closed site will facilitate re-estab I i stiment of pre-mining vegetation con- 

 di t ions. 



If material sites are located and operated to prevent or greatly mini- 

 mize effects on channel hydraulics, and to utilize only exposed gravel 

 bars, the probability of major localized changes to a floodplain generally 

 is greatly reduced. Where exposed gravel bars are not available or are 

 inadequate, a tradeoff decision between sites must be made that weighs the 

 potential effects of aquatic disturbances against terrestrial disturbances. 

 In these cases, minimization of hydraulic change to active channels should 

 be important in the decision — major hydraulic changes can have a greater 

 long-term effect on terrestrial systems than the controlled disturbances 

 associated with a site located in a vegetated inactive floodplain or ter- 

 race. 



RECOMMENDED FUTURE STUDIES 



During the present study a number of subject areas were identified 

 that should be investigated. 



1. Evaluation of gravel mining from coastal and upland sources; and, 

 preparation of guidelines for users of these sources. These alternatives to 

 sources have not been studied. 



2. Evaluation of the effects of multiple sites on one river system. 

 Such an investigation should be aimed at determining the critical, spatial, 

 and temporal relationships of multiple sites. Gravel replenishment rate 

 predictions should be an integral part of this investigation. 



3. Several floodplain gravel removal sites should be investigated 

 before, during, and after mining to assess the adequacy of the Guidelines 

 Manua I . 



4. Several topics of the Guidelines Manual should be studied in detail 

 to assess their adequacy, (i.e., buffers, pit design, and active channel 

 dredging) . 



VI 



