| MITIGATION OF SEDIMENTATION HAZARDS DOWNSTREAM FROM RESERVOIRS |
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| 作者姓名： | Ellen WOHL Sara RATHBURN |
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| 作者单位： | Department of Earth Resources，Colorado State University Ft. Collins，CO，USA |
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| 摘 要： | 1 INTRODUCTION Increasing attention is being given to sedimentation hazards downstream from reservoirs as dams built during the past century accumulate progressively greater volumes of sediment. The sediment storage both decreases reservoir capacity and operating efficiency of the dam, and creates a 搒ediment-shadow?downstream where sediment-starved flows commonly erode channel boundaries and create long-term channel instabilities. Numerous studies have documented downstream channel change…
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MITIGATION OF SEDIMENTATION HAZARDS DOWNSTREAM FROM RESERVOIRS |
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| Ellen WOHL
,Sara RATHBURN.MITIGATION OF SEDIMENTATION HAZARDS DOWNSTREAM FROM RESERVOIRS[J].International Journal of Sediment Research,2003,18(2). |
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| Authors: | Ellen WOHL Sara RATHBURN |
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| Abstract: | Many reservoirs currently in operation trap most or all of the sediment entering the reservoir,creating sediment-depleted conditions downstream. This may cause channel adjustment in the form of bank erosion, bed erosion, substrate coarsening, and channel planform change. Channel adjustment may also result from episodic sediment releases during reservoir operation, or from sediment evacuation following dam removal. Channel adjustment to increased sediment influx depends on the magnitude, frequency, duration and grain-size distribution of the sediment releases, and on the downstream channel characteristics. Channel adjustment may occur as a change in substrate sizedistribution, filling of pools, general bed aggradation, lateral instability, change in channel planform,and/or floodplain aggradation. The increased sediment availability may alter aquatic and riparian habitat, reduce water quality, distribute adsorbed contaminants along the river corridor, and provide germination sites for exotic vegetation. Mitigation of these sedimentation hazards requires: (1)mapping grain-size distribution within the reservoir and estimating the grain-size distributions of sediment that will be mobilized through time; (2) mapping shear stress and sediment transport capacity as a function of discharge on the basis of channel units for the length of the river likely to be affected; (3) mapping potential depositional zones, and aquatic habitat and "acceptable losses," along the downstream channel, and comparing these volumes to the total sediment volume stored in the reservoir as a means of estimating total transport capacity required to mobilize reservoir sediment delivered to the channel; (4) designing discharge and sediment release regime (magnitude, frequency,duration) to minimize adverse downstream impacts; and (5) developing plans to remove, treat, contain,or track contaminants, and to restrict establishment of exotic vegetation. The North Fork Poudre River in Colorado is used to illustrate this approach to mitigating sediment hazards downstream from reservoirs. |
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| Keywords: | Reservoir sediment Hazards Downstream channel adjustments |
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