Summary on points of geological interest

On 15-16 May 2006 people living along the Bear Island stretch of the flooding Suncook River in New Hamshire, some of them sandbagging or otherwise worried about saving property, were to see some amazing things.  Not only did the river cease to further inundate their land but it also began flowing backwards up its channel.  Here for much of the night and well into the day of Tuesday May 16, 2006, the river water actually flowed upstream.  Never before would anybody have seen the river flowing upstream, the water flowing to the north instead of its usual downstream direction.

Very soon, what had been a boiling raging river that was sweeping along past them, carrying the usual sorts of flood debris, was no more.  

What had been witnessed was a major cutoff event.  Similar events must be geologically common, but in the span of a human lifetime they are rare, especially on the scale that happened along the Suncook at Bear Island in May 2006.   The entire cut off stretch of the river did not drain because of small old dams or weirs (dating from 1870-1872) that are on that part of the river course.  The section which did drain became almost "dry" within only 12 hours,  or was left only with shallow pools so that the river channel could be walked or waded across.  In less than a day, two and a half miles of former Suncook River simply disappeared.

 

According to local eyewitness account the river broke out to follow a new shorter course, which without human intervention may prove enduring, through a section of soft sand deposit at a sandpit ( Cutter’s Pit) and the significant erosion and gouging out of a new channel there to effect the course change was completed in only a matter of minutes, around noon on Monday, 15 May, 2006.

The gravel pit site is seen on the topographic map below as a crossed shovels symbol.  The new more linear stretch the river was assuming east of Bear Island cut its channel 'backwards' (upstream) in the pit area.  The gouging out of a new channel across the sand pit area, as sand was quickly washed away, was observed to progress northwards across the site, creating within minutes a 'canyon like' erosion path across the formerly flat pit base (viz. comparative before-and-after photos below).

This summary has been made (by LachlanHunter Associates, Sydney, Australia) as one of a number of river behaviour comparisons during the study of the evolution of the Hawkesbury-Nepean River near Sydney.   The Suncook River is a meandering river, much smaller than the Nepean but aspects of its behaviour may be similar, or instructive, regarding parts of the Nepean's past history.

 

The course shift of the Suncook River in May 2006

Cut off area (Bear Island) and the new course of the river [By Friends of Suncook River].

Sand pit before the river began to cut through there (photo by Brian Lamarsh).

Similar view of the sand pit after the the river cut it (photo by Brian Lamarsh).

The flood water raging through its new channel at the sand pit.

Aerial view of the new river path eroding through the sand pit area.

Part of the new river course below Epsom, running through a former cornfield.

Quiet pools left along the abandonned Bear Island river course.

Another section of the drained river stretch.

State and federal wildlife personnel move in to collect the endangered brook floater

mussel species from the drained river.  

Kim Tuttle, wetlands technician with the state Fish and Game Department of New Hampshire,

holding mussels collected from the abandonned river course.

  (Story "Mussels lose their river home" - by Chelsea Conaboy, Concord Monitor, 23 May, 2006).

 

 

 

Reports of the Mothers Day flood and river cutoff

 

In mid-May 2006, northeastern USA experienced some days of heavy rain and several states declared a state of emergency as people were forced to evacuate by flooding.  Near the New Hampshire town of Epsom, the flooding Suncook River abandoned its meandering course around Bear Island and carved a more direct NE-SW path.  This is believed to be the most dramatic change in a New Hampshire river course in recorded history.  "Suncook," in the language of the Abenaki Indians, means "to the rocks," and rocks are all left behind of the abandonned former stretch of river.  The river, which once flowed around the 112-acre Bear Island, now takes a shorter path via a gravel pit at the upriver point where the cut through took place.

News items about this event may be found on the webpage of the Friends of Suncook River ( http://www.friendsofsuncookriver.org/page12.htm ), at the Concord Monitor newspaper, and elsewhere.

When the Suncook River charted this new course it tore through trees and land, including a gravel and sand pit.  The water carved through peat bogs and tore away the sand pit such that tyre tracks around the rim of the pit now stop at the edge of a cliff that drops at least 20 feet to the murky water below.  Across the sand pit area the new river course carved out a new channel about 40 feet deep and 80 feet across.  Those affected by the shift mostly want the river moved back.  The owner of the Concord Elks Lodge in Epsom, Bob Griggs, wants it moved back for aesthetic reasons.  His restaurant near Route 28 had a porch above the river, where patrons could watch the water run over a dam.  The restaurant was a lumber mill, and the water running through the dam used to power it.  Griggs's porch now looks over an empty riverbed and dry dam.  State scientists were trying to figure out what happened but cautioned that moving the river back would be expensive, if not impossible.  "You have to understand that it's such a unique thing from a societal perspective," said David Wunsch, chief of the New Hampshire Geological Survey. "Geologically, this happens all the time, it just doesn't happen in a lifetime ..... If it happens during your lifetime, you don't know what to do about it".  Eric Orff, a state wildlife biologist with the Fish and Game department, and who lives by the river, said he was most worried about the aquatic life.  His department received reports of dead bass and about 1,100 mussels were being rescued from along the the former riverbed (perhaps formerly the state's biggest population of the endangered brook floater mussel species).  Orff said rivers shift all the time, but not to the degree that the Suncook had just done.  He thinks that the river shifted when its waters overcame a sand and gravel pit barrier.  The owners of that pit, the Cutter family, said they don't even know what they have anymore.  Much of their land, along with the gravel and sand that was on it has gone, washed away by the river.  (Concord Monitor newspaper, June-July 2006).

Although rivers are constantly seeking a straighter route to the sea, decades of gravel mining made it easier for the river to cut through as a big chunk of two sandy hills that once blocked the current course had been hauled away.  Large pits must maintain the 150-foot buffer called for under the state's Shoreland Protection Act.  Enforcement is up to local officials, and it is not clear whether anyone in Epsom monitored the site to see if the law was being followed.

When Susi Von Oettingen, an endangered species specialist with the U.S. Fish and Wildlife Service, 

heard that the Suncook River had changed course her mind turned to the endangered brook floater mussel prefers.  That stretch of the Suncook hadn't ever been surveyed, but Von Oettingen, thought she might find a few.  In the past, Von Oettingen has been excited to find a few dozen mussels together because they are so rare.  When she visited the drained stretch of former river she instead found hundreds.  People from wildlife services and the state Fish and Game Department moved in, rescuing the live ones in plastic bags and bins, to move them to the federal fishery in Nashua.  Only about a foot of water remained in areas where the crew was collecting.  Von Oettingen said the mussels must return to the Suncook River. The Suncook mussels have specifically evolved to the conditions of that river, she said, and their population could be genetically different than brook floater mussels in the Merrimack or other rivers (Concord Monitor, May 23, 2006).  At Nashua fishery the mussels survive on algae shipped as concentrate from West Virginia and diluted in a blender.

 

The river's relocation wasn't necessarily a surprise to Steve Couture, the rivers coordinator for the Department of Environmental Services.Couture.  Rivers don't like sharp directional changes and, in the old channel, the Suncook turned almost 180 degrees just north of the sandpit. A relatively straight line through the pit was "really where the river wanted to go" Couture observed (Concord Monitor, May 23, 2006).  Couture did not know how much river construction would cost, but he said it would be cheaper to leave the river where it is than to put it back.

 

 

 

A description at time of the flood by the Friends of Suncook River

 

 

The Day the Suncook River Flowed Upstream;

During The Great Mother’s Day Flood of 2006!

 

For much of the night and well into the day of Tuesday May 16, 2006 the Suncook River actually flowed upstream from the Old Mill Dam in Epsom during the highest flood in 100 years on the river.  In fact, the river flowed north, in the opposite direction it had flowed since the Ice Age.  Indeed, a half mile section of the Suncook River, immediately upstream of the Old Mill dam, drained during the great Mother’s Day flood of 2006.

A half mile upstream, a breach in the river’s historic banking was  pulling the river into an entirely new channel, and literally would suck the old riverbed dry in less than 12 hours.  Not only did the new channel suck dry the riverbed above the two dams situated at the head of a series of falls that coursed either side of Bear Island, but  it turned two mile-long stretches of  boiling flood waters on either side of the island to dry riverbeds as well.  In less than a day, two and a half miles of the Suncook River simply disappeared!

Local dam historian Al Bickford of Epsom, pegs the construction of the pair of dams, still in place at the island’s north end, at between 1870 and 1872. The NH Department of Environmental Services Dam Bureau names this dam, the Huckins Mill Dam.  Their records show it was reconstructed in 1937 for a saw mill.  This dam has 202 square miles of drainage area with an impounded surface area of 5 acres.  The western section, closest to the old mill, is 98 feet wide with a maximum height of 13 feet.  Most recently, in the 1980’s, the dam was converted to a hydro power unit for a short period.  Then the mill site was converted into the Old Mill Restaurant, and is currently occupied by the Concord Elks Club.

But let’s back up to see how quickly the complexion of the Suncook River changed from a meandering river in Epsom, save for the two sections of the river that bracketed Bear Island.  Instead of meandering, this section of the river tumbled down a series of rapids and falls for most of the length of the mile-long island before rejoining as one at the confluence of the island’s tail. This created the best section of river for trout fishing in Epsom.

 The river sweeps past my house about three miles downstream. For the first time in the twenty-six years I have lived overlooking the river, it didn’t completely freeze last winter, at least by my house.  The snow-less winter and dry spring conditions, that just over a week prior had the sign next to the Epsom Fire Department declaring “No Burning Permits Issued”, also practically put the river into a summer slumber stage.

All that changed with a deluge of rain starting most of the day Saturday.  By evening my rain gauge measured 3 ½ inches.  Our sleeping neighbor was stirring by nightfall.  By Sunday morning, the Flood Warning predictions that seemed so senseless two days before, were looking more ominous by the hour.  The river was rising rapidly.  In fact, I spent much of Mother’s Day helping the neighbor downriver from me sandbag the flood wall he built in 1988 to protect the lower level of his home which sets right at river’s edge.  We hurriedly added a layer of sand bags on top of his three foot high wall.

As we worked through the afternoon, on the opposite side of the eight inch wide wall we were capping, the river was growing in power carrying whole trees and even a whole wall of a structure with cupboards still attached which bobbed by at nearly eye level. The rapidly rising river rose to the top of the wall just as we finished one layer of sandbags.  Then, in what seemed like minutes, the river won and poured through and over the sandbags.  I was soaking wet and exhausted.

By nightfall my rain gauge was full again to the 4 ½ inch level, bringing the total to 8 inches in two days.  (We got two more inches before the end of the rain storm).  And, the once quiet river roared past my house in the darkness.

Monday morning I awoke to a totally different looking river. It was higher than I had ever seen it; the cornfield and meadow below my house were flooded and the river was filled with debris from parts of trees to bottles and unidentified building parts.  The Suncook churned all this material in a boiling rage, and seemed to spit it right at me from a hundred yards away until the 90 degree bend yanked them from my view.  It was awesome!

But not as awesome as what four local folks would witness by late morning.  Local farmer Bill Yeaton relayed to me the next day what he and three others including Ronnie Colby, Chris Paris and Peter Demers watched just as the Suncook River changed course in a matter of minutes by noon on that Monday May 15^th.

By Bill’s description, the event of the century in Epsom was just underway when he arrived at the locally called Cutter’s Pit at the end of Rhodora Drive at about 11:00 AM on Monday.  The Suncook had overflowed its bank a quarter mile above the access road to the pit, flowing through a wetland and boggy area along the edge of the old Suncook Railroad bed before converging on the access road and flowing into the pit.  The flow was picking up dramatically by the minute according to Bill and was soon a raging flood.  It then began to devour the bowels of the sand pit and ripped huge trees and house sized chunks of the pit quickly washing them down the newly formed river.  The river was relentless at tearing at the earth, widening the trough to a hundred feet, then two hundred feet and more as the raging boiling flow gained momentum.  Then the tongue began to devour the sand to the north along the bed of the pit slicing off three hundred foot wide swaths at a time.  Chomping the exposed sand pit as it marched northward within minutes creating a canyon like vision in the once flat sand pit bed.

It was mid afternoon when the current owner of the old mill site, Bob Griggs, first noticed a change in the flow of water that had been pouring six feet high over the top of the dam at the Old Mill.  A huge white pine tree, 60 feet in length, was forced mostly over the dam by the powerful flows on the far side of the dam.  He noticed by midnight that only a small flow was pouring over the dam.  When he last checked at 2:00am, the top of the dam was bare.  The river was retreating upstream, flowing away from the upstream side of the dam face!  By mid morning the water level was two feet DOWN the front side of the dam – as the river continued to flow upstream.  Below the dam the river was waterless, a few foot long rainbow trout were seen flapping in the few remaining pools.  By day’s end the channel immediately above the dam was dropping even faster as its withdrawal hastened, and by Wednesday morning it was nearly possible to walk across the river even above the dam.  The growing vortex less than a half mile above the dam had swallowed all the flood waters.  The Suncook River flowed upstream from the dam until it vanished from the nearly a half mile section to the breach.  The flood raged on in its new channel.

May 18, 2006

Eric Orff

River Road

Epsom, NH