The successful design, construction, and management of man-made structures and networks with respect to our natural environment have never been at a greater premium.

Over decades and even centuries in the United States and around the world, people have sought to build cities and environments that maintain the health of both communities of people and the environments in which they live.

The San Francisco, California, Bay Area water supply system is a perfect example. Built with great foresight and ambition, it now delivers 200,000 gallons of water per day to Bay Area users via the Hetch-Hetchy system--from a source 167 miles distant.

The large portion of the water supply of the greater Bay Area passes through the impoundments of the Alameda watershed in the East Bay and the Peninsula watershed in San Mateo County, approximately 20 miles south of San Francisco. The watersheds are maintained by the San Francisco Public Utilities Commission (SFPUC). Approximately 2.4 million residents rely on the health of these watersheds.

ArcInfo was used for an ambitious watershed management project. Researchers and managers captured, analyzed, and shared spatial data and information in new and exciting ways to establish optimum management policies.

"The complexity and comprehensiveness of the watershed management planning effort could not have been handled without GIS as a tool," says Joe Naras, land and resources manager of the San Francisco Public Utilities Commission. "For natural resources management it's a natural. Developing the watershed management plans was done using GIS because preserving the environmental and ecological values of the watersheds is critical to maintaining high water quality for citizens."

The Peninsula watershed covers 23,000 acres of nearly pristine lands. Interstate 280 runs along the ridgeline, which forms the eastern boundary of the watershed. The area east of the ridge is crowded by eight suburban cities extending from San Bruno to Redwood City. The western edge of the watershed is the crest of Montara Mountain, and several intermediate ridges divide the combined watershed. The three primary threats are fire, erosion, and pollution.

In 1992, SFPUC decided to update its watershed management plan. After intensive study, SFPUC chose to work with the environmental design firm of EDAW, an Esri Business Partner, and a team headed by EDAW's San Francisco office was established. To set goals for the project, the team worked with a group of SFPUC staff called the Watershed Planning Committee. The team also met with local communities at three points in the process to establish goals and to review interim and then final results. The primary goal was agreed to by all stakeholders: maintain and improve source water quality to protect public health and safety.

The following six secondary goals were also identified:

• Maximize the contribution of the watersheds to the water supply.
• Preserve and enhance the ecological and cultural resources of the watersheds.
• Protect the watershed, adjacent urban areas, and the public from fire and other hazards.
• Continue existing compatible uses and provide opportunities for additional compatible uses on watershed lands including educational, recreational, and scientific uses.
• Provide a balance among financial resources, revenue generation activities, and overall benefits.
• Enhance public awareness of water quality, water supply, conservation, and watershed protection activities.

SFPUC developed a GIS to help guide the resource planning phase and ultimately to manage all the watershed lands. Consequently, EDAW initiated a GIS Needs Evaluation to start the planning process. The evaluation strategy began with interviews of various personnel from all divisions within SFPUC's Water Department to assess existing software and potential future needs for data and management interactions. The next step was to develop a plan for both short- and long-term implementation of the GIS. A UNIX-based ArcInfo Workstation, including the ArcTIN and ArcGrid extensions, digitizing table, and color plotter, was selected for the initial hardware and software configuration.

Using the goals as directives, EDAW's consultant team began developing a basic GIS database and designing a process for evaluating the watershed. The United States Geological Survey (USGS) 7.5-minute quad digital data was established as the basemap, and thematic layers were assembled and registered to the base from various primary and secondary sources. The basic data types included geology and soils, elevation, hydrology, vegetation, rare or endangered plants and animals, habitats (field recorded and potential), fisheries, archaeological and historic features, land status (ownership, leases, and overlay districts), roads, trails, utilities, and recreation facilities. Digitizing and data management were accomplished with ArcInfo software's digitizing and editing capability.

Some of the basic data types were subsequently manipulated by various ArcInfo operations (such as overlay, reselect, recoding, dissolves, buffering, and latticepoly) to derive new layers. Examples of derived maps are slope (derived from elevation), vegetation fuel loads (derived from vegetation communities), and drainage protection zones from buffered hydrologic features.

Along with the basic data, the derived maps formed the building blocks of models to create vulnerability maps. A model is the set of step-by-step instructions given to the computer to combine data in mathematical manipulations or graphic overlays. EDAW developed models in a vector-based data format using ARC Macro Language (AML) routines that incorporated various ArcInfo overlay processes and manipulations of attribute data in tables. Final analyses were generally ranged into high/medium/low categories for more simplified interpretation. The modeling process ultimately resulted in the generation of five vulnerability maps for ecological resources, fire hazard, slope instability, cultural resources, and water quality.

"The real power of GIS is its analytical capabilities and its data integration," says Naras. "Our management project was quite ambitious, because it would guide policy for many, many years. Once we learned what we could do with GIS, it was obvious we needed the technology."

The high-sensitivity areas of four out of the five vulnerability maps were extracted and superimposed on a single map to form the Composite High Sensitivity Zones map within ArcInfo. The cultural sensitivity map was not included because policies were already in place to protect cultural resources.

The comprehensive data map shows that about 10 percent of the watershed have no conditions that receive a high sensitivity rating, and about 35 percent have two or more conditions with high sensitivity ratings. It is not only the proportion of high sensitivity ratings that directed formulation of the management policies but also their physical relationship to one another and to features such as roads and reservoirs. Ease of access, nearness to homes and Businesses, and visibility from the freeway all played a role in developing policies.

"We were successful with the project and that success encouraged increased GIS use," says Naras. "We started as a single shop, and now we're looking at networks with servers and clients throughout our organization."

The GIS configuration based on ArcInfo originally set up by EDAW was eventually turned over to the SFPUC staff, who maintain and continually upgrade the database and service the ongoing watershed management efforts.

"Today, GIS is used to document the health and vitality of the watershed and to continue to direct watershed management policy," says Jeremy Lukins, GIS manager of the SFPUC Land and Resources Section. "One of the biggest benefits today is the efficiency it provides. GIS allows the organization to access all the available environmental data in a very short period of time."

This article is derived from a chapter in the Esri Press book GIS for Landscape Architects (ISBN: 1-879102-64-1) by Karen C. Hanna. Esri Press books are available at better bookstores, online (www.esri.com/esripress or www.esri.com/shop), or by calling 1-800-447-9778. Outside the United States, please contact your local Esri distributor; see www.esri.com/international for a current distributor list.

For more information, contact Peter Jonas, EDAW (e-mail: jonasp@edaw.com, tel.: 415-433-1484).