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Ideas, initiatives, and activities from the League’s Policy Research Labs THE LAB REPORT Four Ways Communities Can Prepare for More Extreme Flooding and Weather Events GUEST AUTHOR

By Matt A. Comben

W e love our water here in Michigan. Whether it’s sitting on a beach, relaxing with a fishing pole, floating on a pontoon boat, or kids running through a sprinkler, water is a part of who we are in the Great Lakes State. Yet, over the past few years, Michiganders are experiencing more and more flooding and extreme water-related weather events. They’re costing us homes, roads, a sense of security, and even lives. Along with those climate shifts, the U.S. population nearly doubled over the past 50 years. With that growth comes demand for developed spaces. Put simply, paved land has a significant impact on water movement. Pavement— including buildings, parking lots, and roads—doesn’t allow water to penetrate the earth. What do you get when you combine excess precipitation with impervious surfaces? Floods. Here are four ways communities can prepare for more extreme flooding and weather events by proactively planning for and managing precipitation: 1. Rethink storm sewers. As parking lots are paved for new apartment complexes, big-box stores, and business districts, storm sewers must be built to accommodate growing volumes of rain. Existing infrastructure is showing us it’s increasingly incapable of managing larger and more frequent weather events. Designing storm sewers to handle this accumulation is essential to safeguarding this new infrastructure. A common first step for municipalities in rethinking storm sewers is conducting modeling and assessing current systems’ risk of failure. When the City of Richfield, Minn. looked at its 116 miles of storm sewer pipes, it was able to see its most flood prone structures and evaluate the impact of flooding on development, as well as explore

flood-mitigation options. It was also able to combine failure likelihood and severity of consequences for each storm sewer to prioritize replacement or upgrades in the way most beneficial to the city and resident’s safety.

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JANUARY / FEBRUARY 2022