PREP Reports & Publications


In the early 1900’s, the majority of coastal salt marshes in New England were ditched as part of an aggressive mosquito control program. In an attempt to eradicate mosquito-breeding habitat, open water areas were drained by a series of ditches excavated in the thick peat soils. Elimination of open water and the unnatural drainage patterns led to degradation of healthy, functional saltmarsh systems and the disappearance of critical habitat for American black ducks, wading birds, shorebirds, shellfish, and fish species, including those that eat mosquito larvae. The practice of mosquito ditching has since been found to have unintended consequences in salt marshes. The artificial ditch systems were found to hold shallow water just long enough for mosquitoes to successfully breed, while prohibiting access to predatory fish species that eat the larvae. Mosquito populations thrived. Ditching also lowered the water table and reduced soil salinities, thus increasing the potential for the invasion of non-native species, such as Phragmites australis (Daiber 1986). Overall, ditching decreased habitat for native species, disrupted the normal hydrologic functions of the salt marsh ecosystem and likely increased mosquito populations. The 23-acre salt marsh addressed in Phase II of this project is part of the larger 42-acre Pickering Brook salt marsh restoration project area (Phase I: 19 acres, Phase II: 23 acres). The Phase II salt marsh is located on the north side of Pierce Point, along Pickering Brook, adjacent to Great Bay in Greenland, Rockingham County, New Hampshire. It is located within the Great Bay Estuary and is identified as a high priority habitat in the Habitat Protection Plan of the Great Bay Resource Protection Partnership. The goal of the Pickering Brook Salt Marsh Restoration Project Phase I and Phase II was to restore a more natural hydrologic regime and provide permanent open water areas on the marsh surface. Restoration activities included the creation and enhancement of surface pools and reclamation of the man-made ditches, while imposing the least impact to the marsh surface. The restoration will also manage mosquito populations, expand recreational opportunities and improve water quality on the marsh Phase II construction occurred under permit number 2002-02056 as amended. Ducks Unlimited contracted with SWAMP, Inc. to complete restoration activities with specialized low ground pressure equipment. Using a specialized wetland excavator, 13 man-made ditches were filled using marsh soils excavated during the enhancement of four permanent pools. To restore the marsh platform of the 23-acre Phase II salt marsh, approximately 470 CY of material was excavated for pool enhancement and then returned to the marsh through the filling or partial filling of existing ditches. Phase II earthmoving activities were completed by April 30, 2004. A monitoring plan was established for Pickering Brook based on a combination of the GPAC and U.S. Fish and Wildlife Service, Coastal Program protocols. Monitoring will provide data necessary to evaluate both restoration approaches and their rate of success at accomplishing goals for this site through the sampling of chosen parameters or indicators. Data analysis and conclusions are beyond the scope of this restoration project and will be conducted under a separate contract. Data was collected with the help of local landowners and volunteers from the Portsmouth Country Club, the Great Bay National Estuarine Research Reserve, and Ducks Unlimited, Inc. Parameters used to assess the success of this restoration include fish use, bird use, mosquito larvae abundance, water levels and salinity, and native vegetation growth. In the ever-evolving world of salt marsh restoration, it is important to incorporate an adaptive management plan into project design. For larger areas, a phased approach may also provide flexibility and benefit restoration efforts at a specific site under specific conditions. The completion of Phase I of the Pickering Brook restoration provided important information and feedback that were used to modify the Pickering Phase II restoration design. The two approaches used to reclaim man-made ditches at Pickering Brook were meant to address the goals and objectives of the restoration plan. Monitoring data collected in subsequent years will be analyzed to comparatively evaluate marsh recovery. Using these two techniques side by side creates an opportunity for study and will provide researchers and land managers with great insight into the response of this salt marsh community to these practices.


Piscataqua Region Estuaries Partnership

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New Hampshire Estuaries Project

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