as additional new canals and wellsites are excavated, the carrying 

 capacity of the intact salt marsh is decreased. Cummulative effects 

 are unknown, and the threshold point (where one additional well will 

 significantly affect the marsh) is obscure. 



Marsh buggy tracks (from surveyor or construction vehicles used in 

 levee-road construction) affect land elevation, creating pathways 

 for increased saltwater inundation and/or freshwater drainage. The 

 depth and number of ruts created by marsh buggies are dependent upon 

 the number of vehicles used and the degree to which they retrace 

 existing paths. In areas that are submerged frequently, the depres- 

 sions are less likely to significantly alter water movement patterns. 

 Hence, confinement of marsh buggy traffic to a narrow corridor in 

 areas near the water's edge may be wise. However, in areas further 

 removed from the estuary, deep ruts resulting from retraced trails 

 would form depressions for the movement of water and, if deep enough, 

 may result in standing bodies of water. The orientation and depth 

 of the depressions determine whether they (1) remain for long time 

 periods and (2) increase or decrease the frequency of inundation of 

 a given area of land. Areas dominated by saltgrass or shore grass 

 may be replaced by stands of smooth cordgrass when the frequency 

 and/or duration of inundation increases. The converse may occur 

 when frequency and/or duration of inundation decreases. The total 

 area affected is site specific and could range from insignificant to 

 highly significant when compared to the total area of salt marsh. 

 Consumers that depend upon smooth cordgrass and its epiphytes for 

 food and/or cover may ultimately increase or decrease. 



The roadway levee blocks normal runoff (on one side of the borrow 

 ditch); the consequences are site specific and may range from imper- 

 ceptible to dire. The borrow ditch intercepts small tidal streams; 

 thus a faster, more direct runoff pattern is substituted for a slow, 

 trickling, dendritic pattern. The ditch also allows an increase in 

 the frequency of inundation. In the area of influence the long-term 

 result will be a greater rate of runoff (decrease in freshwater 

 influences) and an increased frequency of inundation (increase in 

 saltwater influences). Thus, salinity levels will rise in the soil 

 and standing water bodies and vegetation changes will reflect this 

 increase. Nutrient levels may increase over a long time period due 

 to intrusion of nutrient-rich saline waters. On the other hand, if 

 the borrow ditches function more to hasten drainage than to allow 

 intrusion of saline water, a net loss of nutrients may occur (Cope- 

 land and Dickens, 1974). 



The'velocity of the water will increase in both directions along 

 these newly created routes. In the borrow ditch, net export of 

 detritus to the estuary would decrease for two reasons: (1) excava- 

 tion of the borrow has removed the vegetation and (2) the continuous 

 roadway levee interrupts existing small tidal streams which carry 

 the detritus toward the estuary. In marsh buggy depressions, how- 

 ever, export of detritus may be enhanced by creation of these larger 



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