Green Infrastructure Strategies

  • Use a retention pond to manage stormwater
    • A retention pond is one of the earliest prototypes of green infrastructure and is now considered a more traditional type of stormwater infrastructure because it has been integrated into gray infrastructure design. It is an engineered stormwater basin designed to store runoff and release it at a controlled rate while maintaining a level of ponded water. Pollutants and sediment loads are reduced as the runoff is retained in the basin. Retention ponds are a very common stormwater management practice and may be designed with sustainable elements to increase water quality and decrease peak discharges. Vegetated forebays may be added to increase sediment removal as well as provide habitat. Another enhancement to traditional stormwater retention ponds is the addition of an iron-enhanced sand filter bench that removes dissolved substances such as phosphorus from runoff.
  • Use a stormwater tree trench to store and filter stormwater runoff
    • A stormwater tree trench is a row of trees that is connected by an underground infiltration structure. At the ground level, trees planted in a tree trench do not look different than any other planted tree. Underneath the sidewalk, the trees sit in a trench that is engineered with layers of gravel and soil that store and filter stormwater runoff. Stormwater tree trenches provide both water quality and runoff reduction benefits.
  • Use bioretention to collect stormwater runoff
    • Bioretention is an adapted landscape feature that provides onsite storage and infiltration of collected stormwater runoff. Stormwater runoff is directed from surfaces to a shallow depression that allows runoff to pond prior to infiltration in an area that is planted with water-tolerant vegetation. As runoff accumulates, it will pond and slowly travel through a filter bed (pictured on the right) where it either infiltrates into the ground or is discharged via an underdrain. Small-scale bioretention areas are often referred to as rain gardens.
  • Use a blue roof to hold precipitation after a storm event and discharge it at a controlled rate
    • A blue roof is designed to hold up to eight inches of precipitation on its surface or in engineered trays. It is comparable to a vegetated roof without soil or vegetation. After a storm event, precipitation is stored on the roof and discharged at a controlled rate. Blue roofs greatly decrease the peak discharge of runoff and also allow water to evaporate into the air prior to being discharged. Precipitation discharge is controlled on a blue roof through a flow restriction device around a roof drain. The water can either be slowly released to a storm sewer system or to another green infrastructure practice such as a cistern or bioretention area.
  • Use extended detention wetlands to reduce flood risk and provide water quality and ecological benefits
    • Extended detention wetlands, such as the one shown in the figure on the right, may be designed as a flood mitigation strategy that also provides water quality and ecological benefits. Extended detention wetlands can require large land areas, but come with significant flood storage benefits. Extended detention wetlands can be created, restored (from previously filled wetlands) or enhanced existing wetlands. Wetlands typically store flood water during a storm and release it slowly, thereby reducing peak flows. An extended detention wetland allows water to remain in the wetland area for an extended period of time, which provides increased flood storage as well as water quality benefits.29 Extended detention wetlands are distinct from the preservation of existing wetlands, but the two practices often are considered together as part of a watershed-based strategy.
  • Use permeable pavement to allow runoff to flow through and be temporarily stored prior to discharge
    • Permeable pavement includes both pavements and pavers with void space that allow runoff to flow through the pavement (pictured left). Once runoff flows through the pavement, it is temporarily stored in an underground stone base prior to infiltrating into the ground or discharging from an underdrain. Permeable pavers are highly effective at removing heavy metals, oils, and grease in runoff. Permeable pavement also removes nutrients such as phosphorous and nitrogen. Soil and engineered media filter pollutants as the runoff infiltrates through the porous surface. The void spaces in permeable pavement surfaces and reservoir layers provide storage capacity for runoff. All permeable pavement systems reduce runoff peak volume.
  • Use underground storage systems to detain runoff in underground receptacles
    • Underground storage systems vary greatly in design. Underground storage systems detain runoff in underground receptacles that slowly release runoff. Often the underground receptacles are culverts, engineered stormwater detention vaults or perforated pipes. One of the benefits of underground storage is that it does not take up additional surface area and can be implemented beneath roadways, parking lots or athletic fields. Underground storage systems are typically designed to store large volumes of runoff and therefore can have a significant impact in reducing flooding and peak discharges.

  • Conduct pilot studies
    • Conduct pilot studies and publish the results and lessons learned to increase awareness and provide specific examples of how alternative stormwater management solutions perform. One specific need is additional examples that quantify infiltration rates in different areas to supplement existing knowledge.
  • Consider using or developing a stormwater model ordinance for green infrastructure
    • An ordinance can help local jurisdictions incorporate climate change projections or green infrastructure incentives into local legislation. For example, the City of Seattle developed a citywide model ordinance for stormwater management using green infrastructure
  • Hire new staff with green infrastructure design and implementation experience
    • This will help to complement existing staff knowledge and expertise.
  • Offer incentives for engineers or contractors to use green infrastructure designs
    • Offer incentives for engineers or contractors to use green infrastructure designs, rather than relying on pipe-based systems.
  • Provide training for municipal staff on green infrastructure
    • Training can help to better equip staff to assess green infrastructure proposals. For example, the U.S. Environmental Protection Agency offers a Green Infrastructure Webcast Series. USEPA and other federal agencies and nongovernmental organizations have formed the Green Infrastructure Collaborative, a network to help communities more easily implement green infrastructure.
  • Publicize a list of "certified or qualified" green infrastructure contractors and engineers
    • Creating such a list can help connect experienced professionals with potential projects that could benefit from alternative design solutions.

  • Collaborate across departments to coordinate the collection of data on the costs and benefits of green infrastructure
  • Conduct research and collect data
  • Consider long-term benefits of green infrastructure in an economic analysis of stormwater management plans
  • Develop tools to assist with quantifying costs and benefits
  • Ensure existing case studies are readily available
  • Identify opportunities to integrate green infrastructure into other projects
  • Incorporate cost and benefit information into tools (e.g., visualization tools) that can support project planning and assist in communications with multiple audiences
  • Present cost statistics in formats that can be shared with colleagues, elected officials and the public
  • Share existing information about how natural systems can be cost-effective and efficient methods of stormwater control and flood mitigation
  • Use cost planning scenarios that are based on real projects for the state or region
  • Collaborate across departments to coordinate the collection of data on the costs and benefits of green infrastructure
    • For example, work with the financial departments to establish an easy tracking and reporting protocol to collect data related to costs and savings of implemented green infrastructure projects. Improve documentation regarding project funding and actual costs. Build a database to inform future projects. Suggest funding organizations incorporate requirements for enhanced financial and impact tracking reporting in project selection.
  • Conduct research and collect data
    • For example what a city spent on repairs and replacement of infrastructure following a storm; job and recreational losses due to damaged or destroyed infrastructure to facilitate improved quantification of the costs and benefits of green infrastructure investments. Provide opportunities for information sharing that are specific to economic valuation. Webinars, workshops, and tools can be used to disseminate existing knowledge and answer questions.
  • Consider long-term benefits of green infrastructure in an economic analysis of stormwater management plans
    • Train local appraisers/commissioners to capture the full value of green infrastructure. Incorporate co-benefits into ROI calculations, such as ecosystem services and quality of life factors.
  • Develop tools to assist with quantifying costs and benefits
  • Ensure existing case studies are readily available
    • Examples that cover a range of municipalities with different budgets and populations are helpful for local practitioners to find and consult studies that are similar to their own communities.
  • Identify opportunities to integrate green infrastructure into other projects
    • This can include projects where green infrastructure provides a co-benefit with little to no added cost (e.g., providing Americans with Disabilities Act [ADA]-compliant sidewalk access, adding a swale for pedestrian protection that also collects rainwater).
  • Incorporate cost and benefit information into tools (e.g., visualization tools) that can support project planning and assist in communications with multiple audiences
  • Present cost statistics in formats that can be shared with colleagues, elected officials and the public
    • Develop communication materials that can be used in conversations with different audiences (e.g., use common terminology to help nontechnical stakeholders better understand the value of green infrastructure).
  • Share existing information about how natural systems can be cost-effective and efficient methods of stormwater control and flood mitigation
    • Share information about the current status and the actual costs and values of projects that were implemented 10 or 20 years ago. Show how benefits and ROI have been realized through formats including videos or other readily accessible modes of communication.
  • Use cost planning scenarios that are based on real projects for the state or region
    • Develop templates that can be used to assess how different green infrastructure methods and projects can work in an area and include cost estimation guidance.

Source Documents

These strategies are adapted from existing U.S. Environmental Protection Agency, Centers for Disease Control and Prevention and other federal resources. Please view these strategies in the context provided by the primary source document: