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Green Infrastructure for Stormwater Management
The UH Sea Grant's Center for Smart Building and Community Design (SBCD) began this site with the goal of educating a wide range of community members on the benefits and uses of green infrastructure (GI). Community planners across the nation have begun to incorporate GI practices into urban centers. As well, much research around the country is going into how GI can maintain and renew watersheds that host urban centers. This site is a way station for planners, policy makers, and interested community members to learn about alternative stormwater management practices and be directed to the right resource to learn more.
What is Green Infrastructure for Stormwater Management
Before (left) and after (right) the installlation of a rain garden at Manoa Elementary.
Green infrastructure (GI), as defined by the Environmental Protection Agency (EPA), is a system of practices that uses or mimics natural processes to infiltrate, evapotranspirate, or reuse stormwater or runoff on the site where it is generated. GI can be varying in scale and design. These practices can either be integrated into the design of new construction or retrofitted to meet post construction stormwater needs. GI can also be the preservation or construction of natural open spaces like parks, wetlands, or forests.
LARGE SCALE: Parks, natural areas, greenways, agriculture, and forest lands.
SMALL SCALE: Green roofs, trees, rain gardens, rain barrels, permeable pavement, creek daylighting, vegetation swales, pocket wetlands, infiltration planters, and vegetation median strips.
Grey infrastructure is what we commonly associate with our built landscapes. Buildings, roadways, and sewer pipes are all examples of grey infrastructures. Green is not meant to completely replace grey. It is a practice that integrates and compliments the hard structures with natural features, as seen in the before and after picture above: a storm drain is retrofitted with a rain garden. Additional grading was added to the site to direct water draining off the roof and terrain into the rain garden. The concrete channel became an overflow measure, allowing
a large volume of stormwater to be infiltrated and used by
plants before entering the stormwater sewer.
Learn More about green infrastructure practices.
Why Green Infrastructure for Stormwater Management?
Public health and community resilience are the overarching concerns that cut across public and private interests. Central to these concerns is how land use impacts water resources. Alteration of land from development can lead to dramatic changes in the way water is stored and transported. Impervious constructed surfaces (asphalt, concrete, rooftops) and compacted earth associated with development create a barrier to the percolation of rainfall into the soil, increasing surface runoff and decreasing groundwater infiltration. Development and intensive land use also causes generation of more pollutants. Increased runoff serves to transports such pollutants directly into waterways, creating nonpoint source pollution. Polluted runoff is now widely recognized by environmental scientists and regulators as the single largest threat to water quality in the United States.
Source: Green Infrastructure: A Landscape Approach
What You and Your Community Can Do
Pavement is a necessary feature of urbanized communities. However, many options are available to municipal officials who are concerned with reducing negative water quality impacts associated with existing or future development. Strategies can be organized into a three-tiered approach which can be summarized as: plan, minimize, and mitigate.
- Plan development based on your community's natural resources
- Minimize impacts through site design
- Mitigate unavoidable impacts by using Green Infrastructure Best Management Practices
One of the main things that can be done on a residential level is to increase the amount of permeable surface on your property. Increasing your homeʻs ability to slow down, spread out, and soak in rainwater can be done by disconnecting impervious surfaces on your property. Disconnecting the impervious surfaces by using good landscaping practices like green infrastructure interrupts the pathways that runoff utilizes to drain off-site. Downspouts can also be disconnected at their base so that rainwater is directed into a rain garden, rain barrel, or yard as seen in the image on the right. Learn more about downspout disconnection from Clean Water Honolulu. To learn more about what can be done on a residential level see the Watershed Handbook for the Residents of Malama Maunalua (pdf), and the Hawaiʻi Residential Rain Garden Manual (pdf).
There are a number of approaches to mitigating the effects of development in our neighborhoods, streams, and beaches. One such approach is integrating GI into site design planning of new developments as well as retrofits. GI is a multifunctional and cost-effective approach to stormwater infrastructure. GI has the potential to provide a wide suite of benefits to the environment, economy, and community.
Stormwater Management in Policy
There are three main federal laws that regulate nonpoint source pollution. The Clean Water Act (CWA) of 1972, the Clean Water Action Plan, and the Coastal Zone Management Act. Both the Clean Water Act and the Clean Water Action Plan direct the state of Hawaiʻi to draft and implement NPS water pollution plans.
The Clean Water Act
The CWA Chapter 4 (§) 402, National Pollutant Discharge Elimination System permits (NPDES) are issued to each county, and authorizes the discharge of stormwater runoff. State of Hawaiʻi Department of Health administers the National Pollutant Discharge Elimination System (NPDES) permits which control water pollution by regulating point sources that discharge pollutants. One way that the NPDES permits control NPS pollution is through the regulation of stormwater drainage systems. In 2015 the NPDES for Municipal Separate Storm Sewer Systems (MS4) permits for the City and County of Honolulu were updated and became affective on February 15th. The update MS4 permits control discharge from construction sites of at least 1 acre and require post construction permanent BMP's. The CWA Chapter 3, 2014 §303(d) and §305(b) requires that states identify recieving waters that have failed to meet water quality standards for their designated uses. Water that fails to meet water quality standards are designated "impaired" and Total Maximum Daily Loads (TMDL) are created to establish a limit on pollutant discharges into the waters. The TMDL's are limits to point and nonpoint pollution. An Intergrate Report and Total Maximum Daily loads are submitted to the EPA every two years.
Learn More about NPDES Permits.
Learn More about impaired waters and TMDL.
Rouse, David C. "Ch. 2, Lanscape Planning, Design, and Green Infrastructure." Green Infrastructure: A Landscape Approach. Vol. 571. N.p.: n.p., 2013. N. pag. Print.