Storm drains like this one in Woodlawn funnel rainfall off streets and parking lots, but often flush oil, dirt and other pollution into nearby streams.
Storm drains like this one in Woodlawn funnel rainfall off streets and parking lots, but often flush oil, dirt and other pollution into nearby streams. (Kenneth K. Lam)

Scientists and others engaged in protecting Maryland's rivers and streams are rising to the defense of the state's storm-water management laws in the wake of Harford County Executive David Craig's call for their repeal.

Craig, a leading Republican candidate for governor in next year's election, said earlier this week that he would push for repeal of at least three state environmental laws, including one requiring property owners in Baltimore City and the state's nine largest counties to pay a fee for reducing storm-water runoff in their communities.


The fee, which Craig and other critics have dubbed a "rain tax," is generally assessed based on the amount of pavement and rooftop that property owners have. Craig contends the fees are inconsistently applied and so steep in places like Baltimore that they'll drive businesses out. But in calling for the fee's repeal, Craig took aim at the scientific basis for focusing on such "impervious surface."

"The impervious surface really doesn't matter," Craig said. "The rain is going to get through somewhere, somehow."

Craig also called for repeal of a 2007 law tightening requirements for new development to limit storm-water runoff, and of a 1984 law limiting development near the shore of the Chesapeake Bay and its tributaries.

Scientists take issue with Craig over his statement questioning the science behind the storm-water fees.

"Mr. Craig's comment flies in the face of all available science on the issue, and more importantly, in the face of common sense," said Andrew J. Elmore, an associate professor at the University of Maryland's Appalachian Environmental Laboratory in Frostburg.

Hye Yeong Kwon, executive director of the Center for Watershed Protection in Ellicott City, said the connection between impervious surface and stream vitality has been established for years now.

Rainfall runs off pavement and roofs when in an undeveloped setting it would soak into the ground, explained Kwon. Her nonprofit center works with local governments and others to curb the effects of storm water.

"These little streams are taking giant loads of water," she said, and the runoff surging into them picks up pollutants on the way, as impervious surface acts as both a collector and conduit of dirt, oil, fertilizer, pet waste and other pollutants.

Generally speaking, streams show clear signs of degradation when 10 percent or more of their watershed is covered by pavement and buildings, Kwon said. Besides increased erosion, streams in more developed watersheds experience declines in the number and types of fish and aquatic insects living there, and changes in the basic chemistry of the water.

In some cases, streams begin to lose ground with even less development. Elmore said recent studies show that having pavement and buildings cover as little as 2 percent of a stream's watershed can hurt brook trout populations, and the pollution-sensitive fish is never found in streams with more than 4 percent of the watershed paved over.

Elmore and Kwon both acknowledge that the costs of reducing storm-water pollution can be daunting, especially for cities and older, more densely developed suburbs. But they contend the effort is critical. Storm-water runoff accounts for about 20 percent of the nutrient pollution fouling the Chesapeake Bay, according to the Environmental Protection Agency, and is the only source still growing.

"The important challenge for science and public policy is to find ways of maintaining economic activity without increasing impervious surface area," Elmore said.