Erik Porse, PhD

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Hybridization in Stormwater Infrastructure and Governance

Water infrastructure is typically about pipes and bills.  Most cities have dedicated departments that manage water distribution, sewage, and stormwater systems.  Today, however, new designs for more sustainable urban development are re-considering how we deliver these services for residents.  Rather than provide and manage water through centralized services, what are the opportunities and challenges associated with new models of infrastructure that may not be centrally-managed: local water reuse, Low-Impact Development (LID) and stormwater infiltration, rainwater harvesting, and more.  Are these methods viable as a long-term strategy?  Moreover, how is a system comprised of these design components aligned with our current organization and management structures in municipalities?  The answer is not well, but many cities are working on this problem.  This post is part of a series related to a recent article I authored in the open-source journal Water that considers stormwater governance in future cities.

Stormwater management systems include structural measures that convey runoff and facilitate centralized treatment, as well as landscape approaches that promote infiltration on public or private property. Hybridized urban stormwater systems combine structural approaches (conveyance) with distributed landscape treatments (infiltration) to reduce runoff and improve water quality. While past management emphasized construction of conveyance infrastructure, urban landscapes have always provided some level of infiltration. Moving forward, agencies are recognizing the value of infiltration. This categorization is useful in describing approaches for physical management of urban runoff, but it does not describe potential differences in stormwater governance structures. Distributed infrastructure does not necessarily imply distributed management. In cities with established stormwater infrastructure, residents have traditionally not actively participated in management of either conveyance or infiltration infrastructure. This, however, may be changing in many cities.

A more nuanced conceptual model of future urban stormwater management encompasses both hybridized infrastructure and hybridized governance. Hybridized infrastructure combines conveyance and infiltration. Hybridized governance disperses management and monetary responsibilities between central experts and private landowners. An effective stormwater management system could theoretically combine hybridized infrastructure with central management, where agencies would be responsible for funding landscape treatments, administering landowner incentives, monitoring runoff and performing maintenance. A central authority could also dictate zoning requirements, acquire land, and conduct maintenance for conveyance and infiltration zones as part of flood management. Alternatively, a hybridized governance structure for distributed infrastructure may have a central authority managing structural measures, but provide incentives, education, or regulations to landowners who undertake autonomous actions. Figure 1 illustrates this model, with one axis representing a gradient of centralization in infrastructure and the other axis representing a gradient of centralization in management. Some examples for design and management are highlighted.

While cities are testing approaches that combine some hybridization in infrastructure (conveyance and infiltration), hybridization in governance (dispersal of construction and monitoring duties) remains less explored. In hybrid governance structures, difficult questions arise regarding the ability of system managers to assure proper operation when individual responsibility is prominent. Alternatively, many cities with poor existing infrastructure have by default distributed management and funding structures. Both governance and infrastructure change with time, for a century ago, many wealthy cities today lacked both structural measures and institutional oversight.


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