Heavy rains could put region at risk for serious flooding

The schools might be open, the roads might be relatively clear and the sled riding might have… The schools might be open, the roads might be relatively clear and the sled riding might have ceased. However, the effects of Snowpacalypse 2010 could last all the way through spring, as the snow begins to melt and experts worry about flooding.

“It all depends on how it melts,” Rich Kane, warning coordination meteorologist for the National Weather Service, said. “We need to hope for an orderly meltdown.”

Kane said that to avoid serious flooding, the weather needs to remain hovering around freezing. It would be ideal if the thermometer climbs five or 10 degrees above freezing during the day to slowly melt some of the snow. Then, the snow would stop melting at night when the temperatures dip again.

“This would slowly release some of the water into streams and creeks during the day,” Kane said. “And each night, [the snow] would lock back up.”

The timing of the snowstorm doesn’t help, he said. Since it was near the end of winter, we have the possibility of a quick melt.

“We don’t want a rapid warm-up,” Kane said. “The average temperature for March is in the 50s, but we want to stay on the cold side of that.”

While this ideal situation actually played out last week — there was sunshine and relative warmth during the day and freezing temperatures at night — the possibility remains for a significant flood. Kane cited 1936 and 1996 as similar instances when heavy snowfalls contributed to major floods.

“Both floods dealt with rapid snow melt and heavy rainfall,” Kane said.

One major rain event, Kane said, would be okay.

“We have enough snow that would soak it up,” he said, “but the second rain would be the one that releases it all.

The Monongahela River has the most potential for serious flooding because the largest snowpack is in the river’s basin, Kane said. Areas south of the city received the worst snowfall, and the Monongahela’s tributaries, the Youghiogheny River and Cheat River, will all deliver that melted snow through Pittsburgh.

Kane said that 9.8 inches of water are locked up in the snowpack in Terra Alta, W.Va.

Terra Alta is on a mountainous plateau, and its snow melt flows into the Cheat River, which flows into the Youghiogheny. The Youghiogheny flows into the Monongahela. By the time all that water reaches Pittsburgh, it could reach significant flood levels.

“We have to be very, very vigilant,” he said.

In January 1996, this worst-case scenario came true. The Pittsburgh region received more than 20 inches of snow in the beginning of the month.

Then, there was a rapid warm-up. The area also received nearly 3 inches of rain, and when combined with the estimated 4.5 inches of snow-melt runoff, it resulted in flooding that caused an estimated $31 million in damage (which is about $42 million when adjusted for inflation).

While no deaths were reported in the Pittsburgh area, 18 people across the state died from flood-related causes. In total, 33 people across the entire Northeast died because of the great flood of 1996.

Flooding doesn’t just affect the people on land — it has the potential to halt all commercial use of the rivers, including barges.

James McCarville, executive director of the Port of Pittsburgh Commission, said that barge operators and terminal owners will be prepared.

“The industry is very keenly aware of the dangers,” he said. “Companies train for this.”

He said that while most of the barges and equipment are already tied down, the operators and owners need to frequently retie them as the water level rises. It might be a dangerous task, but if it’s not done properly, the ramifications could be catastrophic.

“The biggest danger is if something breaks loose,” he said.

Loose barges could hit a dam or a lock, sending a surge of water downstream. McCarville said that most of these structures are very old and probably won’t withstand a collision.

He said flooding usually only disrupts navigation for a day or two, but there is a concern for loss of production. On a normal day, 600 barges are loaded or unloaded in the port district — this includes all of the navigable rivers of southwestern Pennsylvania. Each barge carries 17 tons of cargo, or about 70 truckloads.

He said that the 200 terminals are privately owned. Therefore, the Port of Pittsburgh Commission does not know what each barge is carrying.

“But if it’s a critically needed commodity, it could pose a problem,” McCarville said.

He isn’t worried so much about the loss of production as he is the potential loss of lives that would likely occur if a barge broke loose and crashed into a dam or a lock. These structures are owned by the federal government and operated by the U.S. Army Corps of Engineers.

Both McCarville and Kane anticipate some flooding.

“It’s just a matter of how much,” Kane said.

City and Pitt officials did not return calls for comment.

Ideal isn’t perfect

While the ideal situation in terms of flooding may be for the snow to slowly melt during the day and then refreeze overnight, this creates another area of concern.

“Most residences have a lot of icicles, and it’s becoming a problem,” Kane said.

Every night when the temperatures drop and the water freezes again, the icicles grow larger and more dangerous.

The Port Authority bus stop Downtown at Market Street and Fifth Avenue was closed this weekend. Icicles surrounded it.

Theresa Whigham takes the 71A to work in Shadyside every day. Last week, she said people at the bus stop on Market and Fifth started to get nervous. The stop sits in front of a building that Whigham said is about three stories high, and icicles lined the edge of the building, right above where people normally stand to wait for the bus — there is no shelter at this stop.

“They were huge, just huge,” she said. “They looked like daggers.”

She said they were at least 3 or 4 feet in length, and there were so many of them that they looked like decorations.

“People kept looking up, and instead of standing under them people started moving toward the curb,” Whigham said.

On Thursday, she said the bus stop was closed, and she had to walk up to Wood Street. The stop was in use again yesterday. Port Authority representatives did not return calls for comment.

Kane said that icicles should be removed only if they pose a danger to people and can be removed safely. He said the best thing to do is to get a long rake, and not just the kind used to rake leaves. He said these sort of rakes are common in areas where snow is a frequent problem — like upstate New York.

“They look like regular rakes but have really long handles,” he said. “That way you can remain on the ground and remove the icicles from a safe distance.”

Ice isn’t just a problem on the edge of roofs, though. Water can get up into the shingles and freeze, which can then cause leaks.

The weight of the ice and snow can also cause collapses.

According to the Post-Gazette, a piece of the roof of a house on Meyran Street collapsed into the living rooms of five Pitt students. A photo shows wet, yellow mush from the insulation covering the furniture and television. The residents could not be reached for comment.

Kane said that snow doesn’t necessarily need to be shoveled from roofs. It all depends on the situation.

If it looks like it could pose a problem to the structural integrity of the house and can be removed safely, then Kane said it would be smart to shovel.

However, snow acts as an insulator on roofs.

“Think of an igloo, where you can take your coat off inside,” he said.

Some snow on the roof is good, he said, but we have too much. Icicles and roof damage might be side effects of a slow, orderly meltdown, but Kane still prefers these problems over flooding.

“Let’s just hope the temperatures climb slowly,” Kane said.