Erosion study to ID river problems

Thursday, December 6, 2012



LYNDEBOROUGH – Fluvial erosion sounds like something out of science fiction, but it is simply the scientific term for the wearing away of soil, vegetation, sediment and rocks from a riverbank and bed during storms and floods.

The Nashua Regional Planning Commission has received a grant from the state Department of Environmental Services to do an erosion hazard study of the Souhegan River and some of its tributaries through next year.

NRPC representative Jill Longval met with selectmen on Nov. 28 to discuss the project, the first of six meetings planned in the Souhegan watershed during the winter.

She said the study, to be done by a professional consultant, would include defined “problem areas” of the brooks as well as an assessment of bridges and culverts.

Souhegan River tributaries in the study include Baboosic, Beaver, Blood, Great Brook, Hartshorn, Stoney and Tucker brooks.

North Lyndeborough is also in the Piscataquog River watershed, so the town will be advised of that study as well.

Longval said flooding and storm runoff are the natural events most likely to affect New Hampshire residents. In addition to eroding banks, flooding can change the course of the stream, impact roads and structures near the banks, and be costly to repair.

Introductory meetings will be held between now and February, Longval said. In March, letters will be sent to landowners along the brooks, and a public meeting will be held in April.

Field evaluations will take place between May and October.

Results in 2014

Results of the study will be released in January 2014.

“Towns will be kept informed along the way,” she said.

The information can help the towns update their hazard mitigation plans.

Selectman Kevin Boette said he was skeptical, “wherever DES is involved,” and asked, “This looks like a nice thing, but is there a town liability? For instance, do we have to replace the culvert that’s been there for 100 years?”

Longval said no. “DES is sensitive to that (kind of thing). There will be no requirement to implement the study.”

Boette asked if there was penalty for not complying, and Longval said no.

Asked what towns can do with the information, Longval they can incorporate the information when updating their hazard mitigation plans, identify those culverts most likely to be a problem, and prioritize bridges that need to be replaced or repaired, identify roads most likely to be impacted by undersized culverts, and determine future projects.

Resident Tom Chrisenton, formerly with the U.S. Soil Service, asked about landowners who don’t want DES agents on their property.

Longval said, “DES has to honor a landowner’s refusal.”

Chrisenton said landowners should be notified by registered letter, because then a landowner cannot claim to have not been notified.

He also noted, “Bank erosion is not a problem in Lyndeborough, like it is downstream in Milford and Amherst where they have low sand banks.” He added, “You could count (potential) problem areas on one hand.”

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