A researcher in a kayak guides an autonomous surface vehicle from M. Ani Hsieh’s lab as it maps the Schuylkill River’s bed, collecting high-resolution data that helps researchers understand how floodwaters move. Credit: M. Ani Hsieh’s ScalAR Lab New Penn research shows that Hurricane Ida wasn't a once-in-a-century anomaly but a preview of how climate change, urbanization, and aging infrastructure are rewriting flood risk. On most mornings, the Schuylkill River Trail is where many Philadelphians step out for a breath of fresh air. Runners check their splits, cyclists zip below bridges, and dog walkers clutch leashes and coffee. But after the remnants of Hurricane Ida and seven tornadoes struck Philadelphia in early September of 2021, those routines were put on pause as parts of the trail disappeared beneath a sea of sludgelike brown water. The Vine Street Expressway—running between the Schuylkill and Delaware rivers—was closed as water flooded the roadway, nearly reaching the overpasses.…