2.3 Localized change in direction of water flow 



2.4 Possible creation of pathway for increased rate of flow or runoff 

 3. Attribute alterations 



The movement of vehicles and workers over the marsh surface crushes 

 vegetation. The vegetation may be completely uprooted and destroyed in 

 some areas depending upon the soil mositure conditions and the type of 

 transportation that is utilized. The vegetation loss results in an 

 immediate decrease in food and cover for the consumers in the area. The 

 total area affected is usually wery small in comparison to the remaining 

 area of productive vegetation because (1) the gravity meter is quite 

 portable, (2) data stations are not located along predetermined straight 

 lines, and (3) the stations are not regularly spaced. Stations may 

 frequently be reached by boat or by foot; a maximum of one lightweight 

 surface vehicle is necessary for the entire operation. Furthermore, this 

 vehicle need not travel straight-line paths across the marsh surface; it 

 can make maximum use of existing roads or canals. Therefore, the effects 

 of transpiration, evaporation, sediment trapping, fire, available nutri- 

 ents, and peat accumulation are negligible, as the actual affected areas 

 are siery small . 



The above discussion indicates that total vehicular traffic associated 

 with gravity surveys is less than that associated with seismic surveys. 

 Nevertheless, any marsh-surface vehicle may alter local land elevations. 

 Ruts resulting from their use may form depressions for the movement of 

 water and, if deep enough, may result in standing bodies of water during 

 wet seasons. The orientation and depth of the depressions determine 

 whether they (1) remain for long periods of time and (2) alter the water 

 regime of a given area of land by increasing or decreasing the frequency 

 of submergence/emergence, average depth, and duration of submergence. 

 Areas dominated by maiden cane may be replaced by stands of rushes, 

 sedges, canes, or other emergent species when the frequency and/or dura- 

 tion of submergence increases. The converse may occur when frequency 

 and/or duration of submergence decreases. Although the total area 

 affected is site specific, it is usually small when compared to the total 

 area of undisturbed marsh. Because both vegetation types support the 

 same consumers, no significant changes in fauna would be expected. All 

 effects on suspended sediments, nutrients, and runoff are negligible. 



Disturbance factors should be recognized as an important consideration 

 because they extend the effects of the project beyond the boundaries of 

 the immediate site. 



Key attribute alterations 



The alteration which leads to the most significant impacts on the ecosystem 

 is the creation of depressions in the land surface. Although long-term 



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