Low Impact Development (LID)
Filtering Water On-Site with Infiltration
California’s Water Efficiency Landscape Ordinances (WELOs) require new landscapes greater than 2500 square feet to keep or infiltrate rainwater onsite. Rainwater harvesting and grey water collection can fulfill this ordinance.
Infiltration happens when rainwater is directed by a combination of landscape strategies to permeate into the ground. Like rainwater harvesting, infiltration filters rainwater; however, it does not store water on-site. Grey water, which is reusing water for drip irrigation purposes. We have many reasons to encourage rainwater infiltration. Rainwater infiltration protects homes and communities from floods caused by overburdened public waterways; saves aquifers from pollution; and protects surfers and ocean wildlife from fertilizers, pesticides and pollution that run off hardscapes and head for the ocean. Infiltration also protects homes by slowing fast moving water to reduce erosion and sedimentation, increases local water availability by recharging the water table, and cleans water naturally, using vegetation and soil as natural filters. While rainwater collection and graywater systems require plans for concealment to ensure the visual integrity of the landscape. Dry riverbeds add charm to an otherwise soft, lush, green space. Likewise, the waterfall and biological pond below, while perpetually riparian, allow a certain amount of water to be captured and filtered prior to leaving the site. Infiltration is achieved using French drains, percolation pits, creeks and waterfalls or even thoughtful grading.
While rainwater harvesting can be done by a homeowner, the cost of failure with infiltration is high. A poorly constructed dry riverbed, for example, could actually destabilize a slope or flood a home. A beautiful design is not enough. Choosing a knowledgeable, skilled contractor is a must to ensure that both Aesthetics and water diversion are achieved.