Woods Hole Research Center

Declining water quality in the Chesapeake Bay estuary is in part the result of disruptions in the hydrological system caused by urban and suburban development throughout its 167,000 km2 watershed. A modeling system that could provide regional assessments of future development and explore the potential impacts of different regional management scenarios would be useful for a wide range of applications relevant to the future health of the Bay and its tributaries.

Woods Hole Research Center scientists have been working with an existing cell-based urban land use change model, SLEUTH (slope, land use, exclusion, urban extent, transportation, hillshade). SLEUTH is implemented in two general phases: a calibration phase, where the model is trained to replicate historic development trends and patterns, and a prediction, or forecasting, phase, where historic trends are projected into the future. Multiple forecasts can be developed to test the potential impact of different policy or land use change scenarios.

WHRC scientists have implemented SLEUTH in the Washington, DC-Baltimore, MD metropolitan region, a large and rapidly growing urban and suburban center in the Chesapeake Bay watershed where urban sprawl has been identified as a serious environmental, transportation, and quality of life issue. We have also developed forecasts of future development patterns for the state of Maryland to investigate the threat that development poses to forest resources.

About SLEUTH

SLEUTH is a pattern-based model developed by the USGS and researchers at the University of California, Santa Barbara. The model captures urban patterns through the application of four types of urban land-use change: spontaneous growth, new spreading center growth, edge growth, and road-influenced growth. These four growth types are applied sequentially during each growth cycle, or year, and are controlled through the interactions of five growth coefficients: dispersion, breed, spread, road gravity and slope.

The first four coefficients listed above describe the growth pressure in the urban system. Resistance to growth is incorporated through the slope coefficient, which captures the effect of steep slopes on restricting development, and through a user-defined excluded layer, which defines areas that are wholly (e.g. water or parks) or partially (e.g. restrictive zoning) excluded from development.

Summary of Growth Types Simulated by the SLEUTH Model

This work was funded in part by the NASA Land Cover Land Use Change Program, the Chesapeake Bay Foundation, and the National Center for Smart Growth. Collaborators at the USGS provided technical assistance.