Coastal interdunal marsh/swale  (S1)

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Coastal interdunal marsh/swales are freshwater wetland communities that occur in shallow depressions between sand dunes in the only remaing portion of a dune system in the state. These swales may be shrub or graminoid dominated and are likely very important to amphibaians and other wildlife for breeding, food, and shelter. At one time, numerous swales likely existed along our coast as part of an extensive dune system that occurred in Seabrook and Hampton. The best example of this community type would be a collection of several swales embedded in an intact dune system (conditions lacking in New Hampshire).

Soils are typically seasonally flooded. A thin surface organic layer lies above sandy soils. 

Characteristic vegetation: Dominants vary from swale to swale and include large cranberry (Vaccinium macrocarpon) swales and shore rush (Juncus arcticus) swales. Marginal associates include purple chokeberry (Aronia prunifolia), winterberry (Ilex verticillata), poison ivy (Toxicodendron radicans), and marsh St. John’s-wort (Triadenum virginicum). Cattails may be present, and also invasive species such as purple loosetrife (as in the photo below).


In New Hampshire, the only good example of this community is at The Sands (Seabrook).

Coastal interdunal marsh/swale communities occur as part of larger coastal sand dune systems.