Chapel Hill to require 100-year storm stormwater standards

15 August 2026.

Chapel Hill's Town Council plans to vote on increasing stormwater management requirements for new and redeveloped properties, shifting the standard from accommodating 25-year storms to 100-year storms. A 25-year storm has a four percent annual probability of occurring within a 24-hour period, while a 100-year storm has a one percent annual probability, according to a UNC planning professor.

Town Council member Melissa McCullough indicated the change supports the town's climate action and sustainability goals. She noted that historical storm data, traditionally used for probability calculations, may no longer accurately predict future conditions as climate change increases storm severity and frequency. The town aims to reduce flooding by requiring new developments to manage stormwater more comprehensively.

McCullough explained that older parts of Chapel Hill were built without modern stormwater considerations, creating ongoing challenges. The town currently funds stormwater control through a utility collected via property taxes and has constructed control structures, though some planned projects were halted due to ecosystem concerns. She suggested redeveloping existing sites rather than new construction can reduce stormwater control costs.

A professional engineer raised concerns about implementation, noting that larger projects can adjust pond depths flexibly, while smaller projects rely on fixed-depth features like bio-retention systems or artificial wetlands. He expressed worry that affordable housing developments, churches, and daycares could face disproportionate cost impacts, though he supports the overall goal. He advocated for the council to carefully consider protective measures for smaller projects before proceeding.

Readers can examine their own municipality's stormwater ordinances and development standards to compare current requirements.

Read the original reporting: The Daily Tar Heel.