water movement on the road and through stormwater inlets is quite complex.

“It’s not a uniform, one-dimensional flow,” he says.

Rowley says IIHR’s analysis could lead to optimized inlet, curb, and grate configurations to collect as much water in future roadway design and construction across Clark County.

“When it rains, we can't just stand in the middle of the road and watch how these inlets perform,” Rowley says. “Partnering with the University of Iowa gives us access to the expertise, facilities, and physical modeling capabilities we need.”

It’s the type of research that should yield municipal clients for years to come, as cities wrestle with infrastructure challenges brought by population growth, intensified rains linked to climate change, and the need to fold stormwater runoff into watershed planning.

“Stormwater infrastructure exists all across the U.S.,” Lyons says. “What we're learning here could apply almost anywhere that uses inlets along their curb and gutters in their communities.”