Marsh buggies and draglines associated with canal excavation depress 

 the marsh surface, forming numerous ruts and other depressions. 

 Such depressions may alter existing water flows by channeling 

 surface waters in new directions. Unless such alterations become 

 extensive over large areas, the effects are usually quite localized 

 in the brackish marsh. Tidal amplitude, fluctuation frequency, and 

 flow velocities are generally so small in brackish marsh that altera- 

 tions of water-movement patterns are restricted to relatively small 

 areas. Small open-water bodies may be created, but they are of 

 minor consequence at the ecosystem level. Heavy traffic concen- 

 trated along one route, however, may produce ruts capable of chan- 

 neling surface waters such that freshwater runoff and saltwater 

 intrusions are increased. Intramarsh circulation could be affected 

 as individual water bodies are connected and intermixing occurs. 



Of greater significance to the hydrological regime of the brackish 

 marsh, however, are the dredging of pipeline channels and subsequent 

 spoil deposition. Canals that are adequately backfilled and/or 

 plugged may have localized effects on circulation patterns, but they 

 do not result in long continuous channels and spoil ridges. Water 

 movement patterns remain essentially unchanged following restoration 

 procedures. 



Open unplugged channels bordered by continuous spoil levees generate 

 a complex of interactions which may essentially facilitate changes 

 in the marsh's freshwater-saltwater ratio. Long continuous canals 

 intercept freshwater sheetflow from the uplands and facilitate rapid 

 marsh drainage. Associated spoil levees block or redirect fresh- 

 water sheetflow, preventing its entry into portions of the marsh. 

 Simultaneously, unplugged canals may allow increased intrusion of 

 more saline estuarine waters further inland. The net result is 

 increased water salinity in the marsh. Increased water salinity 

 eventually results in increased soil salt concentrations that can 

 have physiological implications on plant assemblages. Drainage, 

 impoundment, and introduction of stronger tidal forces (if estuarine 

 areas are close enough to affect brackish marsh sites) resulting 

 from pipelining canals and levees may cause extensive changes in 

 such hydrologic characteristics as the duration of water submer- 

 gence, average water depth, and frequency of substrate exposure. 



If drier marsh conditions (reduced length of submergence, shallow- 

 water depth, and frequent substrate exposure) are combined with 

 increased soil salinity, marshhay cordgrass is given a competitive 

 advantage over most other marsh plants. The other major plant 

 group, composed primarily of sedges and rushes, is a particularly 

 significant food source for many waterfowl species and furbearers, 

 primarily the muskrat. Reduction of this plant component decreases 

 the area's habitat suitability for these consumers. Drier condi- 

 tions also result in decreased phytoplankton and benthic algae 

 production as well as decreased food and cover for aquatic inverte- 

 brates and small fish. Secondary consumer groups (predatory mammals 



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