BY JENN McDOWELL

After “100-year” flooding two years in a row, residents in towns along the Suncook River got some answers to questions surrounding the river’s change of course in May 2006, which led to worse flooding in Epsom, Allenstown and Pembroke almost a year later.

In some cases, the answers residents got left them with more questions, some of them questioning the extent of the studies as well as their validity, and others expressing anxiety as the spring melt rushes through the state again.

Researchers performing studies of the Suncook River‘s avulsion, as well as those studying floodplain maps, sediment flow and concentration, dam operations and stream bed changes, presented the latest advancements in their progress at a public meeting on Wednesday, March 26, at Epsom Central School.

Residents also heard multimillion- dollar possible action plans to tame the Suncook in the future. Aside from doing nothing, the least expensive option tops $1.2 million.

“I’m assuming we’re going to find gold or dinosaur bones to pay for this,” said Jack Campbell of Epsom during a discussion of the several plans offered, all of them involving dredging the river bottom to change its character. Researchers Randy Sewall and Peter Walker of Vanasse Hangen Brustlin Inc., contracted by Epsom and the state’s Department of Environmental Services, presented the executive summary of their study, titled “Suncook River Avulsion, Geomorphology-based Alternatives Analysis.”

Sewall, a river specialist, and Walker, an environmental scientist, said their research is ongoing and weeks from being complete, and also that any of the alternatives offered would not completely prevent flooding.

“We’re not here tonight with the final answers,” Walker said. Prior to the May 2006 flood, the river naturally split into two separate channels right after the second Huckins Mill dam, the main river bordering Bear Island on the west and a secondary stream along the eastern border. The two streams joined up just after Bear Island, near Round Pond.

The Suncook changed course in Epsom during the heavy May rains when the rushing water dug a deep trench and blazed a new channel before the Huckins Mill dams, which now carries most of the Suncook’s flow down past Cutter’s gravel pit before joining back with the secondary channel on the east side of Bear Island.

The former main river on the west side of Bear Island all but dried up, and the reduced capacity of the new channel led to worsened flooding in April 2007 and the deposit of more sediment in the downstream towns of Allenstown and Pembroke. Alternative 1 listed in the study is to do nothing, which a few residents at the meeting supported.

Alternative 2 involves installing “cross vanes,” or rock barriers, at strategic points along the river bottom. That plan, which would slow the river’s rush and prevent the bottom from dropping further, would cost about $1,275,000, Sewall and Walker estimated.

This alternative also involves removing sediment deposited downstream near Epsom’s town beach on Short Falls Road.

According to the study, this would prevent another potential avulsion from forming, which could divert a portion of the river into Round Pond.

Another option Sewell and Walker presented was to add to stabilizing the new channel to the cross vane and sediment removal plan. This would require more extensive studies of the new river bottom and a complete reshaping of the stream bottom. That cost was estimated to fall between $1.8 million and $2.1 million.

The study also puts forth the idea of diverting the Suncook back into its original state prior to the avulsion by constructing a dam either by the avulsion site or upstream of it.

The Class B dam would replace the 150,000 cubic feet of sediment eroded off the river bank by the avulsion. This would cost between $4 million and $5.5 million, the study estimated.

Researchers offered pros and cons of the alternatives, mostly for the dam concepts which would greatly impact neighborhoods in the flood plain, would require extensive engineering and of course is the most costly. “Frankly, we see that there’s a lot of risk associated with alternative four,” Sewall said. “This would really be quite an engineering feat.”

Tom Baumeister of Pembroke, concerned about the silt and sludge deposited by his home on Bachelder Road, pointed out the river’s soft, fine bottom

sand in many spots.

“I don’t believe you can stop the silt from going downstream,” he said. “This is why I feel alternatives one, two and three are dead in the water before you even start.”

In terms of cost, it is not yet clear how the three towns would go forward.

Steve Couture of the Department of Environmental Services said any of the solutions would be major undertakings that the federal and state governments would likely contribute to, but added Allenstown, Pembroke, and Epsom residents will need to cooperate with matching funds and public works endeavors to make it happen.

“It’s going to take everyone coming together and contributing what they can,” Couture said. “Any discussion going forward on restoration alternatives will include all three towns.”

Meanwhile, researchers with U.S. Geological Survey are performing sediment studies and mapping the floodplain. Walker said the avulsion study would be wrapped up in the next four to six weeks, which would allow them to make better recommendations about which course of action best suits the Suncook and the residents in the three towns.