Stormwater design involves creating systems that effectively manage rainfall runoff to protect water quality and prevent flooding. In Iowa, engineers and planners use established standards and practices to design stormwater management solutions that address both water quality and quantity concerns, helping communities become more resilient while protecting our waterways.
The Unified Sizing Criteria is a practical approach to managing rainwater
in our communities.
It works with different sizes of rain events—from common small showers to rare major storms. The criteria addresses four key goals: cleaning pollutants from regular rainfall, protecting streams from erosion, preventing neighborhood flooding during moderate storms, and managing water during major flood events.
The Iowa Stormwater Management Manual
The Iowa Stormwater Management Manual (ISWMM) provides practical guidelines for managing rainfall in our communities. The manual helps cities and towns meet water quality requirements while offering flexibility in how they approach stormwater management. Created specifically for Iowa’s climate, ISWMM helps communities install effective systems that capture and treat water before it reaches our waterways.
In Iowa, we receive about 28-36 inches of rainfall each year. Traditional drainage systems that quickly channel water away often cause pollution and flooding problems downstream. The ISWMM encourages practices that allow water to soak into the ground where it falls, similar to how Iowa’s native prairies naturally managed rainfall.