Editor's note: This is the first of a series of three columns to address the runoff problem, overwatering from irrigation and the transporting of fertilizers, pesticides and nutrients to the ocean.
The city of Laguna Beach early this summer mailed a message about changes in lawn watering regulations and a request for help from all of us. Many Orange County cities are being directed by state regulatory agencies to no longer accept runoff from over-irrigation and land watering that drains to the storm drain systems, and the state is requiring cities to amend the municipal codes to prohibit runoff.
Water that flows from our streets to the ocean has become the single largest source of water pollution today. We need to understand that urbanization and life in an urban environment is a source of pollution, and that we are both the source and the cause of pollution.
Runoff has increased as the city has grown and become paved-over with buildings, streets, parking lots and patios. In the early years, 95% of the rain either infiltrated the soil or evaporated and only 5% was runoff. Today, less than half of the rain infiltrates the soil naturally; it cannot soak into paved areas. As impervious surfaces increase, peak runoff velocities increase, base flows and evaporation decreases, erosion happens and water quality degrades.
On average, streets can comprise between 60% and 70% of the total impervious coverage in urban areas and, unlike rooftops, streets are almost always connected to an underground stormwater system. The movement of pollutants in urban runoff is a concern since it contains chemicals and pathogenic organisms that could impair water quality.
Recognizing that streets are the greatest factor in stormwater quality, it is important to employ standards that reduce impervious coverage. While street design is mandated by local municipal standards and it is up to decision makers to allow alternatives, we can take simple steps to reduce or eliminate runoff from our property. We need to define the problem first and then identify opportunities to develop a beach-friendly home. The challenge is to implement measures to control runoff.
The traditional approach views runoff as a flood management problem that needs to be conveyed as quickly as possible to waterways in order to protect the public and property. Consequently, precipitation-induced runoff has been viewed as waste and not as a resource. This approach has been successful at preventing flood damage, but the emphasis on removing the water quickly reduces the opportunity to use this water.
Sustainable stormwater management is an alternative to the traditional piped approach; it promotes onsite collection and conveyance of stormwater from roofs, parking lots, streets and other surfaces to infiltrate into the ground and collect and reuse when possible. Infiltration is ideal for management and conservation of runoff because it filters pollutants through the soil and restores natural flows to groundwater and downstream water bodies.
The infiltration approach seeks to preserve and restore the hydrologic cycle. The idea is to infiltrate runoff into the soil by allowing it to flow slowly over permeable surfaces. The slow flow allows pollutants to settle into the soil where they are naturally mitigated. The reduced volume of runoff that remains takes longer to reach the outfall, and when it empties the pollutant load is greatly reduced.
Here are two easy housekeeping tips to reduce runoff and increase infiltration:
Roofs in the city account for about 20% of the surface area, and rain collected through downspouts drains to the city stormwater system and ends up in the ocean. The solution can be as simple as disconnecting the downspout from the system, directing water to a lawn or garden.
Disconnection is simple, inexpensive and can be easily integrated into landscape design. Materials such as elbows and extensions are available at hardware stores. Maintenance is minimal, and only requires checking periodically that the disclosure location has proper erosion control and drainage.
Downspouts can also be redirected to an underground infiltration pit to allow rainwater to percolate into the ground and recharge our drinking water aquifer, or to rain barrels or cisterns to capture rainwater and use it to water your garden. When using barrels, make sure debris does not clog the system, and screen all vents to prevent mosquitoes from breeding. In areas with soils that drain well, overflow can be directed to landscaped areas.
Driveways can comprise as much as 40% of the city's impervious network. If parking for two vehicles side by side requires a minimum of 400 square feet, the result is 8% of driveway surface on a 5,000 square foot lot or 16% on a 2,500 square foot typical residential lot. If the house itself is compact, the impervious material can become the largest component of impervious coverage on the lot.
Alternative solutions are available to reduce this problem. Driveways can be constructed from a number of materials including pervious pavement. This is a material made of either asphalt or concrete that resembles the conventional materials, but has air space that allows water to pass through the pavement into a crush aggregate and then infiltrate into the ground. The benefit is that it recharges underground water and the sub-grade also filters pollutants. Cleaning the surface once a year maintains porosity. Properly installed, it may last 20 years.
The use of turf-block or unit pavers on sand can create an attractive, low-maintenance, permeable driveway that also filters stormwater. Crush aggregate can also serve as a relatively smooth pavement with minimal maintenance. Paving only under the wheels is another viable option, and repaving the area with permeable unit pavers such as brick or stone can significantly reduce the percentage of impervious area devoted to the driveway.
Studies by the Natural Resources Defense Council and UC Santa Barbara demonstrates that practices that emphasize infiltrating stormwater to recharge ground water supplies in urbanized Southern California and limited portions of the Bay Area has the potential to increase water supplies by as much as 405,000 acre feet per year by 2030. This water saving translates into electricity savings of 1,225.000 MH. This reduces the need for imported water and could prevent the release of 535,000 metric tons of CO2 per year.
By doing this we are reducing the amount of water that the extensive network of underground storm drain needs to handle. A flood control system is designed to control peak flows. Obviously by reducing costly underground infrastructure, we are also reducing the need for future maintenance. Now is the time for adjustments.
The ocean begins at your front door.
GUSTAVO GRAD is a Laguna Beach resident and certified sustainable building advisor. He can be reached at email@example.com.