Geography, land use make Pennsylvania flood prone State has more miles of waterways than roads

January 28, 1996|By KNIGHT-RIDDER NEWS SERVICE

Pennsylvania is one of the most flood-prone states in the nation.

Only 186 of its 2,571 communities are regarded by the U.S. Geological Survey as safe from high water.

The rest -- all 2,385 of them -- are sitting ducks.

Blame that on the state's geography and its early settlers. Pennsylvania is home to a trio of major river basins, the Susquehanna, Delaware and Ohio. As a result, the state has more miles of running water (45,000) than it has of state roads (43,000).

These river basins drain land dominated by narrow valleys and steep hills. Sitting downstream from those valleys and hills is much of the state's population -- in towns settled long ago by people whose need for the waterways' transportation and power was so great that they were willing to endure occasional high water.

Thus, when it floods in Pennsylvania -- as it has 47 times in 40 years -- there usually is property damage and sometimes loss of life.

Never had the entire state been hit until last weekend.

"There has never been an occasion of such widespread flooding," said John Comey of the Pennsylvania Emergency Management Agency. "In a normal disaster, conditions are very concentrated."

Entire state affected

All 67 counties felt the effect of the freak weather that began Jan. 7 as a blizzard and ended in a deluge last weekend. All 67 have been declared eligible for federal disaster assistance.

Eighteen people died in the flooding. Gov. Tom Ridge has estimated property losses at $140 million, although early, unofficial estimates by local officials put the tab closer to $200 million.

Most historic floods to strike Pennsylvania, including 1972's benchmark flooding caused by Tropical Storm Agnes, were hurricane-related.

But the January storm is in a class by itself, weather experts say.

"It was a combination of some rather rare events," says Lee Larson, chief of the National Weather Service's Hydrological Research Laboratory in Silver Spring, Md.

In a matter of hours on Jan. 19, a cloudburst akin to those that cause isolated flooding in summer dumped between 2 and 5 inches of rain over all of Pennsylvania. The rain fell on a 30-inch snowpack that blanketed most of the state.

The snowpack "got so soppy that when the rain hit, it was like hitting a saturated sponge; everything ran off," explained John McSparren, chief engineer at the Susquehanna River Basin Commission in Harrisburg. "It was incredible how it all came off at once."

Two floods

The freak conditions actually triggered two floods. The first struck late Friday and early Saturday, Jan. 19-20, on the thousands of tributaries that drain the Delaware, Susquehanna and Ohio watersheds.

Most of these tributaries were choked with ice, which restricted their flows. Ice jams were common; frozen chunks, often the size of cars, smashed anything in their path.

Then came a breather. The rains stopped on Saturday, and water levels on the three big rivers actually dropped slightly. It would prove to be a temporary respite, however.

As soon as the surge in the streams reached the major arteries, the second flood began, with water rising Saturday afternoon and evening at rates that stunned longtime river officials.

"We never saw the river rise so quickly," Mr. McSparren said. In Harrisburg, the Susquehanna rose six to eight feet in one hour on Saturday, he said.

Hardest hit in Southeastern Pennsylvania was Yardley, where the Delaware deposited 4 feet to 5 feet of water. Flooding and ice jams caused damage in Pittsburgh and in several Beaver County towns along the Ohio River.

It was in the Susquehanna River basin, however, where the loss of life and property damage were highest. Fourteen of the 18 reported deaths from the storm occurred in communities drained by the Susquehanna.

Uncontrolled headwaters

The largest of the state's three watersheds, the Susquehanna is notoriously flood-prone. Only 12 percent of its headwaters are controlled by reservoirs, compared with 30 percent on the Delaware.

Flood-control dikes and levees exist in places along the Susquehanna, and they demonstrated their value last weekend. Despite high water, Williamsport and Wilkes-Barre, which have them, stayed dry; Harrisburg, which does not, was flooded.

The newest flood-control project on the river -- and perhaps the last, given the current spending mood in Congress -- is an $86 million levee in Lock Haven. The dike kept the town dry despite waters that crested at 25.8 feet.

The Susquehanna's many tributaries drop rapidly into the shallow branches and sluggish main stem of the river, guaranteeing problems during periods of high water. Those who live along its banks often are squeezed onto narrow flood plains, including at Harrisburg, Wilkes-Barre and Williamsport.

The statistics from last week's flood confirm how dangerous the Susquehanna can be.

Six of the 18 flood-related deaths occurred in Lycoming County, where property damage exceeded $100 million. Four occurred in Lycoming Creek, a small stream just west of Williamsport. Eyewitnesses reported that a four-foot wall of water roared down the narrow creek after an ice jam upstream broke loose on Jan. 19.

"There is devastation all over up there," said Old Lycoming Township Police Chief Salvatore A. Casale. "We have approximately 3 1/2 miles of creek where all the homes are destroyed."

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