Mary Atkins, P.E., CPESC, LEED AP and Kasey Marley, P.E. contributed their expertise to this piece. Mary has worked at Wessler since 2000 and serves as Vice President with experience in stormwater drainage, environmental planning and permitting projects.
Kasey has been with Wessler since 2015 and serves as the Stormwater Group Head, with extensive experience in drainage improvements and stormwater studies and master plans.
The historic flooding experienced across Indiana and Ohio last month is a powerful reminder of the importance of effective stormwater management...and the limits of even well-designed infrastructure.
Beginning August 11, multiple rounds of severe thunderstorms brought extraordinary rainfall to parts of the Hoosier and Buckeye states. Some locations received more than a foot of rain, while the White River reached levels not seen in more than a century. The National Weather Service reported record flooding at several locations, with washed-out roads, damaged property, water rescues, and widespread infrastructure impacts.
With flooding fresh in the minds of communities, it is worth asking: How much can proper stormwater management practices actually do to prevent flooding?
The answer is: a lot...but not everything.
Effective stormwater infrastructure is designed to safely collect, convey, store, and release stormwater runoff. Storm sewers, culverts, swales, inlets, and other drainage conveyances can help move water away from homes, roads, businesses, and critical infrastructure. Many communities try to manage stormwater by requiring developers to meet detention and water quality standards in their stormwater designs to store and treat stormwater runoff before it leaves the development.
Among other factors, practical stormwater designs consider how much rainfall a stormwater system can reasonably be expected to handle. When properly sized and maintained, these systems can reduce flooding impacts, prevent drainage backups, and reduce negative impacts to downstream water quality.
But every stormwater system has a limit.
When rainfall exceeds the design capacity of a stormwater system, or when the ground is already saturated, there may simply be nowhere for additional water to go. That is particularly important to note during events like the August 2026 flooding, when repeated storms moved across already-saturated portions of Indiana and Ohio.
Stormwater management isn't just about moving water away from developed properties and other infrastructure. It is also about controlling what the water carries with it.
Post-construction stormwater pollution prevention measures, such as retention and detention ponds, vegetated areas, inlet and outlet protection, and properly designed channels help keep pollutants from our receiving streams. These practices can protect waterways, deter erosion, and reduce sediment entering storm drains helping to maintain the capacity of stormwater infrastructure.
Over time, uncontrolled erosion and the accumulation of pollutants can contribute to sediment buildup in ditches, streams, detention facilities, and other stormwater infrastructure - reducing their effectiveness when they are needed most.
Perhaps the most important lesson from the recent flooding is that stormwater infrastructure cannot eliminate flood risk entirely.
An appropriately designed stormwater system can significantly reduce flooding from typical and design-level storms, but extraordinary events can exceed the design. During the recent storms, some areas received more than 12 inches of rain in only two days. The White River reached record levels in Anderson, Noblesville and other communities.
When rainfall reaches historic levels, rivers rise beyond their banks, floodplains fill, and stormwater systems can become overwhelmed. At that point, flooding may occur even where stormwater infrastructure is functioning as designed.
The goal of stormwater engineering isn't to promise that flooding will never happen. It is to reduce risk, manage stormwater runoff, protect infrastructure, and build more resilient communities for when extreme events occur.
The recent flooding demonstrates why communities should continue investing in thoughtful stormwater design standards, stormwater quality measures, floodplain planning, and infrastructure improvements as well as continuing to conduct routine maintenance and inspections and implement erosion control efforts.
We cannot control how much rain falls, but we can control how prepared our communities are to manage it.
Proper stormwater management won't prevent every flood. But when designed, maintained, and implemented correctly, it can make a significant difference in protecting people, property, infrastructure, and our waterways when the next major storm arrives.