Bioswales are similar to rain gardens, in that they create a space(s) for water to filter and temporarily store during heavy rains before soaking into the ground or draining into water systems, such as lakes, rivers and sewage systems. Like rain gardens, bioswales help reduce or eliminate polluted water runoff during storms, reduce stormwater management costs, and increase the aesthetic value of streets and neighborhoods.

The biggest difference between bioswales and raingardens is that a bioswale is designed to capture larger amounts of water and run it slightly downhill, sometimes in a long ditch or series of sloped rain gardens or "bio retention cells". A rain garden might be the size of a curb extension, but a bioswale might run the length of an entire parking lot, also creating a linear greenway.

Bioswales work really well alongside streets and roads in the planting strip, or where a storm ditch would normally be, or in a median - only now a large portion (or all) of the stormwater has a chance to be filtered and soak into the ground before entering the sewage system or a nearby body of water.

For more information on bioswales click on the links below:

Video: Indianapolis Cultural Trail stormwater system (Streetfilms) -

Video: Vancouver, B.C. bioswale examples and instruction (Univ. of British Columbia) -

Video: Lawrence Tech Univ., Michigan shows how a bioswale works -


Landscaped Curb Extensions

A curb extension (or neckdown or bulb-out or bump-out) protrudes into the street either mid-block or at an intersection, creating a new curb some distance from the existing curb. This traffic calming measure is used to extend the sidewalk into the street, reducing the crossing distance and allowing pedestrians to cross, increasing visibility for drivers and slowing vehicle turning movements. 

Landscaped curb extensions (or storm water curb extensions or vegetated curb extensions or stormwater bumpouts) actually service two awesome purposes: traffic calming AND storm draining. They are most commonly located within street parking lanes, or combined with pedestrian crosswalks at intersections or midblock, or long the side of the roadway, to increase safety along a roadway, reduce storm water overflow and beautify the streetscape.

As in all other storm water techniques that use foliage, select plants based on the geography of the area, anticipated rainfall, and drainage of area feeding the planting. These factors are important to the plants survival and the success of the project.

> Check-out this fact sheet on vegetative curb extensions from the City of Lancaster, Pennsylvania:

> Check out this 2010 video from the Portland, Oregon mayor's office staff describing how landscaped curb extensions (called bioswales here) work:


Planting Strips

Planting strips are storm water techniques that are located between the sidewalk and the street curb, known as the "furniture zone" in urban areas, and are also known as tree lawns, median strips, parking strips and terraces. Planting strips benefit the environment by capturing storm water and reducing strain on sewer infrastructure. They also improve the appearance and character of a neighborhood and soften the hard appearance of otherwise continuous pavement.

Planting strips allow sidewalks to be placed behind a built-in barrier between people and traffic. The strips are normally six to ten feet (two to three meters) wide. A narrow planting strip of just three feet (one meter) is better than nothing, but will not be able to provide all the benefits of a wider strip.

Planting strips can benefit in multiple ways including:

*A place to absorb stormwater runoff when it rains;
*A safety buffer for pedestrians;
*Clearance for vehicle side mirrors;
*Discouraging parking or driving on sidewalks;
*Traffic calming through greening of the streetscape;
*A place to plant trees, flowers and other amenities;
*A wheelchair recovery zone;
*Narrowing the apparent width of a street;
*An area to put fire plugs, utility poles and road signs;
*A place to store snow, trash cans and recycling bins so that sidewalks are not blocked;
*A place to put storm drains instead of in the street, improving bicycling safety;
*A toddler recovery zone.

Planting strip treatments can be simple or elaborate; however just like other storm water treatments, foliage selection to area climate is important to ensure their lifespan.

For more information on how planting strips benefit neighborhoods, check-out "Perils for Pedestrians" fact sheet at


Rain Gardens

Rain gardens are landscaped depressions or holes that allow rainwater runoff from roofs, streets, driveways, sidewalks, trails, parking lots, and compacted lawn areas to soak into the ground as opposed to flowing into storm drains and surface waters, which causes erosion, water pollution, flooding, and diminished groundwater. 

Rain gardens are cost effective in managing stormwater runoff and can double as an attractive addition to the streetscape. For instance, rain gardens can be incorporated into curb extensions, medians, planting strips next to roadways, plazas, play areas, parking lots, roundabouts and traffic circles, and many other places. 

Rain gardens should be designed to be low maintenance, featuring indigenous species. They can be populated with herbaceous perennials, woody shrubs or trees, and annuals. 



No they are not something you throw coins into and make a wish on.

Tree wells are used hand and hand when re-imagining sidewalks and curb extensions, even medians. Their primary functions are for storm drainage, beautification, cooling, shade and air quality. They provide a place where water can drain while also supplying nutrients for adjacent greenery.

In the walkable and bikeable community, trees function in many ways but most importantly they help to create a sense of enclosure and improve safety. Tree wells placed around trees and greenery between the curb and sidewalk help protect people walking from fast-moving motor vehicles. When they are placed with on- and off-street parking they can do much to create a cooling and greening effect that will harmonize with surrounding features. 

This stormwater treatment type can be square, rectangular or circular shaped and are usually 2 to 4 ft wide around the tree. Tree wells near foot traffic have a metal grate around them that will allow water to soak in, yet protect the roots.