By Denise Di Santo
Traditionally, stormwater has been regarded as a wastewater product – conveyed off land to receiving waters through grey infrastructure via pipes, pumps and ponds. The approach is not serving us well, nor is this sustainable for ecosystems that rely on healthy, integrative systems to exist. This is because in the context of the built urban system, we are creating evermore-impervious surfaces that serve to further degrade water quality and watershed function.
Stormwater management is evolving as a more holistic undertaking, where stormwater is being treated, literally, as a vital component of water resources and our natural resource base.
Low Impact Development (LID) is an innovative stormwater management approach that follows a basic principle modeled after nature: manage rainfall and snowmelt where it meets with land, allowing it to be intercepted, infiltrated, and treated before it is introduced to receiving waters. These processes also provide flow control, and work to balance water quantity as water cycles through the system. The idea is to mimic natural processes and maintain or restore hydrologic function through the use of retained landscape features, and integrating green infrastructure, which includes raingardens, green roofs, permeable pavement, and biofiltration facilities. These are regarded as LID best management practices and are sometimes referred to as green stormwater infrastructure (GSI).
Working in tandem with grey infrastructure, green infrastructure decentralizes and supplements the treatment train, resulting in improved stormwater quality and reduced runoff throughout the drainage area. These enhancements in the stormwater management system are key to creating resilience at the site, catchment and watershed scales.
Although considered innovative, LID is not a new concept. As an example, I encourage you to explore Ian McHarg’s book, Design with Nature, first published in 1969. To conceptualize human impositions on natural environments and the need to reverse our impacts, McHarg, who had a central role in the development of environmental planning, is quoted: “Let us green the earth, restore the earth, heal the earth....”
In a sense, LID is part of the landscape architect paradigm integrating natural features and function with built form.
Vegetated strips in parking area for interception, infiltration and treatment (note cuts for inflow). Image: University of Nevada Cooperative Extension
Throughout North America, the shift back to nature-based solutions is becoming more commonplace. Although regulatory requirements associate the use of green infrastructure with water quality improvement and flow control, a long list of benefits are also realized.
These benefits are identified through life cycle benefit-cost analyses and include:
- improved air quality and reduced ambient temperatures
- landscape aesthetics and increased property values
- reduced stream erosion in receiving waters
- aquatic ecosystem health for fish and other species
- mental well-being and physical health, and
- providing critical terrestrial habitat.
In addition, natural and green infrastructure accrue value over time, whereas built grey infrastructure depreciates in value and requires costly lifecycle operations and maintenance and, ultimately, decommissioning.
Philadelphia, Chicago, Seattle, Vancouver and Toronto are among the leaders in establishing green infrastructure programs. In many cases, cost effectiveness and efficiency has been greater than anticipated. Programs and public-private partnerships exist to fund stormwater infrastructure retrofits, including integration of green infrastructure in the built environment, new and redeveloping. The positive return on investment has been well documented for more than a decade and it is time to take note. That said, implementation of stormwater best management practices continues to provide lessons for improvement.
|My favorite “Swale on Yale” project in Seattle aka “Capital Hill Water Quality Improvement Project” (pictured Fall 2014).
Image: KPG Interdisciplinary Design
In Alberta, and in some North American cities, innovation in stormwater management practices is largely being approached with caution by policymakers. The Alberta Low Impact Development Partnership (ALIDP), a non-profit organization, has been at the forefront of the needed engagement and training of multi-disciplinary stormwater practitioners.
A shift in thinking is required to ensure the adoption of green infrastructure and supportive policy; traditional engineer and land planning disciplines tend to look for predictable, quantifiable outcomes with cookie cutter approaches in the process of developing the land base. These certainties don’t come easy with designs that yield results not immediately assessed with numbers.
Green infrastructure technologies also need to be adapted to local conditions and soils. Local research has been limited but efforts are underway to identify the best suited technologies for Alberta. As one innovative stormwater practitioner in Seattle puts it: the approach is of: “right site, right team, right design.” The choice of LID best management practices must be suited to sites, using multidisciplinary teams, including water resource planners, landscape architects, urban designers, and engineers. To add to the challenge of thinking outside the box, water resources management requires a precautionary approach—stepping into the future of risk management, particularly in the context of climate adaptation, is no longer optional.
|Rain garden - by Rogersoh (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)] via Wikimedia Commons|
Stormwater management innovation cannot come soon enough for places like Alberta. Uncertainties and constraints of limited water supply, and associated risks with flood and drought, are now a universal driver for building adaptation capacity and watershed resilience. Consider life cycle return on investment and trade-offs of our actions.
Water reuse has become part of this equation, to ensure water quality is matched to use while at the same time, providing a form of source control at the site scale. We can no longer afford to contaminate and convey stormwater, a critical component of water supply, to ground and surface waters. Cities and counties would do well to designate and protect natural infrastructure such as wetlands that provide ecosystem services to benefit ecosystems, rather than adopting policies and practices that for the most part, remove these assets from the landscape.
It is time to also invest in stormwater best practices research, learn from other places, and monitor and adaptively manage green infrastructure, as has been done with any innovation ever adopted successfully.
Denise is a watershed planner with a passion for connecting water and people through collaboration and inclusive planning for nature-based solutions. With broad water resources management experience, Denise takes a systems approach to innovative stormwater management, ecosystem protection and recovery, and creating conditions for resilient communities.
Links from Denise for further reading on green infrastructure include:
Return on Investment - US EPA
Return on Investment - North Carolina State University
Return on Investment - ECO Northwest