The potential for re-establishment of natural configurations and flow 

 patterns after site closure are totally dependent on the degree of change 

 to the hydraulic processes characteristic of the river system. Long-term 

 effects can be expected where major changes to the stability of channels 

 occur. The major terrestrial effect of scraping resulted where deep scrapes 

 occurred in areas immediately adjacent to the channel. Channel flow often 

 diverted through these depressions and caused year-round ponding which 

 retarded the re-establishment of vegetation. These deep scrapes usually were 

 inadequate as quality habitat for waterfowl and shorebirds and unsuitable 

 for fish. To minimize short- and long-term effects, scraped sites should not 

 be excavated beyond certain depth limits. These restrictions are discussed 

 in the Guidelines Manual. 



The effects of scraping operations on the scenic quality of a braided 

 floodplain can be minimal if the material sites are restricted to the active 

 floodplain. Where banks and vegetated areas are altered, significant effects 

 can be anticipated. In split and single channel systems the establishment of 

 a braided configuration in the disturbed area produces an unnatural condi- 

 tion in the floodplain, thus affording a visual contrast. Properly located 

 scraping operations that avoided or minimized disturbances to the hydraulic 

 characteristics of a river, minimized long-term environmental change. How- 

 ever, where sites were poorly located and caused significant changes to the 

 channel hydraulics, major long-term effects were evident on the scenic 

 qua I i ty of the area. 



In summary, scraping operations typically occurred in both active and 

 inactive floodplains. Both vegetated and unvegetated areas were used but 

 the fewest long-term disturbances occurred where only exposed gravel de- 

 posits were scraped. The potential for broadening or diverting channel flow 

 in split and single channel systems is great if depths of excavation are 

 excessive and locations of sites are poor. The potential for braiding in 

 these situations was increased with concomitant changes in aquatic biota. 

 Terrestrial effects were greatest when the depth of excavation was excessive 

 and led to permanent ponding which retarded recovery to predi sturbance 



562 



