Decision Making on the Gray-Green Stormwater Infrastructure Continuum

Abstract

Prioritizing stormwater infrastructure projects is challenging. In addition to regulating runoff and complying with water quality standards, agencies also consider factors such as life cycle costs, environmental impacts, and cobenefits to the environment and community. This work reviews literature on these decision-making criteria for stormwater projects, relates them to specific types of stormwater control measures (SCMs), and presents findings from an expert panel consultation regarding the relative importance of criteria for stormwater-related decision-making. Additionally, the work formalizes the concept of a gray-green stormwater infrastructure continuum. The more common approach of classifying infrastructure as gray or green poses analytical challenges, given that individual SCMs often have material, size, process, and other characteristics that are not strictly gray or green. Framing stormwater control infrastructure as being along a continuum allows both greater analytical flexibility and a more explicit consideration of the variety of inputs that decision makers consider. Within the context of the gray-green stormwater infrastructure continuum, the review of decision-making criteria and a panel consultation provide a valuable resource for developers of decision support tools that integrate these complex criteria in a way that is beneficial to potential end users.