By Paul M. Sherer

Washington State's King County is blessed with natural abundance. Within a short drive of Seattle, rivers run thick with salmon, mountains are draped in evergreen forests, hiking and biking trails wind between the towns, and spectacular views are everywhere. These natural riches have helped draw skilled workers to King County, which grew 15 percent from 1990 to 2000. This growth, in turn, is threatening the very beauty that makes the county special.

In a time of tight budgets and rising land prices, King County's Department of Natural Resources and Parks (DNRP) must balance multiple competing mandates. Separate DNRP programs are charged with protecting endangered species, developing new parks and trails, keeping agricultural land in production, managing forestry, and preventing floods.

"We had started looking at the various business lines in the organization and noticing that we could be more effective if we had a strategy that looked across different programs," says Mark Isaacson, assistant director of DNRP's Water and Land Resources Division. "You can't buy it all, you can't own it all, so how can you be more effective with the limited dollars you have?"

Land acquisition is an important tool for DNRP in meeting these goals. But the county's budget is limited, making it crucial to identify the most important parcels for acquisition. Working with The Trust for Public Land (TPL), San Francisco, California, a national conservation nonprofit organization and a King County partner for 15 years, the county recently completed an ambitious GIS project to prioritize its land acquisition targets and help it get the biggest bang for its conservation bucks, in part through identifying acquisition targets that meet several mandates at once.

Better Understanding Land Acquisition Choices

TPL calls its GIS process Greenprinting—a method by which a community, county, region, or state can identify priority lands for conservation, new parks, and environmental management. TPL proposed a Greenprint for King County, and the county embraced the idea.

Indeed, the county was already developing a land acquisition plan and had been looking for better ways to coordinate its work to meet multiple goals. Already experienced with GIS, the county had also created an online GIS Center (www.metrokc.gov/gis).

TPL chose ArcGIS 9 Desktop (ArcView) for the project in part because of their processing power to crunch data from approximately 50 data sets describing each of the county's more than 500,000 individual land parcels. In addition, both TPL and the county saw it as an advantage that county workers were already familiar with Esri software—a potential benefit for other communities that might want to build similar models.

"We wanted to create a tool that we could hand over to the client with the least amount of training and expense," says Breece Robertson, TPL's director of GIS Design and Applications.

The GIS application allowed county officials to visualize and better understand land acquisition choices. The application was developed in partnership with Esri Business Partners Earth Analytic Inc. (Santa Fe, New Mexico) and Foresite Consulting Inc. (Loveland, Colorado). Jones & Jones (Seattle, Washington), a landscape architecture firm, also worked as a partner. The team also worked closely with county officials. The county awarded a contract for the work in October 2003.

The King County Greenprint model employs a broad range of data sets, including

• Natural resource data, such as the habitats of endangered species
• Water quality and hydrologic data
• Landscape integrity data, such as wildlife migration networks and forest fragmentation
• Demographic and socioeconomic data, helping identify population centers with little access to parks
• Regulatory data sets, such as zoning layers, which identify lands with high conservation values that may also be attractive to developers
• A list of acquisition targets already identified by DNRP
• Proposed trail linkages needed to connect local and regional trails and greenways

To create the model, all data was organized into five analysis disciplines for assessing—a parcel's resource value, gaps in existing parkland, the risk that the land might be developed, existing DNRP target acquisition parcels, and the value of the land in forming trail linkages.

TPL then set up ArcGIS to examine the data for as many as 20 submodels within each of the five disciplines. Then the submodels were linked, and a weight was assigned to each to form the final conservation priorities model layer. By overlaying that layer with a parcel data layer and applying zonal statistics, DNRP can score each parcel based on its conservation value and prioritize acquisition on the basis of these scores.

Challenges, Solutions, and Strengths

Working on a large landscape raised some challenges. Initially, TPL used vector data (point, line, and polygon data) as input data for the model. But this led to slower processing speeds and longer model run times than expected. As a result, all data was converted into a raster format (coordinates) with a 100-foot cell size, and this cut processing time for submodels from two or three hours to 10 or 15 minutes.

One of the strengths of the model is its expandability as new data becomes available. For example, Jones & Jones built a landscape integrity and scenic values model that quantifies some of the intangible factors important to the experience of a landscape, such as its views. Says Chris Overdorf, an associate at Jones & Jones, "This layer helps answer such questions as where in King County can you go and see Mt. Rainier and the Cascades, forests, and major riparian corridors without seeing transmission lines and the city of Seattle without seeing human impacts?"

As the model was being built, great pains were taken to include the knowledge and information that resided only in the experience and memories of longtime agency professionals. For this reason, the model was created with the close consultation of King County's staff. For example, one King County regional trail planner had developed his own map of where future regional trail connections could be located based on more than 30 years of institutional knowledge.

Says Jennifer Knauer, DNRP's project manager for the GIS system, "It's this kind of information that really requires on-the-ground input. Open space planning and conservation are an art as much as a science."

Roger Hoesterey, director of TPL's Northwest Region, agrees. "GIS data always has to be compared to what you actually see on the land. And in pursuing acquisitions you also have to include your knowledge of what land is available, what you can afford to purchase, and what can be approved politically."

"King County's growth challenges were straining our resources to make good land conservation decisions," says Isaacson. "But TPL's adaptation of ArcGIS helped us with a new framework for analyzing and prioritizing our land conservation needs. Without a doubt, GIS is a powerful tool."

DNRP adopted the Greenprint model in July 2004.

For more information, contact Breece Robertson, The Trust for Public Land (e-mail: breece.robertson@tpl.org), or Roger Hoesterey, The Trust for Public Land (e-mail: roger.hoesterey@tpl.org). Paul M. Sherer is a freelance writer who writes frequently about parks and open space.