Home » Green Infrastructure and Enhancing Resilience
The US EPA describes green infrastructure as natural resource management interventions that use vegetation, soils, and natural processes to manage water and create healthier environments. At the scale of a city or county, green infrastructure refers to the patchwork of natural areas that provides habitat, flood protection, cleaner air, and cleaner water. At the scale of a neighborhood or site, green infrastructure refers to stormwater management systems that mimic nature by soaking up and storing water.
Green infrastructure is one approach to enhancing resilience in the built environment. Natural and constructed infrastructure, ranging from conserved riparian buffers to rain gardens and permeable pavers can help enhance stormwater management capabilities in ways that reduce vulnerabilities to flooding. In the urban environment, green spaces can also mitigate the urban heat island effect by providing shade. Natural features can also provide habitat for animals in urban and rural areas. When these green spaces are connected, they can provide migration corridors that offer additional benefits to flora and fauna as well as the human communities that rely on these habitats for recreation and the natural resources they provide. Green infrastructure is tool that can support efforts to enhance resilience because it enables resource manages to identity opportunities to reduce risk through natural interventions. The US EPA details numerous best management techniques, or “integrated management practices” to manage stormwater here.
Protecting open spaces and sensitive natural areas within and adjacent to developed spaces can mitigate the water quality and flooding impacts to communities. Natural areas that are particularly important in addressing water quality and flooding include riparian areas, wetlands, and steep hillsides. Conservation activities can complement green infrastructure benefit projects, and land trusts across the country have been leveraging this connection to support planning, acquisition, and restoration efforts.
Green infrastructure is being deployed at several scales throughout the conservation community. At a project level, implementation of “integrated management practices” can mean restoring historical hydrology. For example, in California the Northcoast Regional Land Trust’s Wood Creek Tidal Marsh Enhancement Project focused on removing ditches and reinstalling large woody debris to recreate a historic salt marsh that provides valuable salmon and goby habitat and allow unimpeded tidal flows. Across the country, the Southwest Michigan Land Conservancy has worked to remove vegetation that is uncongenial to infiltration of rainwater; disable on-site drainage ditches that contribute to dewatering of the landscape; and selective removal of trees and brush within overgrown disturbed habitats to control rainwater from sheeting offsite. While such projects can be considered small in scale, by restoring drainage capacities they can provide numerous benefits including flood risk reduction and habitat enhancement.
Efforts to deploy green infrastructure and the benefits these projects yield are often scaleable, and conservation groups across the country are working at a watershed or regional planning levels to enhance the ability of natural systems to respond to changing water regimes that are increasingly resulting in negative impacts. In the Southeast, The Nature Conservancy’s oyster reef reestablishment project in the Winyah-Sewee Conservation Area aims to build and protect salt marshes, reduce erosion, promote water quality, and provide economic benefits to local fisheries. In New York, Scenic Hudson has developed a watershed-wide sea level rise and inundation mapper. This model is being used both to help communities make more informed planning decisions as well as guide acquisition and enhancement efforts by this land trust to ensure their land holdings are able to facilitate marsh migration and greater floods. In California, the Elkhorn Slough Foundation is similarly prioritizing acquisition efforts to help clear and reclaim the floodplains, allowing natural ecosystems to absorb impacts of greater flooding when enabling people to identify risks and relocate out of harm’s way. In Louisiana, the Lake Pontchartrain Basin Foundation’s Comprehensive Management Plan incorporates a “multiple lines of defense” strategy that highlights the importance of integrated management practices wetland restoration in addition to “grey” strategies to address rising sea levels, greater storm surges, and floods.
According to Breece Robertson, the Trust for Public Land’s geographic information systems (GIS) director, climate-smart cities use green infrastructure in four ways. To learn more, view the brief video below. TPL creates “safe, interconnected opportunities to walk or bike; cool down the city by planting trees and creating parks; absorb stormwater to save energy and recharge aquifers; and protect cities through green shorelines.” When appropriate land trusts can facilitate the deployment of green infrastructure on their own land holdings, or can partner with municipalities or other organizations to encourage policies and projects that include green design considerations to build resilience in their management area.
There is no one “best fit” approach, but green infrastructure is increasingly being recognized as an important tool for enhancing the resilience of natural systems and the built environment. By identifying and working towards win-win solutions, land trusts can help communities plan management to promote resilient systems that are able to respond to current and future climate change impacts.
1. Green infrastructure can provide cost-effective flood and coastal protection. In many cases, green infrastructure provides the same level of risk reduction at a lower cost than gray infrastructure because green projects take advantage of the protection provided inherently by natural systems. For instance, tidal wetlands reduce the size and erosive power of waves along the shoreline of an estuary, while floodplains can divert, hold and slow floodwaters, reducing risks to downstream communities. Preserving or restoring wetlands, floodplains and other natural systems can be less costly than building and maintaining structures of rock, steel and concrete. When other benefits—such as the provision of wildlife habitat or ecosystem services like improved water quality—are considered as well, the advantage of green projects can be even greater. Another factor influencing cost-effectiveness is implementation time; green projects, in particular those that primarily involve the protection of an existing natural system, can potentially be completed more quickly than alternatives requiring major construction.
2. Green infrastructure has been demonstrated successfully in a wide variety of settings. Projects from the Central Valley to the Napa River to the mountains and coasts of southern California illustrate the breadth of designs that are being used to address risks in a range of geographies.
3. Green infrastructure can be designed to adapt to changing conditions. Given adequate amounts of space and sediment, natural floodplains, beaches and shorelines can adapt to altered river flows and sea levels and continue to support healthy ecosystems. Well-designed green infrastructure projects can have the same flexibility.
4. Green infrastructure provides multiple benefits. Each case examined for this report provides benefits beyond flood or coastal protection. These benefits include: habitat for fish, migratory birds and other wildlife; increased productivity from farms and fisheries; carbon sequestration; improved water quality; temporary water storage by wetlands and floodplains; recharge of aquifers; support for recreational activities including bird watching, surfing and fishing; increased property values; and jobs and economic activity supported by fisheries, recreation and conservation.
5. Green infrastructure can inspire strong local support. Green projects tend to provide attractive and highly valued community amenities, such as restored river channels, river parkways, and beaches. This factor is critical for raising local funds, which is often a prerequisite for obtaining government and other outside project funding. As an example: In 1995 a $115 million9 “gray” Napa River flood protection proposal from the Army Corps of Engineers was rejected amidst strong local opposition. Two years later, Napa County voters approved a local sales tax increase to fund a “Living River” design, despite its higher projected cost of $163 million.
Read the report: Reducing Climate Risks with Natural Infrastructure