USGS Contributes to Suncook River Flood Study

Reporters: Are you interested in accompanying scientists in the field as they work along the Suncook River? If so, call one of the contacts above about opportunities.
An image of the Suncook River showing the change in its course is available from dnoseral@usgs.gov.

Flood victims along New Hampshire’s Suncook River might be wondering if the river is going to flood again this spring as it has for the past two years. They also might wonder what’s being done to address the problem and restore the Suncook River back to its original channel before the devastating floods of 2006 and 2007.

This spring and summer, crews of scientists from the U.S. Geological Survey (USGS) will conduct field work that includes monitoring stream conditions and collecting sediment samples. The data will become part of a larger study that state and local officials can use to determine the impact of sediments on flooding, fish habitat, and possible corrective actions in the aftermath of the devastating floods that changed the course of the Suncook River.

“There is a concern that the Suncook’s steeper gradient, faster flow, and shallower channel could cause more flooding,” said Robert Flynn, USGS hydrologist who is leading the study. “We are currently collecting sediment data to assess its transport in the Suncook River so that predictions on riverbed stability and movement can be made.”

In general, sediment samples will be collected every two to four weeks from two sites in Epsom and two sites in Allenstown. During spring snow melt and storm events, the sampling will occur more frequently.

Heavy rains in May of 2006 caused flooding in the region and the Suncook River to breach its banks in Epsom, forming a new channel through part of the town, and bypassing an existing one and a half mile section of the river, reducing the river’s total length by about one-half of a mile.

In its new channel, the Suncook Rivers passes through a sand and gravel pit and has buried about 70 acres of agricultural land in Epsom downstream in silt and sand sheets up to 5 feet thick. In the first few months following the floods, an estimated 150,000 cubic yards of sediment entered into the river.

In April 2007, Epsom and Allenstown were flooded once again when heavy rain soaked the region. In response the USGS, with funding from the Federal Emergency Management Agency (FEMA), is assessing characteristics and movement of sediments in the Suncook River from Epsom to its confluence with the Merrimack River in Allenstown.

“FEMA considers this study an important part of our efforts to understand and hopefully, lessen the effects of future flooding in the Suncook River downstream of the where the breach occurred,” said Arthur Cleaves, Regional Administrator of FEMA.

Scientists will use a computerized sediment prediction model to characterize the sediment sources and transport under a variety of flow conditions. The model information will help scientists determine changes in stream bed elevations due to the volume of transported sediment and the potential impact of the transported sediment on future flooding conditions. The study should be completed by the fall of 2009.

FEMA is also supporting USGS hydrologic studies that will be used to help produce mapping of areas of high risk for flooding along the Suncook River from Epsom to Allenstown. Existing flood-insurance maps are now not accurate due to the changes in the channel of the Suncook River.

FEMA and USGS are working with the NH Department of Environmental Services (NHDES) to acquire aerial photography and to develop contour elevation data. This work has been funded via the NH Department of Safety, Bureau of Emergency Management’s Performance Grants to the Town of Epsom with in-kind match being provided by the NHDES via its dam maintenance efforts in the Suncook River Watershed.

“The sediment transport study and flood insurance maps will augment the NHDES grant partnership with the Town of Epsom to determine how to best restore the Suncook River avulsion. The avulsion restoration alternatives will provide us with site specific options and recommendations, while the sediment transport study and flood insurance maps will provide comprehensive information for downstream residents,” said Tom Burack, Commissioner of NHDES.

Representatives of the USGS will present a summary of these studies at the March 26 public information meeting that will discuss on-going Suncook River efforts. This meeting is being hosted by the Town of Epsom and NHDES and will be held at the Epsom Central School, 282 Black Hall Road, from 5:30 – 9:00 pm.

To see on the current flow and stage of the Suncook River, check the real-time stream gage Suncook River at North Chichester on: http://waterdata.usgs.gov/nwis/uv?01089500

Information by the USGS on the floods in New Hampshire in 2005-2007 can also be found at:
USGS Water Resources of New Hampshire and Vermont
http://nh.water.usgs.gov/WhatsNew/index.htm

USGS provides science for a changing world. For more information, visit www.usgs.gov .

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