A recent session of breaking up concrete in my back yard the old-fashioned way—sledgehammer in hand—provided me with a few moments to reflect on how my driveway and patio effect the local environment. From the streets and sidewalks running throughout the city to the parking lots and driveways where our cars come to rest, Long Beach has become a large, impenetrable concrete-and-asphalt mat, one bearing little resemblance to land that existed here just a century ago. Modifying the surface of earth in this manner has consequences for the climate and environment, from higher temperatures to greater air and water pollution.

 

Before the Los Angeles Basin became the second-most populated region in the United States, it was a semi-arid desert that transitioned into coastal wetlands. Few signs of that remain: the area has been largely built up and paved over, creating the densest region in the United States. The urban “heat island effect” is a direct result of the built environment. As more space becomes covered with structures and pavement, the heat from the sun is absorbed into the ground and then radiates out again from the earth’s surface. When local temperatures rise, more energy is needed to artificially air-condition homes and businesses. Almost all paved surfaces have greater solar heat retention than natural soil, rock, or clay.

 

The greatest culprits in producing the heat island effect are the black-top asphalt used on most streets, the composition roofing shingles used on most homes, and the hot-mopped tar roofing used on most commercial buildings: these dark surfaces absorb and retain more heat than a natural combination of surfaces. In addition, greater development typically increases the amount of stormwater run-off that can collect and create flooding. As more homes, commercial centers, streets, and parking lots are built, less area remains for rainwater to penetrate into the ground. Instead, storm drains and flood control channels must be used to artificially manage stormwater run-off. In recent years, stormwater management is increasingly being encouraged on a local basis, and more and more new development includes features like bioswales (landscaping that works to absorb and clean surface runoff), retention basins, and detention ponds (both of which can protect against flooding and erosion by temporarily storing water).

 

While some of Long Beach’s land area is covered by a combination of infrastructure and various industrial land uses, residential development makes up the largest category of land use in the city. Because there are relatively few large residential properties, attempting to change the environment through modifying the residential fabric must ideally take place incrementally, as the result of individual homeowners making better choices about their own properties. Every homeowner has the ability to improve the environment through how they treat their driveways, walkways, and patios.  From the design of these areas to the type of material used to pave them, these surfaces can dramatically effect the environment.

 

For instance, the most effective way to both reduce stormwater run off and the urban heat island effect is by increasing surface permeability. I spent the day last weekend doing just that, breaking up portions of concrete that weren’t really needed. Landscaping such areas would further help the environment (by producing photosynthesis and providing a carbon sink), but even the simply act of replacing concrete with gravel allows rainwater to seep into ground and reduces absorption of the sun’s heat.

 

Consider as well your driveway and take a page from the past: the ribbon or “Hollywood” driveways of Long Beach’s older neighborhoods consist of a pair of narrow concrete ribbons. This design was employed in part because concrete was used sparingly in early Southern California home construction. The space between the concrete strips typically was planted with grass, softening the driveway’s appearance in the front yard. This has the added benefit, of course, of increasing permeability, mitigating runoff, and reducing the heat island effect.

 

There are other ways to draw from our past as well: historically, cobblestone roads were made up of tightly placed stones that created a solid surface while allowing water to penetrate into the ground. The modernization of building technology and the need for smoother surface conditions to accommodate greater vehicle speeds resulted in the replacement of cobblestone with asphalt or concrete. While smooth, even surfaces are necessary for modern mobility, driveways can easily be constructed in a cobblestone-like manner, using stone, bricks, or concrete pavers. These materials can also be laid with additional space between them, allowing grass or other ground coverings to fill in the gaps.

 

There is also a growing market for premanufactured products that help create a hard surface with greater permeability and heat reflectivity. One product, Grasscrete, is a cellular concrete system. It has a pattern that looks like a waffle iron and which allows grass to grow between the spaces that puncture through the surface. Within a few weeks of installation, one is left with a field of grass that cars and even heavy vehicles can use. 

 

In recent years there have been advances in building technology that have created more environmentally sustainable poured concrete and asphalt pavement materials. Additives to asphalt can alter its pigment so that it is lighter than the typical “blacktop,” significantly reducing heat absorption. Work to modify the typical aggregate mix of concrete and asphalt has resulted in a series of permeable pavement products that allow water to percolate through the surface as well as reduce the urban heat island affect. There is even a recently-developed additive which, when combined with porous concrete, can absorb CO2.

 

There are many ways you can reduce your driveway and patio’s impact on the local environment, from the simplest to the most technologically sophisticated. Some options will be more appropriate for your conditions than others. As for myself, I still have more concrete to break up in the back yard.