ECOHYDROLOGICAL PROCESSES AT THE WATERSHED SCALE: GREY TO GREEN EVOLUTION OF URBAN SYSTEMS

Urbanization is transforming increasing areas of the landscape as existing cities continue to expand, and core urban areas redevelop. The emergence of megacities at the global scale is producing metropolitan areas of tens to more than one hundred million people over regional scales, becoming dominant land uses of major watersheds. The reliance of cities in the 20^th century on grey infrastructure to manage urban water was initially to accelerate drainage rates and improve human health. This approach is increasingly considered insufficient to sustainably manage stormwater, and is being complemented by the design and implementation of green infrastructure to improve retention of stormwater and contaminants. This presentation centers on the design, implementation and testing of green infrastructure over a range of human dominated landscapes to recover a set of ecosystem services by reproducing the effects of coupled surface/subsurface hydrological and ecosystem processes in unmanaged areas. Adaptation of methods to local hydrogeologic conditions, social and legal context are incorporated in the form of design tools, based on distributed ecohydrologic models, to scale from individual parcels through watersheds, and explicitly considering interactions between the built environment, the natural biophysical setting and human behavior.