Contextualizing and communicating the ancillary benefits of green stormwater infrastructure

Abstract

As we move into an era of increased urbanization, stormwater practitioners are charged with creating multi-functional solutions through the installation of stormwater control measures (SCMs). Green stormwater infrastructure (GSI) mirrors natural hydrologic processes and can be used as an alternative or complement to traditional grey infrastructure. To encourage greener interventions, practitioners promote co-benefits (ancillary social, ecological and environmental outcomes). Co-benefits are difficult to quantify because they span a diverse set of categories that cannot be easily measured with a single metric. This dissertation advances the science of co-benefits by querying (1) the impact greening programs have on vegetation in cities, (2) the public’s preference for GSI and co-benefits, and (3) the feasibility of incorporating co-benefits into the planning process. First, a ten-city greenness study found that robust GSI programs did not always correspond with increased city-wide greenness. In Philadelphia, the installation of non-vegetated SCMs contributed to decreased urban greenness. Second, a survey administered in three cities found that respondents preferred new GSI installations and had less confidence in GSI to handle storms. The co-benefits surveyed were favorable to most respondents, but a clear divide was identified between environmental and socio-economic related benefits. Finally, a critical review of the literature informed a SCM/benefit attribution matrix that was then applied to a case study in the Berkeley neighborhood of Denver, CO. We found that hydrologic benefits related to SCMs can be quantified using stormwater modeling. To assess vegetated benefits related to SCMs, we created the framework of the 4 C’s (community, context, connectivity and canopy) to leverage surrounding urban green infrastructure (like parks) because the modeled solution would add only 1% to the neighborhood’s vegetated area. To incorporate the results of this dissertation into stormwater planning, we advocate that municipalities adopt multi-department integrated vegetation goals to optimize the benefits of all types of urban green infrastructure.