At Lock 12 in Tribes Hill, debris-laden floodwater blasted through nearly half of the moveable dam on the Mohawk River.
Similar damage occurred at Lock 11 downstream in Amsterdam, where 3 1⁄2 sections of the dam were blown open. The crushing force swept away two concrete Canal Corporation buildings near Lock 9 in Rotterdam Junction — one during Tropical Storm Irene last week and the other in Tropical Storm Lee this week.
Deep scouring occurred on the Mohawk banks near many of the moveable dam structures in Montgomery and Schenectady counties. Concrete spillways designed to contain the river during normal floods were inundated by the magnitude of water, which quickly eroded new channels around them.
“It’s pretty shocking to see the extent of the damage to the canal system,” said Beth Sciumeca, the executive director of Erie Canalway National Heritage Corridor Commission. “It’s something that is going to require a lot of attention and a lot of funding.”
In all, five of the canal system’s eight moveable dams were damaged. State officials were just starting to get a tally on the devastation from Irene when the next round of flooding from Lee struck Thursday, causing even more damage.
But until the Mohawk recedes there’s no way of knowing exactly how badly the dams at each lock were damaged, how much the repairs will cost or when that section of canal will open again. The only thing clear now is that the dams between Lock 12 and Lock 8 took a pounding.
Force never seen
“These were extraordinary events,” said Howard Goebel, the canal system’s chief hydrologist. “The flows were beyond any levels we’ve seen.”
For example, there was about 6 feet of water cascading over the Lock 10 wall when the Mohawk crested during the prior serious flood in June 2006. This time the water surged more than 13 feet over the same structure during the peak of Irene’s flooding.
“This was a record setting flood, and it was something beyond the ability of anybody to regulate,” Goebel said.
Built during the early 20th century, the moveable dams between Fort Plain and Rotterdam are designed to create navigable channels along the Mohawk during warm weather months. The dams are then raised during the fall to allow the movement of ice or debris during the winter and early spring.
Each section of the dam consists of an upper and lower ‘pan.’ The lower pans are affixed into uprights secured by concrete ‘shoes’ at the bottom of the river; the upper pan can be raised or lowered to regulate the depth of the river.
As Irene approached, canal workers tried to draw down the level of the Mohawk by raising the top pans. Goebel said the draw down started at least two days before the storm hit Mohawk’s sprawling watershed and reduced the river to a depth where it was no longer navigable.
By the time it became clear that Irene would have an impact on the canal system, Goebel said the was no longer any time to raise the system’s lower dam section, a process that must be methodically completed to prevent damage to the structure. He said all of the upper gates must first be lifted and the Mohawk must be drawn down significantly before the lower gates can be pulled out of the river, one lock at a time.
“It’s not something that’s possible when there is many feet of water flowing over top of them,” he said. “The system wasn’t designed to handle that.”
Goebel said the canal system also needed to contend with water being drawn down throughout the region in advance of the looming storm. Crews at the Gilboa Dam were also drawing down water, releasing millions of gallons that ultimately flowed into the Mohawk at the Schoharie Creek confluence.
“There was record flooding because of the record rain and the record releases,” he said.
And there very well may be record damage too. Goebel said getting the canal back into working order is almost certain to be a greater endeavor than after the 2006 flood, due to the scope and magnitude of facilities damaged.
Lock 10 in the hamlet of Cranesville took the brunt of the damage in 2006, although seven sites required attention. Initial estimates placed the total cost of repair to be around $35 million; Lock 10 cost about $9.8 million to repair and remained closed for nearly two months during the peak season.
Canal Corporation Executive Director Brian Stratton said it’s too soon to tell how badly the damage is now. “We are still evaluating damages and determining alternatives, so there is no estimate of the cost of the damages at this time,” he said in a statement released Friday afternoon.
The corridor commission’s Sciumeca said the immediate need along the Mohawk is to tend to the communities that were devastated by the flooding. But she said it’s also important to remember the vital role the canal system plays in the economy along the river.
“There is a larger story here and one that’s going to have an affect next season if the infrastructure isn’t addressed,” she said.
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Categories: Schenectady County