By 2030 the U.S. will lose around $520 billion annually from its gross domestic product due to flooding. New risks resulting from climate change arise not only from swelling rivers and lakes, but also from stormwater runoff. According to the World Bank, coastal cities risk flooding more from their poor management of surface water than they do from rising sea levels. Surface water liability governs when a landowner is responsible for diverting the flow of water to a neighboring parcel of land. Steep increases in urban flooding will make surface water an enormous source of litigation in the coming decades. But surface water jurisprudence is ill equipped for this influx. The law of surface waters remains cumbersome, antiquated, and confusing. Furthermore, the doctrine itself has exacerbated the problem by privileging land development over maintaining natural landscapes, thereby eliminating what would have been carbon sequestration devices, as well as natural buffers against storm surges, sea level rise, and flooding. This Article critiques surface water liability rules through original research into the agricultural science that supported these legal doctrines. By establishing how the current legal doctrines emerged from science now known to be highly flawed, this Article demonstrates the need to break with past doctrines and engage in a genuine rethinking of how to manage surface water liability in the twentyfirst century. Finally, this Article proposes a new liability rule that would manage landowner expectations while avoiding the pro-development bias currently entrenched in the jurisprudence.