There's been a lot of news lately - and debate - about new storm-water fees being charged most Baltimore area homeowners. Critics have lambasted them as a "rain tax." City residents have wondered why the fees they'll have to pay are so much higher than their suburban counterparts.
The answer, at least in part, is that urban streams like Baltimore's have been so squeezed, channelized and degraded by development that they lack the ability of more natural streams to absorb and remove at least some of the pollution fouling their waters.
NBC Learn, an educational division of the television network, came to Baltimore recently to report on how the physical alteration of streams in urban areas makes it that much harder for them to handle polluted storm-water runoff. It highlights research on area streams that's being led by Claire Welty, a hydrologist at University of Maryland Baltimore County.
With NBC correspondent Anne Thompson narrating, Welty shows and tells how the loss of vegetation along stream banks and their channeling through concrete culverts deprives them of natural ability to filter out the pollution that causes algae blooms locally and dead zones far downstream in the Chesapeake Bay. The culprits are nutrients - notably nitrates from fertilizer, animal waste and even fallout from air pollution - washed off city streets, parking lots and yards whenever it rains.
Many urban and suburban streams have been converted into glorified storm sewers, their main purpose to prevent flooding by carrying water away from the neighborhood as quickly as possible when it rains. In slower-flowing streams, Welty explains, naturally occurring bacteria can enable chemical reactions that remove at least some of the nitrate pollution from the water. When streams flow faster, she points out, there's not as much time for those natural processes to do their work.
Reversing or offsetting the channelization of streams isn't easy, or cheap, but there are things that can be done. That's another story. This video vividly explains why something must be done if urban and older suburban areas are to enjoy healthier streams and do their part to restore the bay.