some vegetation. The use of wooden mats to support draglines mini- 

 mizes their damage, though in particularly soft marsh soils, a 

 single traverse by a buggy or dragline may leave tracks readily 

 identifiable for several years. Suspended sediment and nutrient 

 increases that accompany the excavation are of short duration. 



The ditch created by the borrowing of fill remains until refilled. 

 Its effects are dependent upon its location relative to tidal influ- 

 ences. If the ditch is located near a tidally influenced water 

 body, its presence allows some water from the uplands to bypass its 

 normal movement over the marsh surface and thus flow directly to 

 estuarine waters. Therefore, less fresh water flows into the nearby 

 marsh area. The ditch also allows more frequent flooding by an 

 increased quantity of brackish water since there is an open channel 

 connected to tidal waters. As a whole, the amount of surface water 

 flowing onto the marsh increases in the area of influence as a 

 result of the freer flow of estuarine water. In addition, the water 

 is of a higher salinity than previously. 



The increased salinity of water eventually results in an increased 

 soil salt concentration that can have physiological effects on the 

 plants. In addition, the increase in estuarine water input may 

 increase availability of some plant nutrients over the long term. 



While the total quantity of surface water that floods the marsh may 

 increase, the marsh will drain more rapidly because of the presence 

 of the ditch. Thus, after ditching, drainage will become more 

 dependent on tidal influence. Therefore, the average depth of 

 standing water on the marsh decreases while the frequency of submergence/ 

 emergence of plants increases. 



The increase in suspended sediments associated with the borrow pit 

 excavation is short term and affects a ralatively small area. The 

 increase in suspended sediments associated with the increased tidal 

 influence and erosion of the levee banks is of much longer duration. 

 Since there is an increased quantity of brackish water flowing over 

 the surface of the marsh, the suspended sediment load could increase 

 the turbidity and slightly accelerate elevation increase in the 

 marsh. The degree and extent of these phenomena are highly site 

 specific. If the borrow ditch is a great distance from tidal influ- 

 ence, the portions of the above discussion that imply increased 

 inundation frequency must be tempered. 



The decrease in duration of submergence and possible increase in tur- 

 bidity can result in a decrease in production of phytoplankton and 

 benthic algae on the marsh. This decrease in production along with 

 the decreased duration of standing water will decrease the food and 

 cover for aquatic invertebrates and small fishes in the unmodified 



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