Impacts Of Development And Climate Change At Multiple Scales In Oregon

Abstract:

We used a multiscale, stakeholder-guided approach to develop and evaluate three alternative future scenarios for urban water systems in Oregon. Model results illustrating the different outcomes of alternative policy and management choices are intended to help inform future planning and design of development in the region. Through multiple workshops, we collaborated with our stakeholder advisory group to develop watershed- and neighborhood-scale representations of three alternative future scenarios (Current Course, Stressed Resources, Integrated Water Future). We then evaluated the response of the system. The Envision model (with most processes represented at daily time steps) was used at the scale of the entire Willamette River Basin (~30,000 km²); a modified version of Envision with SWMM-5 incorporated as a plug-in was used to evaluate impacts for a HUC-12 watershed (42.4 km²), and SWMM-5 (with processes and results represented at hourly and sub-hourly time steps) was used to model impacts at the scale of an urbanizing neighborhood (~400 ha). Visual representations, model results, and indicator-based comparisons were presented to the stakeholders to illustrate the magnitude and spatial extent of coming pressures, and compare outcomes of different options for urban water management on urban water sustainability, including co-benefits of stormwater management alternatives. Both climate change and population growth will have substantial impacts on Willamette River Basin ecosystems in the coming decades. However, the relative magnitude of direct impacts from climate change and development vary across scale and across scenario. Development patterns that lead to different proportions of vegetation/forest cover and impervious surfaces dominate system response at the neighborhood scale. Direct impacts of climate change, such as increased wildfire and loss of snowpack, dominate basin-scale processes. Both drivers influence watershed scale processes, as illustrated by changes to watershed hydrologic regimes and co-benefits.