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Resilient Tidal Crossings Project

Tidal Stream Crossings

person doing tidal crossing assessment A tidal stream crossing (tidal crossing) is a bridge or culvert that conveys tidal flow below a traveled way, such as a road, pedestrian path, or railroad. When properly designed and maintained, tidal crossings can balance the needs of people and the environment by providing a functional, reliable and safe transportation network that supports the continuous movement of people, goods, and services across coastal communities while allowing adequate tidal flow to maintain healthy tidal marshes.

Resilient Tidal Crossings New Hampshire

In 2018, the NHDES Coastal Program and its partners assessed all known tidal crossings in New Hampshire's 17 coastal communities in accordance with the New Hampshire Tidal Crossing Assessment Protocol Adobe Acrobat Reader Symbol. Tidal crossing assessment data were used to rank and prioritize sites based on structure condition, flood risk, and ecosystem health. The Resilient Tidal Crossings NH Project was designed to better enable community officials and road managers to enact the strategic repair/replacement of tidal crossing infrastructure and to identify high priority restoration and conservation opportunities at tidal crossing sites.

Results of the Resilient Tidal Crossing NH Project are available in a variety of formats, including:

  • Tidal crossing prioritization scores, site data and tidal crossing summary sheets can be viewed on:
  • The entire tidal crossing database can be downloaded from NH Statewide Asset Database Exchange (SADES).

Disclaimer: If you have problems accessing any of these files, please contact Kevin Lucey at Kevin.Lucey@des.nh.gov and we will provide accommodation.

Tidal Crossing Projects

Lubberland Creek Culvert Replacement, Newmarket

In 2015, NHCP provided grant funding to The Nature Conservancy, in partnership with the town of Newmarket, to conduct topographic survey, hydrological and hydraulic analysis, geotechnical analysis, and alternative analysis to develop engineering design drawings for the replacement of a severely undersized and perched culvert where Bay Road crosses Lubberland Creek in Newmarket, NH. The "Lubberland Creek Restoration Bay Road Culvert Assessment," prepared by Wright Pierce Engineers, recommended the replacement of the existing 3-foot round culvert with a 16-foot-wide and 9-foot-tall concrete box culvert, which is designed to accommodate the 100-year storm event while also accommodating predicted sea level rise.

Installation of a new structure is expected in 2019, thanks in part to a NHCP Coastal Resilience Grant.

Links:

Philbrick Pond Drainage Evaluation, North Hampton

Philbrick Pond is a 29-acre salt marsh system that drains a 1-square mile watershed to the Atlantic Ocean through two drainage structures, a culvert beneath Ocean Boulevard, US Route 1A, and a smaller culvert through a 1900 vintage trolley berm. In the 2006 "Mother's Day Storm," drainage restrictions at these two culverts resulted in road flooding that isolated more than 40 homes from access by both personal and emergency vehicles for more than three days. In addition, the Philbrick Pond marsh vegetation has been noted by wetlands biologists for more than thirty years to be severely stressed due to poor drainage resulting in near-permanent inundation.

In 2015, NHCP provided grant funding to the town of North Hampton to conduct a detailed drainage analysis of the Philbrick Pond salt marsh. The "Philbrick Pond Salt Marsh Drainage Evaluation," prepared by CMA Engineers, describes the results of a complex hydrologic and hydraulic evaluation of the salt marsh during various tide cycles, precipitation events, storm surge, and predicted sea level rise. The report also describes the results of a variety of alternatives that were evaluated to improve drainage, reduce flood hazards and improve conditions of the Philbrick Pond salt marsh.

Links:

More Information

For more information about tidal crossings, please contact Coastal Program Habitat Coordinator Kevin Lucey at (603) 559-0026 or kevin.lucey@des.nh.gov

 

 

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