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Green Infrastructure
 
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Stormwater

Stormwater management is an integral part of everyday life in Broward County … even when it’s not raining. With abundant rainfall and a relatively flat landscape, the infrastructure required for the treatment, storage and management of stormwater runoff is all around us — from neighborhood swales and ponds to lakes and canals. This infrastructure is a necessary facet of the landscape, which has traditionally been designed for the sole purpose of moving and treating stormwater.

As Broward has become built-out, urban densification and redevelopment activities have made innovative strategies to providing stormwater management increasingly necessary. These new approaches, often referred to as green techniques, help mimic natural processes and integrate stormwater management within the landscape to create multi-functional site designs.

These green technologies divert stormwater from traditional storm sewer systems to areas where it can be absorbed and treated by the soil and native vegetation. Designed to retain and treat water on site, these green technologies create water resource benefits that include enhanced aquifer recharge and stormwater recycling.​

Urban Suburban Retrofit

Existing developments, such as business parks, shopping plazas, condominiums or apartment complexes present multiple opportunities to improve water quality, reduce flooding, provide wildlife habitat and increase aesthetic value through the use of green technologies. These green approaches may be retrofitted into existing stormwater management features or constructed on sites lacking stormwater management infrastructure.

Parking lots and roof areas are good places to look for retrofit opportunities. Parking lots generate large amounts of stormwater runoff. Additionally, their high visibility can offer great demonstration value, proving that integrating stormwater management using green technologies can be both functional and aesthetically pleasing.

Existing commercial/industrial sites often make excellent candidates for the incorporation of green infrastructure elements through the stormwater retrofit process. Please see the design features pages for details about green infrastructure practices and the retrofit page for further information.

Green technologies for integrating stormwater management on urban/suburban single-family home sites:

  • ​Naturescape with native vegetation to reduce water and fertilizer use
  • Cisterns/Rain Barrels
  • Rain Gardens
  • Bioretention
  • Bioswales
  • Stormwater Wetlands
  • Green Roofs
  • Permeable Pavements

Retrofit Considerations

Stormwater retrofitting is the practice of updating existing developed sites with modern stormwater management features and practices to improve water quality and reduce flooding. A retrofit project may include a construction or renovation project to incorporate green infrastructure practices on an existing residential, commercial or industrial site. The specific features chosen for a site may vary depending upon available space and land use, but native landscaping or some form of bioretention are typically the easiest to implement and provide increased aesthetic value.

When evaluating an existing developed site for stormwater retrofit, there are several key areas that must be considered:

  • Check whether the site has an existing permit/license for stormwater management with either the local municipality, the local drainage district, the Broward County Development and Environmental Regulation Division or the South Florida Water Management District. If a permit/license exists, check with the regulatory authority to ensure the proposed retrofit is consistent with the existing design. If a permit/license does not exist for the development, check with each regulatory authority to determine the permitting/licensing requirements for the proposed retrofit.

  • Observe the topographic features of the site, including building placement, downspout locations, slopes, pipe inverts and ground elevations to establish the direction of flow and, thus, the best placement for features.

  • Avoid planting trees or other landscape features where their mature trunks or root structure will impede or block flow along the low point of a drainage feature.

  • Avoid placing mulch in or immediately adjacent to the drainage ways. Mulch often floats and can easily be washed into stormwater inlets and potentially impede the flow of stormwater runoff, clog the drainage system, or similarly impact downstream elements of the drainage system.

  • Use root barriers to protect underground infrastructure that may be damaged by root systems.

  • Plant trees so that the estimated mature root zone is at least 5 ft. horizontally from exfiltration trenches (French drains) and from earthen berms, which are designed to impound water.

  • Avoid planting trees on an earthen embankment berm, which acts like a dam. The tree roots may penetrate the earthen embankment and create paths for water to erode the embankment should the roots die and decay. Erosion and failure of the embankment may lead to a release of a significant volume of water onto the adjoining lands.

  • Ensure the placement of landscaping and trees affords sufficient light penetration to avoid killing the ground cover or otherwise destabilizing the ground surface.

  • Develop and implement a maintenance plan to:

    • Routinely remove live and fallen branches and leaves so they do not impede the flow of stormwater runoff or clog the drainage system;

    • Control the detritus created by deteriorating leaves, branches and other plant matter; and

    • Control the reproduction of the trees and understory so the required water storage volume is provided and so the bioretention area may be effectively maintained.

Residential Retrofit​

In Florida’s natural environment, rain can fall onto vegetated land and slowly filter down into the soil. Eventually, this water reaches the water table and can make its way into our groundwater supplies. This is how rain is treated by the natural process and eventually recharges our drinking water supplies.

Rain that falls on hard and impervious surfaces can’t seep into the ground and, instead, runs off into surface waters or onto nearby lands. This rainfall, or stormwater, runoff carries pollutants and contaminants, such as oil, heavy metals, pesticides and fertilizers into our waterways. Additionally, stormwater runoff that can’t percolate down into the ground increases the likelihood of flooding, redirects potential drinking water into local waterways, and can cause loss of habitat due to erosion.

Urban areas throughout Florida and in Broward County have experienced the impacts of increased stormwater runoff associated with large amounts of paved areas. But there is something that we can all do to protect our waterways and our drinking water supply.

Homeowners can take simple measures to reduce the quantity and improve the quality of stormwater runoff from their properties. Swale areas separating sidewalks from roads should be maintained with a soft contour, allowing the collection of runoff from the property. Water collected in the swale is then provided water quality treatment as it slowly percolates through the soil and recharges the aquifer. Walkways created with mulch and pavers, in lieu of pavement, will also reduce runoff and promote aquifer recharge.

Rain gardens help capture and store rainwater. These planted depressions absorb rainwater from impervious surfaces, such as roofs, driveways, walkways and turf areas. Once captured, the stormwater slowly seeps into the ground, instead of flowing into storm drains and surface waters. Some rain gardens reduce pollution flow into waterways by as much as 30 percent.

Rain barrels can also be used to capture and store rainwater. These barrels are positioned at the bottom of rain gutter downspouts to capture rainwater from a home’s roof. The water is then stored for later outdoor use, such as irrigation, car washing or hand watering of plants.

Incorporating native plants into your landscape is an important strategy for improving stormwater management, as well. Native plant beds create a natural environment in which rainwater can percolate down into the ground or slowly move into a water harvesting area, such as a rain garden or pond. Native plants are also specially adapted to Florida’s wet and dry seasons so they use less water, require less fertilizer, and provide habitat for native wildlife.

Existing residential sites often make excellent candidates for the incorporation of green infrastructure elements through the stormwater retrofit process. Please see the Design Features pages for details about green infrastructure practices and the Retrofit Page for further information.

 Green technologies for integrating stormwater management on urban/ suburban single-family home sites:

  • Naturescape with native vegetation to reduce water and fertilizer use

  • Cisterns/Rain Barrels

  • Rain Gardens

Native Landscaping

Proper landscaping is a fundamental component of both the aesthetic and functional relationship between the building and the other elements of a site. The landscape plan should be integrated into the site from design and construction through operation.

 Native landscaping is an integral component of a proper landscape plan and green stormwater technologies, including bioretention, bioswales, rain gardens and green roofs. NatureScape Broward helps people create and maintain attractive, low maintenance and Florida-friendly landscapes that reflect Florida's natural environment. NatureScapes incorporate native plants, landscape best management practices, and green technologies to create sustainable Florida-friendly yards.

 Benefits:

  • Increased infiltration into the soil, which recharges groundwater supplies.

  • A reduction in runoff volume.

  • A decrease in irrigation and fertilization needs, improving water quality.

  • The provision of food, water and shelter for resident and migrating wildlife.

  • An increase in the aesthetic value of yards and neighborhoods

 Design Considerations:

  • Plants must be properly placed with respect to sunlight, drainage, irrigation and space requirements.

  • Plant beds and turfgrass, if used, must be irrigated on different zones.

  • Underground and overhead utilities must be identified and accounted for prior to planting.

Green Roofs

Green roofs are building roofs that are partially or completely covered with plants and soil planted on top of a waterproof layer. They may also include root barriers and drainage and irrigation systems. The purpose of green roofs is to reduce the volume and pollutant load of stormwater runoff.

Distinguished by the depth of their root zone, there are two primary types of green roofs: 1) Extensive green roofs, which provide 4 to 6 inches of root zone and are low maintenance, but they are typically not accessibly to the public and 2) Intensive green roofs, which provide over 6 inches of root zone and provide park-like amenities with public access, but are more expensive and require regular maintenance.

Benefits:

  • A reduction in runoff volume from rooftops through evaporation and absorption.

  • A reduced pollutant load due to filtration provided by soil and root beds.

  • An increased in the aesthetic value and the availability of park-like, recreational amenities.

  • According to the U.S. EPA, green roofs provide the following:

    • Reduced urban heat island effects.

    • Increased thermal insulation and energy efficiency, resulting in lower heating and cooling costs.

    • Increased acoustic insulation.

    • Increased durability and lifespan when compared to conventional roofs.

 

Design Considerations:

  • Must be functional, maintainable and attractive to ensure long-term success.

  • May be installed as part of new construction or retrofitted onto existing structures.

  • Suitable for commercial, industrial and residential applications.

  • Sustainability is enhanced with the use of a cistern system that can provide irrigation needs.

  • May require additional structural reinforcement for support purposes.

  • Choosing the proper landscaping is critical to the performance of a green roof.

  • Select native vegetation with root structures that are compatible to the available depth.

  • Selected plant species that can withstand direct sunlight and dry conditions.

  • Consider maintenance requirements and low maintenance groundcover-type vegetation.

Cisterns & Rain Barrels  

Cisterns and rain barrels are containers used to capture and store stormwater runoff from rooftops. This water can then be used for irrigation or other uses, but not drinking.

Cisterns are larger containers typically used on commercial sites, while rain barrels are smaller containers often used by homeowners. Both can be purchased in home supply stores or can be made from scrap materials.

Benefits

  • Conservation of drinking water supplies because stormwater is more readily available for reuse.

  • Creation of a “no cost” water supply for irrigation.

Design Considerations

  • Cisterns and rain barrels are typically connected to the downspout of a roof runoff collection system. Structures without a roof runoff collection system may require the installation of rain gutters or other similar systems to achieve maximum effectiveness.

  • It is recommended they be cleaned yearly.

  • Periodic checks are required to make sure the cistern or rain barrel is properly sealed to prevent mosquito breeding.

  • The average rainfall per storm event in Broward County is approximately 0.5 inches, which for a 1,500 sq. ft. house would produce 467 gallons of stormwater runoff that could potentially be captured each time it rains.

Bioswales

Bioswales are added to sites to remove silt and pollution from stormwater runoff. Similar to bioretention areas and rain gardens, bioswales are a variation of the traditional grassland swale seen throughout Broward County.

Bioswales consist of depressed land that serves as linear drainage areas. They are shallow, naturally or artificially formed ditches that are filled with vegetation, compost or another natural water filter. They are designed to maximize the time water spends traveling through them, which allows more contaminants to be trapped. Bioswales are different from traditional swales because a fabricated soil bed replaces the native soil with a sand/soil mix that meets permeability requirements. They also include native grasses and plants with deep root structures. These plants slow the flow of water and enhance filtration.

Bioswales are commonly used in parking lots, where water is filtered from the pavement into the depression and travels the length of the lot before being released into the watershed or a storm sewer.

Benefits:

  • An increase in groundwater recharge because more water can infiltrate the soil.

  • A reduction in the volume of runoff water on a site by almost 30 percent.

  • Combined treatment and transportation of stormwater.

  • An increase in the aesthetic value of yards and neighborhoods.

 Design Considerations:

  • Bioswales must be functional, maintainable and attractive to ensure long-term success.

  • While similar in design, bioswales are more linear than bioretention areas or rain gardens, and are designed for conveyance.

  • Only shallow slopes are effective. Steep slopes result in rapid travel and less filtration.

  • Check for or consider installing dams that may enhance pollutant removal.

  • They are primarily used for small sites and may not be effective on larger sites.

  • Choosing the proper landscaping is critical to the performance of a bioswale: 

    • Select native vegetation with deep root structures.

    • Select species that withstand the frequent and substantial water flow. Plants that can tolerate both wet and dry conditions may work best.

    • Consider the flow path to maximize conveyance. Bioswales may be more linear or curvaceous, depending on site characteristics.

    • Design the planting layout to allow for easy access and to facilitate periodic removal of sediments without significant disruption or removal of plant materials.

    • A lack of consideration for these details can lead to failed plantings and site flooding.

​​Bioretention

Bioretention is a vegetated shallow depression where stormwater collects and is allowed to slowly percolate down into the ground. Contaminants and nutrients are removed from the stormwater by special microbes that biologically remove these components or through a filter medium that mimics the natural process. The name refers to the fact that the removed components are held within the system after removal. Each site may feature multiple bioretention areas for the treatments and storage of stormwater runoff close to the sources. Not only are bioretention areas useful in removing contaminants from stormwater, they also add aesthetic value to a property.

Benefits:

  • An increase in groundwater recharge because more water can infiltrate into the soil.

  • A reduction in the volume of runoff water on a site by 35 to 50 percent.

  • The addition of valuable wildlife habitat and, thus, an increase in wildlife.

  • An increase in the aesthetic value of yards and neighborhoods.

  • Better protection against floods.

  • Improved water quality in lakes and canals.

Design Considerations:Considerations:

When installing bioretention areas on a site, be sure to consider the following:

  • Using an underdrain or perforated pipe system on the bottom of the filter bed may encourage water to be drawn further underground between storm events.

  • To ensure long-term success, the bioretention site should be functional, maintainable and attractive.

  • Multiple bioretention areas close to the sources of pollution may result in lower-impact designs.

  • Bioretention cells are most beneficial on small sites less than 5 acres.

  • Proper landscaping and maintenance is critical to the performance of a bioretention area: 

    • Select native vegetation with habitat value.

    • Select species that can withstand frequent and substantial waterflow. Plants that tolerate both wet and dry conditions work best.

    • Consider planting a combination of herbaceous materials and trees and shrubs.

    • Design the planting layout to allow for easy access. Also, make sure it allows for periodic removal of sediments without significant disruption — or the removal — of plants.

    • A lack of consideration for these details can lead to failed plantings and increased flooding.