More than half of America's waterbodies are unsafe for swimming, fishing, and as sources of drinking due to city building and farming. Beyond water quality problems, dysfunctional streams cause flooding and erosion of property leading to neighborhood blight. Not only can this be reversed, but repair of degraded urban streams can be a powerful agent for reinventing the physical environments of post-industrial cities. This requires transdisciplinary collaboration between the fields of ecological engineering and urban design. The American city was uniquely premised on fusions of landscape and urbanism―a tradition with plenty of room for innovation.