2.3 Creation of a water environment about 3 m (8-10 ft) deep 



2.4 Increases in concentrations of suspended sediments and dis- 

 solved nutrients 



2.5 Alteration of normal runoff pathways 

 3. Attribute alterations 



Surveyors and their equipment trample and crush vegetation outside 

 the zone to be excavated, but the area involved is small. Further- 

 more, much of this trampled area may be covered by spoil as the 

 dredging proceeds. A more significant vegetation loss occurs during 

 excavation of a 23-m (70-ft) wide canal and a 0.58-ha (1.2-acre) 

 wellsite and burial of some bordering vegetation by fresh spoil. 

 The area of the latter zone is dependent upon the type of spoil 

 disposal technique. This direct loss results in an immediate de- 

 crease in food and cover for the consumes in the area. The total 

 area affected is usually small in comparison to the remaining pro- 

 ductive vegetation, and the impacts on consumers and detritus 

 accumulation are insignificant. However, as each new canal is 

 excavated, the carrying capacity of the intact ecosystem is de- 

 creased. Cumulative effects are unknown, and the threshold point 

 (where one additional canal will significantly affect the system) is 

 obscure. 



The depth and number of ruts created by vehicles are dependent upon 

 the total number of trips and the degree to which vehicles retrace 

 existing tracks. Deep ruts resulting from retraced trails will 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 surface water and macropore 

 water. In extreme cases, the deep tracks could cross the entire 

 levee or spoil system; this breaching could establish water flows 

 between the systems on either side of the levee/spoil-bank system. 

 Assuming that this major change does not occur, the effects of the 

 depressions are localized in nature. The vegetation in the depres- 

 sions may change to more water-tolerant grasses and sedges, such as 

 Eleocharis spp. and Scirpus spp. 



The depressions allow a faster runoff of surface water in localized 

 areas. However, the long-term effects on sediment loss and nutrients 

 are slight. Increases in turbidity associated with excavation are 

 transient and affect a relatively small area, especially if temporary 

 plugs are placed nearby. Long-term effects are results of erosion 

 of canal banks and fresh spoil deposits; erosion of the former is pro- 



300 



