Projecting land use change impacts on nutrients, sediment and runoff in multiple spatial scales: Business-as-usual vs. stakeholder-informed scenarios

Abstract

While the impact of land use/land cover (LULC) change on watersheds has been extensively studied, little attention has been given to the variability of this impact with respect to the projected LULC scenarios at a range of spatial scales. Here, a spatial LULC change model was coupled with the Chesapeake Bay Watershed Model to investigate LULC change impact on nutrients (nitrogen and phosphorous) and sediment loads and runoff volume in northwestern Virginia, U.S. Using 2011 as the baseline scenario, we examined four stakeholder-informed future (50 years hence) LULC scenarios, which differed in projection of population growth and planning strategy, along with a ‘business-as-usual’ (BAU) scenario, which projected historical LULC trends into the future. Four LULCs—Developed, Forest, Grasses and Crops—were dynamically transitioned. The difference in projected nutrient and sediment loads and runoff volume between the LULC scenarios was greater at finer spatial scales, where planning decisions are most commonly made. The LULC change scenario with reactive planning and high population growth resulted in the largest increase in runoff volume, while the scenario with reactive planning and low population growth showed the largest increase in modeled nutrient and sediment loads. These results suggested that planning strategy plays a more critical role than population growth in watershed management.