Just Doing Their Jobs

Philadelphia District dams soften Ivan’s wrath

It would have been much, much worse.

(About $52 million worse, to be exact…)

This was the theme that echoed up and down the Lehigh and Lackawaxen Rivers in the days after September 19, 2004, when Tropical Depression Ivan disgorged its contents over a broad swath of the upper Delaware River watershed.

At water levels not seen since the twin storms Connie and Diane in 1955, the damage was considerable, especially lower down the main stem of the Delaware between Easton and Trenton .

But in areas where a significant percentage of the flow is controlled by Philadelphia District dams—or where other projects such as levees or deepened channels offered protection—the flooding was minor except in isolated cases.

One of the places that did experience some property damage was Palmerton , Pa. , but even there, local officials took the bad news in perspective. Mark Nalesnik, Carbon County 's emergency management coordinator, said Palmerton would have fared worse if the Army Corps of Engineers had not dredged Aquashicola Creek several years ago.

More common was the story of communities like Honesdale, Hawley, Jim Thorpe, Lehighton and Walnutport—as well as the twin cities of Allentown and Bethlehem, where federally built, locally maintained levees provided added protection. “Damages prevented” is a statistic regularly tracked by the Corps for its flood control projects, but for many people it was a very real, substantial and concise term for all that did not go wrong.

The Borough of Hawley on the Lackawaxen, largely protected by Prompton and Jadwin Dams	Lehigh River at Jim Thorpe, running full but contained	Houses along the Lehigh Canal in Walnutport, free of flooding thanks to Walter Dam	Bethlehem Steel Works, high and dry along the Lehigh

“They [the dams] certainly seemed to work,” said Clarke Rupert, a spokesman for the Delaware River Basin Commission, who added that flooding along the Delaware would have otherwise been more severe.

The dams themselves did the work, literally, at Prompton Lake and Jadwin Dam, where the gate openings are fixed and the 40-year-old earthfill structures simply do what they were designed to do. Those who drove by Jadwin soon after the storm were treated to the unusual sight of a full reservoir and a steady discharge of roaring whitewater from what is normally a “dry dam” astride a lazy stream. The downstream citizens of Honesdale and Hawley certainly appreciated how much water would have inundated their streets, cars, homes and businesses if the power of the Lackawaxen River had been fully unleashed.

Jadwin Dam, a “dry dam” under normal conditions, at its highest pool ever recorded	Jadwin Dam at full discharge after the storm

At Francis E. Walter Dam and Beltzville Lake, both of which protect the more densely populated Lehigh Valley, and at Blue Marsh Lake in the Schuylkill subbasin (where this storm was less severe), the gates can be raised and lowered to achieve the desired outflow. The district's water control section in Philadelphia and the dam operators onsite did their usual teamwork to draw down the reservoirs in advance of Ivan, take in the rain to minimize downstream flooding, then release water to restore reservoir capacity once the immediate threat has passed.

Beltzville Lake	Flooding at Beltzville State Park (instead of downstream)	Francis E. Walter Dam, with accumulated debris from upstream	Walter Dam at full discharge after the storm

“The Lehigh River reached flood stage, but major problems along the river valley basically were kept in check thanks to Francis Walter Dam,” reported Ron Gower in the Lehighton Times News.

Not surprisingly, the further you go downstream, the more other tributaries join the river, connected to more runoff sources, and the flood protection dissipates. Compare Allentown and Bethlehem , which experienced only moderate damage, to their hard-hit neighbor Easton , where Bushkill Creek, the Lehigh and Delaware all come together.

There is good reason that the Corps of Engineers now characterizes the primary purpose of these dams as “flood damage reduction” as opposed to the more traditional “flood control.” Let there be no illusion that any person or thing can control, let alone prevent, a flood. Even if that could be accomplished physically, the cost would be way out of proportion to the expected economic benefits, i.e. the damages prevented. On the other hand, if you can at least reduce damages, that could mean the difference between a wet basement and a ruined home, or between cars over water and cars under water.

Now for a look at the numbers (all approximate):

Flood Stage Reductions (in Feet) Downstream of Philadelphia District Dams

Percent of Upstream Drainage Area Controlled by Philadelphia District Dams

Damages Prevented by Philadelphia District Flood Control Projects

Ivan Photo Gallery

09 / 19 / 2004
Aerial and ground views of Delaware River flooding in Yardley

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Photos courtesy of Anthony Bley and Edward Voigt, US Army Corps of Engineers

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Delaware River Basin Commission’s
“REMNANTS OF HURRICANE IVAN”
web page

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