THE PUGET SOUND ECOSYSTEM PORTFOLIO MODEL: A REGIONAL ANALYSIS TO SUPPORT RESTORATION PLANNING

The U.G. Geological Survey (USGS) Puget Sound Ecosystem Portfolio Model (PSEPM) is a decision-support tool that supports land use and restoration planning in Puget Sound, Washington. This tool models changes in metrics that relate scenarios of Sound-wide land use change and shoreline modifications to nearshore biophysical changes relevant to human well-being and ecosystem services. We describe results for three sub-models within PSEPM, the Beach Erosion Index, the Recreation Model, and the Shellfish Pathogen Model, that evaluate three alternative growth scenarios: 1) Status Quo, 2) Managed Growth, and 3) Unconstrained Growth. These decadal scenarios are forecasted out to 2060 by the GIS-based ENVISION model developed at Oregon State University. Our three sub-models are intended to translate potential changes in terrestrial and nearshore land use to their effects in the nearshore environment. The Beach Erosion Index provides a score for each bluff-backed and barrier beach that indicates the potential of that beach to erode relative to other beaches due to loss of sediment from shoreline armoring. The extent of armored bluffs updrift of a beach serves as a potential measure of sediment supply loss to that beach and combined with other factors such as fetch distance, its relative potential to erode. To attribute cumulative updrift bluff armoring to a beach, a Network Analysis Upstream Accumulation method was applied in ArcGIS, which calculated for each beach the length of updrift bluffs that are armored within a drift cell, a unit of coastline that represents a sediment transport sector from source to deposition. The Recreation Model relates changes in population and land use to annual visitation rates at State Parks throughout the Sound. A regression model explaining current recreation use from 2008 State Park visitation data and the alternative future scenarios data are used to forecast and determine the differences in likely future recreational use at those parks. The Shellfish Pathogen Model relates the probability of high fecal coliform concentrations in commercial shellfish growing areas to watershed land cover patterns. The model identifies watershed area, percent cover of evergreen forest, and percent cover of development as important explanatory variables. Combined with Washington Department of Fish and Wildlife shellfish harvest records, overlaps between seasonal patterns of shellfish consumption and pathogen concentrations were identified to project where and when higher risks of exposure may occur. Finally, a Beach Value sub-model compiles presence data for beach features of value in terms quantification, such as public access and eelgrass habitat. This tool enables end-users to modify how beach value is calculated based on stated preferences, and use model results to prioritize sites for restoration based on impairment predictions from the three models discussed above.

Acronyms:

USGS U.S. Geological Survey

PSEPM Puget Sound Ecosystem Portfolio Model