By Rich Anderson
September 25, 2006

Jeffrey Young, Chairman of the Central Coast Regional Water Quality Control Board of California, delivered the keynote address at the Mayors Water Council Summit in Santa Barbara September 14. The Water Quality Control Board guides development in watersheds, and is responsible for protecting water quality. Chairman Young described what low impact development (LID) is, and what public benefits can be derived from employing LID approaches.

LID is a development guidance method that is designed to replicate the natural hydrologic cycle. LID approaches assume that the Earth, in its natural state, has a sponge-like capability that facilitates infiltration of precipitation rather than runoff. One of the obvious benefits of maintaining or enhancing the infiltration capacity of the land is that it recharges groundwater resources, and while doing so, is a cost-efficient way to remove pollutants and avoid groundwater quality impacts. Young told mayors that they are in the best position to make LID happen because cities can control land use development through planning and land use ordinances.

Traditional stormwater management approaches involve a philosophy that advises planners and developers to move “runoff” from point A to point B through pipes and concrete vaults to avoid flooding. The “natural” approach does not seek to send runoff downstream, but instead, allows the natural vegetative state of soils to absorb as much precipitation as possible.

A basic LID design pursues a balance between water storage, retention and infiltration at the source (property footprint). Land use sites should seek to preserve open space instead of installing impervious pavement. Soils should be managed to avoid the compaction that results from using heavy equipment during construction activities. Maintaining or restoring soil density to facilitate infiltration is preferred. Open drainage swales and landscaping to encourage infiltration and even rooftop storage is the preferred approach.

Young discussed the efforts in Seattle as the example to follow. Seattle is spending $4 million per year to encourage and increase natural drainage systems (a LID approach). Increased natural drainage can achieve a number of desired outcomes that yield public benefits. For example, increased infiltration avoids stream, lake and estuary pollution, protects aquatic biota, and avoids channel erosion. It reduces street flooding and lessens the damage to private property and public infrastructure. It can generally reduce the costs and liabilities associated with flooding conditions.

Seattle demonstrated many of these benefits by designing the Street Edge Alternative (SEA) Project (SEA Street). The city reconfigured a street that was prone to flooding incidents. Curbs were replaced with flat cement borders. The paved street borders were replaced with open drainage culvert including loose soils and loose ground cover intermingled with vegetation. The result is an aesthetically desirable neighborhood with enhanced property values in an area that had a history of floods, property damage and general public inconvenience. Seattle boasts a 98 percent reduction in total runoff volume over two years of measurement. Further, the natural drainage design is less costly to maintain than the paved design infrastructure.

Young stated that the biggest obstacle to LID is the “status quo” (That’s not how we do things!). Existing ordinances tend to maximize impervious surfaces in cities, (e.g., wide streets, wide sidewalks, public safety measures for emergency vehicles). The public benefits of less flooding, increased property values, decentralized storm water treatment and water quality protection provide a good argument to reconsider existing ordinances that prevent LID.