To Green or Not to Green: Modeling Incentive-Based Programs for Green Infrastructure Investment On Privtae Properties
Communities are in need of cost-effective and innovative strategies for stormwater management infrastructure investments. This need is driven by the fact that stormwater pollution is the only major source of increasing water pollution across much of the country including sensitive waterbodies such as the Chesapeake Bay and Puget Sound. In reaction to this significant and growing source of water pollution, regulations at the Federal, State and local level continue to become more stringent, the level of treatment for runoff continues to increase. This reaction by the regulatory sector is driving an increase in stormwater infrastructure investment needs. The use of green stormwater infrastructure (GSI) and retention-based standards is on the rise across the U.S., but it is still considered a novel or innovative approach in many areas. The basis of the interest in GSI from the stormwater and wet weather sector is based upon the premise that retaining water on-site is more cost-effective in addressing issues such as combined sewer overflows (CSOs), treats the pollution within runoff while replenishing groundwater resources, and provides co-benefits water quality and quantity treatment, such as improved air quality, enhanced property values, and improved social well-being.
Considering that the goal of GSI is to retain runoff on-site, which is a decentralized approach to stormwater management that impacts significant segments of the landscape, the issue of treating stormwater on all types of properties, including private property is on the rise. This issue is multiplied for regulated entities who cannot meet regulatory requirements by implementing GSI on publically-owned land alone. For this reason, some municipalities are investigating the use of incentive-based programs to address the significant amount of stormwater runoff treatment required in permits. Understanding how incentive-based programs function requires a method of analysis reflecting the disaggregated and varying nature of decision-making by individuals, which can be irrational, inconsistent and driven by both monetary and non-monetary factors. Unlike idealized and mechanized systems, the dynamics associated with large populations of individual decision-makers is inherently non-deterministic. The field of computational social science has arisen to simulate how large populations of decision-makers behave, and what patterns emerge based upon varying initial conditions by using GIS and survey-driven data and tools such as cellular automata and agent-based modeling (ABM). This approach is consistent with the investigation investment policies and strategies associated with the GSI adoption at the site level by private property owners, which is at the heart of the proposed research associated with this presentation.
The presentation will provide an overview of a methodology developed to simulate the amount and distribution of GSI investment in a given area based upon the use of incentive-based frameworks, such as a traditional fee/credit approach as well as non-traditional approaches, with an example being the Stormwater Retention Credit program established recently by the District Department of Environment (DDOE) that proposes to trade retention “credits” across the District to take advantage of cost heterogeneity and generate GSI implementation in area that can stand to benefit the most from the environmental, economic and social benefits associated with this infrastructure. Policies and strategies associated with these approaches, such as subsidies, project aggregation and escalating fee and rebate scales, will be discussed as well. It should be noted that other communities, such as Chattanooga, TN and some West Coast cities have expressed an interest in a trading program similar to DDOE's, so the ability to transfer this approach beyond the District of Columbia will also be discussed.