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Little River Salt Marsh Restoration Project

Little River Salt Marsh Restoration Project

The Little River Salt Marsh Restoration Project in North Hampton and Hampton, New Hampshire has been a huge success from many perspectives.  The great saga of restoring Little River Salt Marsh goes back over 100 years, and is worth reviewing in detail here as a success for ecosystem restoration, locally-led conservation, partnership efforts, and for protecting private property.

The following are included here on the Little River Salt Marsh Restoration Project web site:

Quick Links to other Little River Salt Marsh Resources

The Little River Salt Marsh Restoration Plan and Environmental Assessment is available for download.  This document requires Adobe Acrobat

Little River Salt Marsh Restoration Plan and Environmental Assessment (2.0 MB)

 

Project Summary

View of marsh in 1999, with invading Phragmites.The Little River Salt Marsh is a back barrier marsh lying between Little Boar’s Head in North Hampton and a rocky headland just south of North Shore Road in Hampton.  The original marsh was approximately 193 acres in size, and had deteriorated over many years due to reduced tidal flow to the marsh. Phragmites, cattails, and purple loosestrife had invaded due to the lack of adequate salt water, and flooding of nearby homes was problematic during heavy rains.

Over many many years, residents and agency partners have nearly completed the restoration of the marsh.  The first culvert to restore tidal flow to the marsh was installed in 1999 under Appledore Road, and the second culvert at the north end of the marsh was installed under Route 1A in 2000.  Only one small portion remains.

Ecological Information

The USDA Soil Survey of New Hampshire Tidal Marshes (1974) indicated that originally the marsh was approximately 193 acres in size.  Most of the original marsh had seriously deteriorated and the extent of viable salt marsh greatly reduced.  The marsh had deteriorated because it lacks a connection to the ocean of sufficient size to allow adequate tidal flow to the marsh. Tidal flow is the life blood of a salt marsh. Without tidal flow the overall health of the marsh ecosystem is reduced. 

The characteristic salt marsh plants such as salt meadow cord grass and spike grass, are replaced by the invasive plants Phragmites (see photo to right), narrow leaf cattail, and purple loosestrife.  The lack of an adequate connection with the ocean had also caused serious flooding problems because storm flows from the Little River do not have stable a outlet from the marsh.

View the complete restoration plan and environmental assessment (pdf) for the Little River Salt Marsh.

The Chronology

1992 aerial photo of Little River salt marsh with captionsFor many years, the Little River has had two connections with the ocean.  The southern connection is at the Hampton - North Hampton town line.  This connection, long known locally as the breach,  has been the outlet of the river since at least 1742.  In that year it was used to fix one end of the line separating the towns of Hampton and North Hampton.  At the present time the breach is partially filled with sand which blocks tidal flow to the marsh.  The other connection is a 48 inch concrete culvert which runs through the gap between the second and third (from the north) fish houses at Little Boar’s Head.   This culvert carries twice daily tidal flow to the marsh but its capacity is far below that necessary to support the marsh.  The north culvert is also inadequate for carrying storm flows from the Little River.  See 1992 aerial photo to the right.  (click here for the higher quality version of this aerial photo)


Even under natural conditions, the flow of the Little River is sometimes inadequate to maintain an open connection with the ocean.  During times of low flow, the river silts in, disconnecting the marsh from tidal flow.  Under natural conditions, however, the river eventually ponds enough water in the marsh to break through the dunes again, reconnecting the marsh to the ocean.  This phenomenon is probably the origin of the name breach.  Early on, settlers helped this process along by physically cleaning out the breach. They recognized the importance of tidal flow for salt marsh hay production which began as early as the 17th century and continued until early this century. The first recorded attempt to clear sediment from the breach was in 1780 when residents received permission from the New Hampshire Legislature to open the mouth of the river for the purpose of restoring tidal flow.  

Below are aerial photographs from 1942 and 1992 showing land use changes in and around the marsh. These changes have further degraded the marsh.  In particular the culverts at Appledore Road and Huckleberry Lane have severely restricted tidal flow to the southern portions of the marsh.

Comparison of 1942 and 1992 aerial photos at Little River.

For a higher quality version of this image, click here.

 

View of the 1948 culvert at the "trunk", from the ocean view. To help maintain tidal flow, residents also attempted at various times to create a northern opening (known locally as the trunk,) to the marsh.  In 1890,  the forerunner of the present culvert was installed.  This was replaced by a 30 inch culvert in 1929.  This, in turn, was replaced with the present 48" culvert in 1948 (see photos to the left).

Unfortunately, the creation and subsequent enlargement of the trunk reduced flow through the breach, probably increasing its tendency to silt in.   Up until about 1950, the breach was  regularly cleaned  out.  For most of the time since, it has been  completely blocked with sand and has only been  cleaned out  during times of high water in the marsh.  The increase in the number of buildings around the mouth of the river over the years has made that task increasingly risky.  

NH DOT pictures of the installation of the culvert at the trunk in 1948.Because the breach is essentially an erosive channel through a sand dune, it is very unstable under flood flows.  Once it begins to flow it is subject to rapid erosion and meander.  High flows through the breach during a storm in October 1996 combined with wave action damaged adjacent property and buildings.  The breach has since been partially refilled with sand but the potential for future flooding remains.  During major storms, runoff is forced to pond in the marsh.  Ultimately the river breaks through the barrier dune at some point.  Historically it has broken through at the breach but it could break through at other points.  The only thing that is known with any certainty is that it will break through somewhere.

Flooding problems at the Little River salt marshFlooding has also been a concern to local residents, as an inadequate outlet from the marsh creates flooding during high rainfall events.  The photos to the right show flooding across a local road (top right), and the backup of water to the edge of a residents steps (bottom right).

Residents in Hampton and North Hampton expressed a strong interest in restoring the marsh and solving their flooding problems. Preliminary studies indicate that it may be possible to solve both problems simultaneously.  Properly restoring the salt marsh not  only saved this rare and valuable ecosystem, but will also reduce flooding.

Flood waters approach a residents steps due to inadequate outflow from the marshIn 1998, the U.S. Army Corps of Engineers and the USDA Natural Resources Conservation Service conducted surveys and prepared a computer model of the marsh under various conditions of tides and storm water runoff.  This led to the development of a restoration plan and environmental assessment (pdf) prepared by the NRCS. 

On August 19, 1999, a public hearing (part of the wetland permit process) was held at which time the entire project was explained and comments taken from those present.  In September 1999 the project received state and federal wetland permits for the majority of the project which is located in the town of North Hampton.   The remainder of the project in the town of Hampton is still in the planning stage.

 

Old inadequate culvert at Appledore Road.In January 2000, the first of two planned culverts in the North

The photos to the left show the original culvert under Appledore Road (top left) and the installation of the new 5' x 7' box culvert (bottom left).  The photo below shows the new culvert under Appledore Road.

On July 23, 1998 a public informational meeting was held in the North Hampton Town Hall.  The North Hampton Conservation Commission had invited 150 people, primarily abutters to the marsh.  In attendance at the meeting were 125 local residents and agency personnel.  The plan proposed by NRCS and COE was to install twin 12' concrete box culverts at the location of the present north outlet to the marsh.  Based on hydrologic and hydraulic modeling of the marsh under various conditions of tides and storm flows, these culverts will allow adequate tidal flow to restore the marsh while at the same time solve the current flooding problem.  In straw vote, those present unanimously supported the installation of the proposed culverts.

Installation of part of the new culvert at Appledore Road.

 

 

 

 

 

New culvert functioning properly under Appledore Road.

 

 

 

 

 

 

 

Comparison of the old and new culverts at Little River.

 

Aerial view of the culvert installation at "the trunk" on Route 1A.

 

Senator Judd Gregg and Henry Mixter during a celebration ceremony.

Project Details

 

Beginning excavation from the ocean side of the road.

view of sheetpile needed to keep tide waters out during construction.

Lowering in a section of box culvert.

Construction view of Little River culvert

Data on salinity improvements since installation of the culvert.

 

Celebrations and Awards

First dedication ceremony at Little River in the early 1990s.To the right, the photo shows members of the the North Hampton Conservation Commission dedicating a sign proclaming the Little River Marsh Restoration Project.  The local citizens have been working on the restoration and of this marsh for more than 200 years!  The Natural Resources Conservation Service and the other state, Federal, and private partners were proud to join their efforts.

 

 

Senator Gregg and Henry Mixter at the Little River ribbon cutting ceremony.

Henry Mixter receiving an award from NH Governor Shaheen.

 

Project Partners

Technical and financial assistance: The funding for this project will come from a number of sources including, the Natural Resources Conservation Service, the Towns of North Hampton and Hampton, the Audubon Society of New Hampshire, the U.S. Fish and Wildlife Service, the New Hampshire Coastal Program, NH DOT, Ducks Unlimited, the Fuller Foundation, and private donations. The Selectmen and Conservation Commissions of these towns are actively involved in the restoration effort.  

Local residents have volunteered their time to help this project. Also cooperating in the restoration effort are the New Hampshire Department of Transportation, the U.S. Fish and Wildlife Service, the U.S. Environmental Protection Agency, the Rockingham County Conservation District, the New Hampshire Office of State Planning, and the New Hampshire Wetlands Bureau.

The Selectmen and Conservation Commissions of these towns are actively involved in the restoration effort.