关键词：
Dams
Bedload
Passive tracer
RFID
Connectivity
Virtual velocity
摘要：
Considerable research over the past several decades shows that dams, especially large, flow regulating structures, fragment watersheds and serve to disconnect the normative downstream flux of sediment and nutrients. Less attention has addressed smaller, channel-spanning Run-of-River (RoR) dams that are more commonly distributed throughout watersheds. Taking advantage of a suite of RoR dams in New England (USA), we quantify bedload flux into, through, and beyond the reservoir, and we calculate the residence time of gravel clasts. We used traditional channel surveys to evaluate (dis)equilibrium channel form and develop two equilibrium metrics based on bankfull shear stress and the bankfull Shields parameter. Additionally, we compartmentalize the bankfull channel Shields parameter as a linear combination of bedload and suspended load components to better quantify channel evolution in response to changes in sediment supply. To accomplish these goals, we embedded Radio Frequency Identification (RFID) PIT tags in 791 gravel clasts ranging in size from 15 mm to 81 mm, which were subsequently deployed within and upstream of the impounded reservoirs. Among the 503 tracers that were transported from their deployment location, the median cumulative distance traveled was 30 m and the maximum cumulative displacement during the study period was 758 m. Of the total tagged rocks placed at all five sites, 276 rocks were displaced over the dam, 204 of which spent time in the reservoir between high discharge events;the rest were transmitted through the reservoir and over the dam in a single high discharge event. Among those tracers that spent time in the reservoir prior to transmission over the dam, the average reservoir residence times at the different sites ranged from 19 to 203 days. The median grain sizes of tracers that were transported over the dam were identical to those that moved during the study period and similar to the median grain size of the channel bed. The distribution
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详细信息
中文科技期刊
