Climate Change and Stormwater: The Perfect Storm

stormwater-runoffStormwater runoff is a concern year-round, but even more so in the spring when snow is melting and rain is abundant, particularly in humid continental climates. Stormwater starts as precipitation such as snow, sleet, and rain, which lands on natural ground cover such as forests, grass, or gardens. In a natural environment, stormwater soaks into the ground and is filtered by layers of dirt and rock, then finds its way to our groundwater and drinking water supply. Due to urbanization, stormwater in developed areas does not land on natural ground cover but instead washes off roads, driveways, parking lots, rooftops, and other impervious surfaces, becoming stormwater runoff. Stormwater runoff picks up road salt, chemicals, oil, bacteria, sewage, sediment, and garbage, then washes these pollutants into ditches and storm drains, contaminating our streams, rivers, ponds, and lakes. To make matters worse, climate change exacerbates stormwater runoff and contributes greatly to the impairment of surface water supplies.

How Climate Change Exacerbates Stormwater Runoff

flash-flood-stormwater
Climate change will likely bring more intense storms to all areas of the country.

A study by scientists from the National Center for Atmospheric Research in Boulder, Colorado published in December 2016 indicates that climate change will likely bring more intense, frequent, damaging storms to all areas of the country, particularly to the Northeast and the Gulf Coast. In fact, studies show that storms in these areas could become up to five times as frequent and bring 70% more rain if greenhouse gas emissions are not reduced. Storms of this magnitude will likely cause flash floods, landslides, and an overabundance of stormwater runoff – far more than current municipal stormwater systems are designed to handle.

California has recently been experiencing severe drought combined with intense storms.

The study also indicated that regions such as the Pacific Northwest and central United States will likely become drier, but with more intense, extreme rainfall. We have already seen this in northern California, where the Oroville Dam suffered serious damage after drenching rains in February. Prior to these rains, the state had been plagued by severe drought. Rising temperatures increase atmospheric humidity, causing extreme precipitation and an increased risk of flash flooding. And while it may seem counterintuitive, drought only intensifies the problem. Drought leads to less vegetation and more firmly packed soil, both of which inhibit infiltration. When heavy rains follow drought, soil tends to erode, washing remaining plants away as well. Regular, gentle rain is the key to restoring soil, and without it, soil degradation will only intensify.

Managing Increased Stormwater Runoff

Unfortunately, the above-mentioned factors will likely lead to an increase in stormwater runoff and its accompanying problems. Municipal stormwater systems, already faced with increased nutrient regulations, will likely become overwhelmed, resulting in backups, localized flooding, and increased runoff of contaminants such as bacteria and nutrients into waterways.  Also, combined stormwater and wastewater systems overwhelmed by extreme precipitation will release more combined sewer overflows (CSOs) into our rivers, lakes, and streams, degrading water quality and affecting aquatic life. At the same time, drought exacerbates the problem by lowering water levels, leading to more concentrated levels of pollutants in our waterways. These combined factors cause water quality deterioration and create major problems for water treatment plants. Already facing dwindling budgets, municipalities will have difficulty meeting water quality standards if stormwater runoff continues to increase unabated.

Fortunately, successfully managing stormwater runoff is a realistic goal with proper planning and incorporation of best management practices (BMPs). Systems that proactively develop strategies to address stormwater runoff will find themselves far better prepared to manage both increased stormwater and more stringent regulations. Stormwater management strategies include the following:

  1. Rain gardens are a beautiful and sustainable way to manage stormwater.

    Increase the use of Low Impact Development. Low Impact Development (LID), also known as green infrastructure, is a stormwater management approach that maintains natural hydrology during site development. LID minimizes impervious surfaces and utilizes existing natural site features along with conservational controls to manage stormwater. Examples of LID design include bioretention basins, grassed swales, and rain gardens.

  2. Minimize impervious surfaces. Impervious surfaces such as roads, parking lots, and rooftops prevent infiltration. Install pervious pavements on driveways and walkways, stormwater bumpouts on streets, and tree boxes on sidewalks. Also, disconnect impervious surfaces by installing grass or gravel buffer zones. Lastly, plant green roofs and roof gardens to greatly reduce stormwater runoff while enhancing the environment.
  3. Protect and create wetlands. Wetlands are of great value due to their ability to retain water and recharge groundwater. Constructed wetlands provide the same benefit as natural wetlands and help to mitigate water pollution.
  4. White clover is native to New England, drought resistant, and soft under the feet.

    Landscape with native flora. Native trees and plants provide habitat for and attract birds, butterflies, and other beneficial local wildlife, and are acclimated to local rainfall amounts and climate. Unlike turf grass, native plants require very little maintenance because they are naturally resistant to local pests and disease. Because they do not need fertilizers, pesticides, or supplemental watering, they are easy and inexpensive to maintain and are environmentally friendly.

  5. Plant trees. Trees help to manage stormwater by reducing erosion and runoff along streams and waterways. They also help to cool urban areas and improve the air quality.
  6. Separate combined sewer overflows. By separating the collection of sewage and stormwater, overflow of sewer systems and treatment plants during rainy periods prevents the mixing of the surface runoff, which is lightly polluted, with municipal wastewater, which is highly polluted.


In Conclusion

Climate change and stormwater runoff together create the perfect storm for water quality degradation. We are already seeing the effects of climate change on our nation’s infrastructure, and unless we address these complications now, we will likely find ourselves increasingly burdened by boil water orders and expensive water treatment projects. Fortunately, by proactively making some simple and largely inexpensive environmental improvements, we can protect our nation’s water bodies for future generations.

Managing Stormwater in New England with Low Impact Development

10 Best Low Impact Development Stormwater Practices

Stormwater runoff is the number one source of water pollution in the country, and a major threat to clean water in many New England communities. Over the years, we have paved, constructed, and developed the land to the point that the natural landscape is decimated. Where snow, sleet, and rain would normally land on forests and grass and be filtered by layers of dirt and rock, it now washes off parking lots, roads, driveways, rooftops, and other hard surfaces, known as impervious cover, and picks up pollutants such as oil, trash, sediment, bacteria, fertilizer, oil, and road salt along the way. This heavily polluted, untreated water then makes its way into streets and storm drains and subsequently into rivers and lakes that supply our drinking water.

In Texas and Oklahoma this week, we’ve seen the devastating and deadly effects of stormwater runoff. Because the absorbent grasses and dirt have been mostly covered over by pavement and buildings, heavy rains now run off streets, roofs, and driveways, overwhelming drainage systems and, in extreme weather, flooding homes. And in New England, stormwater runoff has not only contributed to water pollution and flash flooding, but also to beach closures, algae blooms, and soil erosion.

What is Low Impact Development?

Low Impact Development (LID), also known as green infrastructure, is a stormwater management approach that maintains natural hydrology during site development. LID minimizes impervious surfaces and utilizes existing natural site features along with conservational controls to manage stormwater. In LID, stormwater is viewed as a resource rather than a waste product, and the site is developed with this key concept in mind. Often, LID replaces traditional stormwater management practices that focus on moving stormwater off-site with curbs, pipes, and ditches.

LID is useful for creating functional, attractive, and environmentally friendly residential, commercial, and industrial sites, and is both sustainable and cost-effective. Some of the benefits include improved water and air quality, reduced stormwater runoff volume, increased natural habitat and recreational space, increased property values, improved groundwater recharge, and community beautification. Below we have compiled a list of ten LID stormwater practices that are most effective in managing stormwater in New England.

rain_garden_stormwater

1. Rain Gardens

A rain garden is typically situated close to the source of runoff and utilizes plants that are able to withstand extremes of moisture as well as excessive nutrients such as nitrogen and phosphorus. By slowing stormwater as it travels downhill, rain gardens provide opportunity for stormwater to infiltrate and also inhibit erosion. While rain gardens provide habitat for wildlife and are an attractive landscaping addition, it’s what’s beneath them that makes them an LID rain garden. Plants and soils are specifically chosen and engineered to clean stormwater by reducing nutrients and overall sediment loads. Multiple rain gardens are often spread over an area, cumulatively controlling the volume and improving the quality of stormwater runoff.

green_roof_fenway_park

2. Green Roofs 

A green roof, also knows as a rooftop garden, is exactly what its name suggests: a roof with vegetation on it. Through evapotranspiration, green roofs remove heat from the surface of the roof and in turn the surrounding air. A green roof is easily installed on any type of building, residential or commercial, and can be as simple as a single layer of groundcover or as intricate as Fenway Park’s extensive vegetable garden. In addition to providing excellent stormwater management and improving water quality, green roofs also provide such benefits as reduced energy use and air pollution, and improved comfort and quality of life.

permeable_pavement_stormwater

3. Permeable Pavement

The link between high levels of impervious surfaces and degraded water quality is indisputable, and most impervious surfaces are paved roadways. Reducing impervious surfaces is one of the key steps in improving any community’s water quality. Permeable, or pervious, pavement is designed to allow water to pass through it into the ground below where it is naturally filtered. Pervious pavement has a myriad of benefits including not only reduced stormwater runoff and replenished groundwater, but also reduction of flooding, pollutants, temperature, roadway ice buildup, and traffic hydroplaning accidents. In New England, special care needs to be taken when utilizing permeable pavement, as there is potential to compromise its effectiveness through plowing and sanding.

grassed_swale_stormwater

4. Grassed Swales

A grassed swale is an open channel designed to manage a specific water quality volume, often along roadsides and parking lots. Stormwater runoff is slowed by vegetation as it flows in these channels, allowing the stormwater to infiltrate and be filtered by the underlying soil. Grassed swales are long and shallow in shape and have plants that are both flood and erosion resistant.

grassed_swale_stormwater

5. Disconnected Impervious Surface (DIS)

DIS is a low-cost, effective way of reducing the volume and flow of stormwater runoff by directing stormwater runoff from impervious areas to graded and vegetated pervious surfaces. DIS is effective for both roofs and paved areas utilizing slightly different designs and provides both infiltration and filtration.

bioretention_basin_stormwater

6. Bioretention Basins

Bioretention basins are landscaped depressions specifically designed to slow and treat on-site stormwater runoff. Typically utilized in parking lots and residential areas, these basins incorporate pollutant removal systems that naturally operate in forests. During a storm event, runoff pools above the mulch and is slowly filtered through the soil beneath before being collected by a perforated underdrain. The clean, filtered runoff is then returned to the storm drain system or local receiving waters.

green_streets_stormwater

7. Alternative Street Design

Alternative street design is mainly effective for new construction and takes into account all aspects of “green streets.” When building a new street, all existing hydrologic functions of the land need to be considered and incorporated in the best possible way into the design. This includes preserving wetlands, buffers, and highly permeable soils while minimizing impervious areas. Typically streets are more narrowly constructed with wide, pervious sidewalks and plenty of vegetated areas.

stormwater bumpout

8. Bioretention Curb Extensions (Stormwater Bumpout)

A stormwater bumpout is a curb extension that extends the existing curb. Typically located either mid-block or at an intersection and composed of a layer of stone that is topped with flood and nutrient tolerant plants and soil, these attractive bumpouts filter stormwater while providing an aesthetic benefit to communities. The bumpout is constructed with an inlet (or curb-cut) that directs stormwater runoff into the bumpout where it can be infiltrated and filtered. The vegetation in a stormwater bumpout is short enough so as not to impact driver sight-lines.

stormwater planters

9. Stormwater Planters and Tree Boxes

Stormwater planters and tree boxes are installed in sidewalks and are designed to manage stormwater runoff from streets and sidewalks. Planters are typically sunken into the sidewalk, rectangular in shape with concrete sides, and lined with a permeable fabric. They are then filled with stone or gravel and topped with soil, hardy plants, and trees. Because they are built down into the sidewalk, runoff is directed into these planters that provide storage, infiltration, and evapotranspiration.

rain cistern stormwater

10. Rain Barrel/Cistern

A rain barrel collects and stores stormwater runoff from rooftops, where it can later be used to water lawns and gardens. To be effective, they must be emptied between storms and utilized by a high percentage of a community’s population. While one rain barrel holds a relatively small amount of water, a large volume of rain barrels can be extremely effective in significantly reducing the amount of stormwater entering a community’s sewer system during storms.

lid-stormwater.net
lakesuperiorstreams.org
nrdc.org
epa.org
lowimpactdevelopment.org
msrc.org
phillywatersheds.org

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