Cost/Benefit Analysis

Design Features

The Cost/Benefit Analysis component of the T.R.E.E.S. Project produced a tool that's helping Los Angeles-area planners evaluate the socioeconomic and natural resource impacts of urban forestry best management practices (BMPs). Such evaluations will be useful to decision makers and the interested public in promoting T.R.E.E.S. BMPs as alternatives to conventional design strategies. The Cost/Benefit Analysis was designed to:

• produce reliable data on a range of practical, cost-effective BMPs with the potential to improve the environment while generating non-monetary social benefits;
• describe the effects of BMPs on a wide range of environmental and socioeconomic conditions including water availability and quality, flood control, air quality, energy demand, greenwaste supply, capital and operational costs, employment and quality of life;
• make maximum use of the best existing information
• provide a blueprint for a GIS- (geographic information system) based computer model that would allow users to select study areas ranging from a single census tract to all of Los Angeles County

Development Process

The following process was used to develop the Cost/Benefit Analysis:

A list of potentially applicable best management practices (BMPs) was developed. This list was then screened to select those BMPs with high potential for widespread implementation in Los Angeles, low cost/benefit ratios, and sufficient databases to allow reliable description of their effects. The BMPs meeting these criteria included:

• strategic tree planting
• other tree planting
• tree maintenance
• mulching
• cistern installation
• drywell installation
• graywater system installation
• pavement removal

A map, or schematic diagram, was developed showing connections between the BMPs and the key environmental and economic components. The environmental components included air quality, energy demand, water supply and demand, water quality, flood control, and greenwaste production; the economic components included capital, operational and administrative costs, and employment impacts.

Analytical modules were developed for each of the environmental components. Linkages identified in the map were translated into hypothetical formulas.

The hypothetical formulas were specified as a series of quantitative response functions comprising each module. Response function specification involved intensive data collection from published and unpublished reports and interviews with leading experts on the topics addressed by each module. In some cases, statistical estimation (i.e., regression analysis) was applied to generate response function coefficients. Socioeconomic relationships were specified using similar methods.

For each module, a briefing report was prepared summarizing the relevant response functions proposed for incorporation into the C/B analysis. For each response function, the report indicated:

• the units in which variables were to be measured;
• the data needed to run the model;
• the information sources used;
• limitations on and caveats regarding the use of the response function in the analysis;
• the ranges within which response functions are valid;
• and relevant information gaps.

Each briefing report was subjected to at least two rounds of peer review by project-team scientists, followed by two rounds of review by leading scientists from academia and government agencies. The final briefing reports were the basis for the five technical reports included in the analysis.

Focus groups were conducted for each module. Participants included key project-team members and selected government agency administrators representing the prospective user community. The focus groups provided a final round of technical review to assure quality and maximize analysis usability.

An interactive GIS-based computer model was developed from the equations and data of the Cost-Benefit Analysis.