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Symposium tackles science of Mohawk flooding

Saturday, March 22, 2014
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The Mohawk River as seen from Water's Edge in Glenville on Friday.
Photographer: Patrick Dodson
The Mohawk River as seen from Water's Edge in Glenville on Friday.

— One hundred years ago Friday, blocks of ice the size of cattle jammed up in the Mohawk River, sending 23 feet of water into Schenectady.

Gazette articles from the time recount wrecked bridges, hundreds of people forced from their homes and several deaths. No Schenectady flood since has equaled the water levels measured on March 28, 1914. Tropical Storm Irene missed the record by a full 7 feet.

On the 100th anniversary, National Weather Service Meteorologist Steve DiRienzo gathered some information about that record-setting flood for this year’s annual Mohawk Watershed Symposium, held Friday at Union College.

“We had a lot of snow that year,” he said, “and a precipitous rise in temperatures.”

A century later, meteorologists and river experts are again watching the lower Mohawk for ice jams. The colder-than-usual winter built up a lot of ice on the Mohawk, and a few big storms blanketed the watershed with enough snowpack to cause problems in a sudden thaw.

Now though, scientists have a lot more tools at their disposal. They learned a lot about ice jams in 100 years and much of that knowledge, among other things, was on display at Friday’s symposium.

Roughly 30 years ago, DiRienzo said a team of U.S. Army cold region engineers starting doing extensive ice research.

“There’s a tactical advantage to knowing how ice works,” he said.

The Army was more concerned about driving tanks across frozen rivers and lakes — less about ice-jam flooding, but much of its research was useful in peacetime.

Specifically it developed an equation in 2002 for estimating ice thickness based upon time and temperature. The character of river beds and flow also is less of a mystery today.

“Imagine the crowd trying to get into a Yankees game,” said Union geology professor and symposium planner John Garver. “Everyone trying to push trough a few turnstiles.”

Garver also brought a poster of ice-jam information to the symposium. Like Yankee Stadium turnstiles, he said the Mohawk River narrows along the Rexford Knolls, creating a natural choke point for ice.

Garver and DiRienzo described a sort of compounding problem in a 15-mile section of the river split by Schenectady.

The Mohawk Valley as a whole, DiRienzo said, acts as a funnel for wind and lake-effect snow. Wind cools the river, forming thick ice. Snow piles on a thick reflective layer, keeping the ice solid.

Then when things do start melting, the natural choke point near Schenectady is worsened by bridges and other man-made infrastructure.

It all adds up to major ice jamming risks. Since 1914, ice jams caused a few floods, including in 1996 and 2007, each causing significant damage. But none were as bad as the 1914 flood, or as frequent as the ones that came before.

In the decades before 1914, ice jams were nearly an every other year occurrence. Things haven’t been as bad since. In part, that’s because the 1914 ice jam was so big that it ruined a few of the especially low-hanging bridges — essentially muscling a route for future ice.

Bridges were eventually rebuilt higher, which slightly eased the situation.

Sadly, 100 years of research doesn’t do much in prevention terms.

“There’s no stopping an ice jam,” Garver said.

Over the years, people have tried dynamite, firehoses and a few other things to get ice moving. On a river the size of the Mohawk, nothing really works. Scientific progress is more about prediction.

In January, U.S. Geological Survey hydrologist Gary Wall installed a video camera between Lock 8 in Glenville and Freeman’s Bridge — near the city’s flood-prone Stockade neighborhood. Dubbed the jam cam, Wall’s installation throws a live feed of the river online.

Wall said video of major ice-jam events could give some insight into long-term warning signs. That said, science has limits.

“There is an element of chance to this,” he said. “Ice could just move through or, by some random occurrence, pile up and cause a big flood.”

In some ways, it’s a roll of the dice. For that reason, the jam cam’s main purpose is short-term warning — to give emergency managers and residents of Schenectady’s most flood prone neighborhoods a bit of warning before the water arrives.

 
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