The Future of Stormwater Infrastructure: Addressing Undersizing and Inaccurate Precipitation Estimates
As the Midwest faces the challenges of climate change, stormwater infrastructure designed for past conditions is increasingly inadequate. Historical precipitation estimates, once thought reliable, are no longer sufficient for modern stormwater management.
Understanding the Root Causes of Stormwater Management System Undersizing
The undersizing of stormwater systems has become a critical issue, leading to higher risks of flooding, infrastructure failures, and environmental damage. To understand this problem, it is essential to examine why stormwater systems were undersized in the first place and why precipitation estimates have historically been too low.
1. Historical Precipitation Assumptions
For many years, stormwater systems were designed based on historical precipitation data, which assume a level of relative stability. Engineers typically used design standards such as the 100-year storm (a storm with a 1% chance of occurring each year) to size drainage systems. While this model served well in stable climatic conditions, it has become inaccurate due to the increasing frequency and severity of rainfall events.
2. Limited Historical Data for Extreme Weather
The primary data used for stormwatersystem design has historically come from long-term precipitation records. However, extreme events like heavy rainfall and thunderstorms were considered rare, and their frequency and intensity were not fully understood. As a result, stormwater infrastructure was built to handle average rainfall conditions rather than extreme events, underestimating the volume of runoff that would need to be managed during intense storms.
In the past, large, high-impact storms, such as those with 100-year return periods, were treated as rare occurrences. This model is now outdated, leaving stormwater systems and the surrounding infrastructure at risk.
3. Lack of Localized Climate Data
Generalized climate models have often been used for stormwater system design, leaving out localized weather patterns that may be specific to a region. These models tend to overlook the regional variations in precipitation trends and the unique microclimates found in different parts of the Midwest.
As a result, cities and towns built their systems using one-size-fits-all solutions that failed to account for localized shifts in precipitation. This further contributes to undersized infrastructure, as the data used did not reflect the full range of future weather conditions.
Adapting to Future Needs
In order to properly size future stormwater systems, communities must adapt their infrastructure designs to better reflect modern precipitation trends. This requires integrating climate projections, flexible design strategies, and innovative technologies into stormwater planning.
Climate-Informed Design
The EPA SWMM-CAT (Storm Water Management Model – Climate Adjustment Tool) is an extension of the EPA’s SWMM software designed to help stormwater users assess the potential impacts of climate change on stormwater infrastructure. It allows users to adjust rainfall and temperature inputs in their SWMM models based on various climate projection scenarios, helping communities evaluate future flood risks and infrastructure resilience.
By examining future climate scenarios, municipalities can ensure that their infrastructure is built with resilience in mind, accounting for intensified rainfall and potential flooding risks.
Flexible Infrastructure
Stormwater systems should be designed with future expansion in mind. For example, stormwater storage basins and detention ponds can be sized to accommodate additional capacity as needed. Green infrastructure, like permeable pavements and rain gardens, also helps reduce runoff and ease pressure on traditional systems by managing stormwater on-site.
Localized Climate Data
Municipalities should prioritize localized precipitation data to ensure that designs are reflective of regional climate trends. This more granular approach allows for a better understanding of future weather conditions, improving the accuracy of infrastructure sizing.
Incremental Stormwater Infrastructure Upgrades
For communities with limited budgets, upgrading stormwater infrastructure gradually can ensure that high-risk areas are addressed first, and other areas can be improved over time. This phased approach helps mitigate costs while ensuring more effective long-term stormwater management.
Planning Stormwater Systems for a Changing Climate
The issue of undersizing stormwater infrastructure is rooted in outdated precipitation estimates and the failure to fully account for the effects of climate change on rainfall patterns. As extreme weather becomes more frequent and intense, existing stormwater systems designed for past conditions fail at an increased rate.
To prevent future failures and reduce the risks of flooding, municipalities should consider adopting climate-informed design practices, investing in flexible infrastructure, and examining localized precipitation data to better plan for the challenges of tomorrow’s storms.
Ready to Take a Proactive Approach to Your Community’s Stormwater Challenges?
Our team of stormwater engineers can help you assess existing systems, interpret localized data, and develop solutions that adapt to changing climate conditions. Contact us today – let’s work together to build resilient, future-ready infrastructure that protects both people and property.