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Solution possible for ice jams on Mohawk River

Solution possible for ice jams on Mohawk River

Perhaps plans can be developed to significantly reduce future flood threats
Solution possible for ice jams on Mohawk River
Ice jams up in front of Jumpin’ Jacks in Scotia earlier this year.
Photographer: MARC SCHULTZ

Ice jams up in front of Jumpin’ Jacks in Scotia earlier this year. Allowing ice and water to more easily flow past the Vischer Ferry Dam downstream could help reduce future flooding due to ice jams on the Mohawk.

The ice jam crisis that flooded the Schenectady/Scotia area has passed, for this winter season.

Although this year’s ice jam blockage produced moderate flooding, it was the most severe in several years.

Ice jams occur in streams and rivers of New York every winter.

A thaw or rain event will break loose channel ice, causing it to move downstream as an ice run. The ice will frequently stop and pile up like a dam, creating a backwater pool. When it’s breached it releases a burst of ice and water downstream.

Four factors cause ice jamming in the Schenectady/ Scotia reach of the Mohawk River:

  • The river channel narrows near Freeman’s Bridge;
  • The river makes a sharp bend near the Rexford Bridge;
  • Various man-made features (bridge piers and abandoned structures);
  • The ice sheet that develops on the pool upstream from the Vischer Ferry Dam.

The Mohawk River is not a naturally flowing river.

It is a system of dams that form navigation pools.

The gates in these dams are raised during the winter months to drain the river pools to the river’s natural condition.

That’s true except for the pool behind the Vischer Ferry Dam.

As one drives over the Western Gateway Bridge, Freemans Bridge, or the new Rexford Bridge carrying Route 146 across the Mohawk, we observe this reservoir pool and incorrectly accept the pool as the Mohawk River.

This reservoir pool extends upstream 11 miles, passing the Schenectady/Scotia area, to the area of Lock 8.

What does this mean?

During the winter months, the river velocity slows down significantly, allowing the reservoir pool behind the Vischer Ferry Dam to quickly freeze and develop a thick ice cover.

When a runoff event occurs and river ice begins to move, the ice run frequently stops. This builds up a pool that usually forces a breach in the ice jam. The breach in the ice jam allows the flow of water and ice to continue moving downstream.

However, when the ice run reaches the massive ice sheet formed behind the Vischer Ferry Dam, often the ice run cannot pass and the ice run stops. Ice then quickly begins to pile up, severely blocking the channel.

Too often, the result is a flooding event in the Schenectady/Scotia area.

It is worth being reminded that Schenectady’s greatest flood occurred in March of 1914, the year the Vischer Ferry Dam was completed.

This was an ice jam event that produced a 231-foot flood stage at Schenectady.

Can anything be done to mitigate this threat?

The answer is “yes.”

But the solution will take some doing.

The Vischer Ferry Dam does not have gates that would allow drainage of the reservoir pool.

If the reservoir pool could be partly drained during the winter months, as almost all the other dams in the canal system are, the probability of damaging ice jam floods in the Schenectady/Scotia area would be greatly reduced.

For example: Assume the reservoir pool could be reduced 10 feet during the winter months.

This would result in increasing river velocity that would facilitate an ice run to pass the Schenectady/Scotia reach and form miles downstream or pass through the dam.

If a jam did form, resulting in a backup, the channel would have an extra 10 feet to contain the rising water in the Schenectady/Scotia area.

The New York Power Authority (NYPA) is responsible for the canal system, including the Vischer Ferry Dam.

It is encouraging to learn that NYPA is conducting a preliminary study of the Vischer Ferry Dam. A draft of this study will be available in as soon as four to six weeks.

If our public leaders can understand the impact of this out-of-sight, state-constructed-and-operated structure on the vulnerable high-value, nearby Schenectady/Scotia property, perhaps plans can be developed to significantly reduce future flood threats.

Russ Wege is a retired engineer who lives in Glenville.

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