Understanding urban development and water quality through scenarios

The Clean Air Act establishes a framework for regions to target environmental outcomes related to air quality in long-range transportation planning in the United States. Similarly, the Clean Water Act establishes a framework for regions to improve their environmental performance regarding water quality standards when regulating land development. However, these policy and planning frameworks do not reflect the well-established relationship between transportation and land use. Is this a problem? I applied the land use/transportation model TRANUS in parallel with the EPA's Storm Water Management Model (SWMM) to simulate the water quality outcomes of two alternative long-range transportation plans for Mecklenburg County in North Carolina. I found that alternative regional urban forms can significantly influence only the spatial pattern of stormwater runoff.;This finding departs substantially from previous research suggesting that development strategies that promote densification can reduce per capita stormwater runoff. These results suggest that regional growth management strategies developed to meet air quality goals are not optimal for meeting watershed protection goals. Parallel and competing planning processes for land use and transportation produce suboptimal outcomes. In the context of a region, municipalities and planners have multiple goals at different scales which are sometimes in conflict. Achieving full transparency about tradeoffs between alternatives is particularly fraught because the costs and benefits inherent in these competing goals are not experienced at the same spatial scale, or by the same localities or classes of people. With regard to environmental performance, the federal government plays a unique role in mandating planning and promoting best management practices. The results of this study suggest that there is a real opportunity for the EPA and USDOT to integrate transportation and land use planning through regulatory requirements and incentives.