Stormwater systems across the country are being pushed beyond their limits. As storm events grow more intense, more frequent, and more variable, it’s clear that long‑standing stormwater design criteria—built around outdated assumptions and simplified rainfall models—can no longer provide the level of protection communities need. Traditional approaches that size infrastructure for a single, hypothetical storm event fail to account for today’s data, today’s climate, and today’s risk.

Modern datasets, including high‑resolution digital elevation models and spatial rainfall products, now reveal watershed behavior with unprecedented clarity. These insights show that legacy design standards routinely underestimate flood impacts, overlook downstream vulnerabilities, and increase long‑term system costs. If communities want to protect critical assets, reduce flooding, and invest their dollars more effectively, they must move toward updated, scenario‑based stormwater design criteria that reflect the realities of a changing environment.

This presentation highlights why new design standards are urgently needed—and how utilities can adopt them. Attendees will explore how multi‑event modeling, adaptive criteria, and integrated wet‑weather planning can create solutions that work across a broad range of storm conditions, rather than a single design storm from decades‑old tables. By modernizing design criteria, communities can reduce downstream risk, extend infrastructure life, and develop more sustainable capital improvement strategies.

Learning Objectives:

· Explain the limitations of traditional stormwater design criteria based on single-storm assumptions and outdated rainfall data.
· Identify how modern datasets and watershed modeling tools reveal flood risks and infrastructure vulnerabilities that legacy standards may overlook.
· Describe how multi-event modeling and adaptive stormwater design criteria can improve flood resilience, infrastructure performance, and long-term capital planning.