With the support of the AIA College of Fellows and its 2015-2017 Latrobe Research Prize, we assembled a multidisciplinary team to accelerate the design of climate adaptation in water-stressed cities. Specifically, the Drylands Resilience Initiative set out to make it fast, easy, and affordable to capitalize on stormwater capture for aquifer recharge.
Our goal is to optimize city surfaces for stormwater capture and aquifer replenishment—even in (particularly in) cities where rain is infrequent. To do so, we need to know where, exactly, to prioritize investment in green infrastructure, and with what expected benefits? Two years later, we’ve made big progress, and we're looking for opportunities to test our work (and support yours).
What's the Challenge?
Stormwater capture is widely recognized, even in the face of drought, as one important piece in a holistic portfolio of water supplies for arid and semi-arid cities. With decreasing snowmelt, stormwater is a resource we can bank for a sunny day by storing it in local aquifers. But city surfaces, below grade and above, are highly diverse: subsurface geologies and contaminants combined with surface ground covers and land uses create a complex mosaic of water capture opportunities. Some locations suggest optimal infiltration; immediately adjacent might be a location that is entirely inappropriate for infiltration—but well suited to surface capture. The geometries are irregular, the data disparate, the appropriate responses diverse—and the time and resources necessary to customize design response to each set of conditions often prohibitive.
In water-thirsty cities, one-size-fits-all policy overlays—Low-Impact Development guidelines, for example—are well intentioned, but don’t correspond to the biophysical complexities of where capturing stormwater is a good idea, and where it isn’t. They gloss over the differences between the physical attributes of individual sites, rather than exploit them for maximum benefit, and inadvertently dilute the potential of the city’s surfaces to build its citizen’s water supplies. Even a Stormwater Master Plan, targeting a thousand publicly-owned sites, inadvertently limits our capacity to shape our own water future: watershed management restricted to publicly-owned lands isn’t fully watershed-based. It overlooks most of the city’s surfaces.
What's the Opportunity?
To get the most out of city surfaces, we are committed to science, policy, and design working together at high resolution, across scales. Where are the precise opportunities, on tens of thousands of private sites as well as public, for infiltration and surface capture? With what impact on the basin’s aquifers (and downstream flooding)? What are the classes or types of infrastructural response each site requires? And how might each tie-in to a distributed network of comparable small-scale interventions to maximize benefits city- or basin-wide?
We entered into the Latrobe Prize grant period with a prototype framework for the highest resolution stormwater/green infrastructure decision-making tool available. That computational engine is called Hazel. However, if Hazel is to have wide benefit, we needed to know more. If architects, planners, engineers, developers, and agencies had access to this streamlined data early in their planning and design processes, under what circumstances would they put such data to use? Beyond regulatory requirements (slow to evolve and cumbersome to implement), presumably teams would use such data if doing so saves money and time, increases revenues or competitive advantages, or meets/exceeds compliance standards in such a way that additional benefits, tangible and intangible, accrue to stakeholders. What would that look like?
What Were the Obstacles?
Incentivizing strategic water-smart design is the challenge at the heart of the Latrobe Prize grant. To address it, we posed two questions.
1. Metrics: How do we provide design teams and their clients with relevant ways to evaluate costs and benefits of multiple design scenarios?
2. User interface: How do we integrate streamlined decision-making data and metrics into a visual, intuitive, and iterative site-design processes?
To explore the first question, we worked closely with Rowan Roderick-Jones, engineer and director of Green Infrastructure Partnerships at The Nature Conservancy, to build out cost/benefit measures beyond mere gallons or acre-feet of storm water captured. For each gallon captured, we asked: what’s the energy savings compared to water imports (kWH)? What’s the carbon offset (tons C02E)? Using a small library of green infrastructure BMPs, what's the approximate cost per square foot (dollars expended, treatment costs avoided)? How much open space and habitat would be created? What’s the likely impact on the urban heat island effect?
Working closely with architect and Chief Deputy City Engineer Deborah Weintraub, we used City of Los Angeles Bureau of Engineering cost data to test some scenarios and build in further metrics, including projected construction, operations and maintenance costs; associated job creation; and estimated payback period.
Our colleagues at Perkins+Will developed an interface between our huge computational engine (Hazel) and the softwares designers use (Grasshopper, Rhino, Autocad). Leigh Christy and Justin Brechtel of the P+W Los Angeles office and John Haymaker, head of P+W research, developed a workflow that sent Hazel data and economic and environmental metrics to Grasshopper and Rhino for the design process, with GIS, Excel, and CAD files supplementing design outputs. Perkins+Will conducted in-house testing in both the San Francisco office (applying the tool to a regional-scale network of hundreds of infiltrating parking lots) and the Los Angeles office (applying the tool to building-, campus-, and neighborhood-scale sites).
What Did We Find Out?
As part of extensive outreach and testing, our team held presentations, discussions, q+a, and feedback sessions with over 1400 professionals and academics from an array of design disciplines, in venues large and small across North America. In Spring 2017, we invited an intrepid focus group of architects, landscape architects, planners, engineers, and resource managers to LA Cleantech Incubator to give the tools a test-drive.
We invited testing teams to generate green infrastructure proposals for a 12-acre health-care campus in Los Angeles, first working without the tools, then with them. The tools allowed users to expand and stretch the work of civil engineers, facilitating more design options earlier in the planning process with rapid cost/benefit feedback. There was strong consensus that teams could make a greater investment in an inventive design process without delays over extensive calculations, research, or consultants. The tool also allowed teams to operate strategically, with a rapid big-picture understanding of context. How could on-site moves support a city's larger hydrologic goals? leverage other forms of public investment—in housing or transit for example—for maximum hydrologic benefit? And stack mulitple opportunities—open space, habitat, social equity—to make a clear case for prioritization?
Beyond testing tool efficacy, the extensive outreach allowed us to test, informally, some of our early assumptions about applications. We began this work with a focus on arid and semi-arid lands; over the Latrobe period, we have repeatedly encountered strong interest from those working in humid cities. From Philadelphia to Austin, Orlando to Houston, planners and designers see a need for stormwater capture prioritization tools for flood control. We set out with a strong focus on building water supply, and re-affirmed its alignment with water quality. We set out with a focus on urban centers; we found interest from California's agricultural sector as it works to build sustainable groundwater management plans. We set out with a commitment to diversifying water alternatives, particularly low-carbon alternatives, in the industrialized US West; we have found strong interest coming from traditional societies and vulnerable communities on other continents.
As team-member Rowan Roderick Jones of the Nature Conservancy puts it, Hazel is working at a crossroads of need and activity. Seven hundred cities in the US face legal action by the USEPA for better stewardship of stormwater, but with $100 billion in hardware repairs needed, limited federal investment, and cash-strapped cities, there’s a growing funding gap. Public-private partnerships can potentially reduce that gap, as they are in Detroit and Philadelphia, Atlanta and Washington. Stormwater credit trading is one way to grease public-private collaboration, and Hazel is well positioned to support those markets. Not unlike carbon cap-and-trade, stormwater credit trading allows the stormwater management requirements of one property (usually mandated under a city ordinance) to be offset by voluntary stormwater management activity in another location. Hazel’s capacity to identify districts, zones, and specific lots with varying degrees of hydrologic value could be essential to shaping healthy credit markets.
“A healthy market requires both strong demand for credits as well as strong supply––and the supply side can be tricky,” as Rowan says. “It takes significant organization and resources for a supply-side actor to find suitable sites, develop and certify credits, and they need to be reasonably assured that they will be able to sell credits on the back end.
“Tools like Hazel can help in the early assessment on the demand side, while also identifying suitable sites for credit supply. Using Hazel, credit supply-side actors, like the Nature Conservancy (or other advocates) could quickly identify where the demand is coming from and assess the scale of the demand and find suitable locations to begin planning credit supply projects. Hazel gives us a window into where and how to best implement green infrastructure to take advantage of underlying conditions and maximize private investments.”
After a brief hiatus, returning our attentions to some of our other obligations, our team is re-grouping. We are actively seeking opportunities to continue applying, testing, and bringing our tools to widest benefit.
We are grateful to the AIA College of Fellows, our industry partners, and colleagues far and wide for supporting this work.