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Remapping the Floodplain
Dan Simon
More
than 640,000 people live within the 56-square mile Pennypack Creek
watershed. Communities at least partly in its floodplain include the
City of Philadelphia, Abington, Bryn Athyn, Cheltenham, Hatboro, Horsham,
Jenkintown, Lower Moreland, Rockledge, Upper Moreland, Upper Southampton
and Warminster.
As the watershed has become more and more developed, the size of its floodplain increased. Seas of asphalt parking lots shed rainwater, sending the runoff into the Pennypack Creek instead of soaking into the ground. With enough extra runoff, the increase in stream flow leads to bigger floods, more often.
Temple University's Center for Sustainable Communities (Ambler) is conducting a 30-month study in order to provide a more detailed, and current, assessment of the watershed's realities.
"The purpose of this study is to do a multi-purpose, multi-faceted study of the Pennypack Creek Watershed," said Dr. Jeffrey Featherstone, director of the Center for Sustainable Communities and an associate professor of Community and Regional Planning. "Among other things, it will re-draw floodplain maps, develop some open space plans, let us do better water quality sampling and to do a storm water management plan for the entire watershed."
Communities in the region are currently working from outdated floodplain maps, some of which are perhaps as much as 40 years old. Not only has the real estate changed, but there's been significant improvement in terrain and mapping technology since then too.
 "We
need a new one because the data on which the old one has been developed
is basically out of date," Featherstone said. "With new technology,
we're better able to predict floods, we have technology that can enable
us to map flood areas more accurately. It's a case of better information,
better technology.
"The nature of the beast has changed significantly. When the original flood plains were mapped, there wasn't as much development in major portions of the watershed, the upstream portions in particular, as in Montgomery and Bucks counties. Now we have a lot more development. With this development, water that used to percolate into the ground, is being run off directly into the creek."
The study will help the communities in the Pennypack Creek watershed better understand the nature of the problems facing them and perhaps provide clues that will make them better prepared for the next serious flood that hits the area.
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