Modeling Hydrologic Effects of Urbanization Using a Coupled Natural-Human Systems Model

There is widespread recognition that traditional stormwater control measures (SCMs) often do not prevent degradation of urban watersheds. The cumulative effect of urbanization alters hydrologic fluxes such as evapotranspiration and infiltration, and ultimately the timing and distribution of stream flows. In the Portland, Oregon area, stormwater managers are increasingly addressing stormwater management needs by combining watershed-scale planning that preserves riparian corridors and public open space with neighborhood-scale design and construction standards that emphasize infiltration-based SCMs. To test the potential effectiveness of these combined strategies, we used a coupled natural-human systems model to simulate the effects of urbanization on the water balance and distribution of stream flows in a 4000 hectare watershed on the outskirts of Portland, Oregon. The future scenarios we evaluated were developed during a two year stakeholder-researcher collaborative process that identified plausible future development patterns and stormwater management approaches.