Stakeholder-informed scenarios to investigate the impact of land
use/land change on nutrients, sediment and runoff in the Shenandoah
National Park, Virginia
Abstract
Land use/land cover (LULC) change could adversely affect watershed
health by elevating nutrients and sediment levels and intensifying the
risk of flooding. In this study, a spatially-explicit LULC change
modeling framework was coupled with the Chesapeake Bay Watershed Model
(CBWM) to investigate the impact of LULC change on nutrients (total
nitrogen and total phosphorous), sediment and runoff volume in the
watersheds surrounding Virginia’s Shenandoah National Park, U.S. Four
stakeholder-informed scenarios alongside a Recent Trends LULC change
scenario were studied. The stakeholder-informed LULC change scenarios,
which differed in consideration of future planning and population
growth, were developed through several meetings with stakeholders. To
develop the Recent Trends, the historical LULC trend from 2001 to 2011
was analyzed. Using 2011 as a baseline scenario, the spatio-temporal
patterns of LULC change were estimated as influenced by physiographic
and socio-economic drivers 50 years in the future (2061). The projected
LULCs were fed into the CBWM to predict the change in average annual
loading of nutrients, sediment and runoff volume. While the changes in
loads at the full study area were not substantial (< 0.9%),
changes became more pronounced at finer spatial scales. Expectedly, the
LULC change scenario with ad-hoc planning and high population growth
resulted in the largest increase in runoff volume. However, the scenario
with ad-hoc planning and low population growth showed the largest
increase in the simulated pollutants. This was because while this
scenario projected less development, it projected more increases in
agricultural LULCs that export more nutrients and sediment than other
changing LULCs. This implied that sole land use planning based on urban
development is not sufficient for watershed protection and agricultural
LULCs need to be incorporated in concert in our future planning. This
further suggested that land use planning plays a more critical role than
population growth rate in water quality management. The results have
implications for the Chesapeake Bay total maximum daily load and could
help well-informed future land use planning and watershed protection by
incorporating the impact of future LULC change on water quality and
quantity.