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ARS Home » Southeast Area » Oxford, Mississippi » National Sedimentation Laboratory » Watershed Physical Processes Research » Research » Publications at this Location » Publication #336429
Title: Laboratory calibration of impact plates for measuring gravel bed load size and mass

Author
item Kuhnle, Roger
item Wren, Daniel
item HILLDALE, ROBERT - Us Bureau Of Reclamation
item GOODWILLER, BRADLEY - University Of Mississippi
item CARPENTER, WAYNE - University Of Mississippi

Submitted to: Journal of Hydraulic Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/22/2017
Publication Date: 12/1/2017
Citation: Kuhnle, R.A., Wren, D.G., Hilldale, R.C., Goodwiller, B.T., Carpenter, W.O. 2017. Laboratory calibration of impact plates for measuring gravel bed load size and mass. Journal of Hydraulic Engineering. 143(12), 06017023 doi:10.1061/(ASCE)HY.1943-7900.0001391.

Interpretive Summary: Knowledge of the rate of gravel movement in streams in which a dam has recently been removed is important for a number of reasons. Much sediment including gravel is generally impounded in the reservoirs behind dams. The rate of movement and the fate of this sediment after dam removal is critical for assuring that channel instability does not occur downstream of the removed dam. Channel instability may cause bank erosion, flooding, and be detrimental to fish and other aquatic biota living in the channel. A series of impact plates were installed in the Elwha River to monitor the transport of gravel following the removal of two dams on the river in 2012 and 2014. Experiments were conducted in a laboratory flume at the National Sedimentation Laboratory to calibrate replica impact plates of the ones installed in the Elwha River. The plates were successfully calibrated using data from a series of experiments conducted in a laboratory flume. The mass and size of gravel sediment greater than 5.7 mm which passes over the plates were calculated accurately using the calibration equations. Methods to adapt the calibrations to the Elwha River are being developed. Calibration relations for the impact plates on the Elwha River will allow river managers to adaptively manage the removal of the impounded sediment in a more informed and environmentally sensitive manner.

Technical Abstract: Continuous monitoring of gravel transport in rivers is necessary for understanding the impact of dam removal on river systems. Impact plates, such as those deployed on the Elwha River in the state of Washington, USA, are a promising technique; however, relating the data generated by the plates to sediment load is difficult. In order to refine methods described in a recent study, coarse bed load transport was measured and compared to the output from two accelerometer equipped impact plates which were full scale replicas of 72 plates deployed in the Elwha River. Relations were developed for converting the signal amplitude generated by particles impacting the plates to mass. Mean discrepancy ratios indicated that estimates of coarse bed load transport were within 25% of the measured if one outlier from the experiments was removed. Methods to transfer these relations to field locations are also discussed.