Green infrastructure for climate adapted urban planning and design
Green Infrastructure has be defined as ecologically functional measures designed to handle stormwater, such as green roofs, bioswales, rain gardens, treatment wetlands, and similar elements. These measures have been used with increasing frequency to address water quality while allowing separation of combined sewers without requiring dedicated pipes to convey stormwater. A new scale and type of Green Infrastructure measures have begun to enter professional practice in relation to storm surge and flood impacts, especially for climate change adaptation solutions. While current science substantiates many limitations to purely “green” measures, successful applications have been documented where “green” components have performed well, especially hybrid measures featuring structural and vegetative elements in various combinations. On the micro scale, such systems can shield and buffer “hard” structures that could otherwise not withstand direct open water exposure forces. On the macro scale, wetlands, oyster reefs, dunes, and other natural systems support regional quality of life, contribute to the stable equilibrium of fragile or dynamic landforms, and host economic systems based on fisheries, forestry, and tourism. A combined approach is both necessary and also highly desirable for communities facing threats related to sea level rise, land subsidence, increased storm intensity, aging infrastructure, and other factors.
Two detailed case studies will outline how site scale and regional scale infrastructure systems can yield measurable, reliable, and cost-effective flood risk reduction with significant Green Infrastructure components, combined with hard infrastructure. The Lexington DPW project applied a variety of measures to manage stormwater on site up to the 100-year storm event, thereby identifying and addressing potential problems related to local flooding, while preventing increased off-site flood risk. Methods replicated pre-development hydrology and included water harvesting as well as infiltration and evapotransporation. The Greater New Orleans Hurricane Storm Damage Risk Reduction System (HSDRRS) formulated a robust and resilient regional scale infrastructure system after Katrina that factored in trends and uncertainties surrounding climate change, sea level rise, and land subsidence. Recognizing that no hard infrastructure could perform well in the long term without being surrounded and shielded by healthy coastal wetlands and protective landforms such as barrier islands, these functions were considered as core functional elements. Together, the natural landforms, healthy ecological communities, built structures, and operating procedures were capable of mitigating storm damage based upon multiple lines of defense, delivering a sustainable infrastructure solution that can be emulated in many coastal cities facing the need for climate change adaptation.