Development of a Continuous Bedload Transport Measurement Technique

Project ID: 6499
Principal Investigator: Robert Hilldale
Research Topic: Sediment Management and River Restoration
Funded Fiscal Years: 2008 and 2009
Keywords: None

This is one of two types of sensors attached to the underside of the steel impact plates.<br>[<a href='imagepop.cfm?id=6499|170' target='_blank' style='color:#bbb'>view information</a>] This is one of the two types of sensors mounted to the stainless steel impact plates to measure vibration as gravel crosses the plate.  This accelerometer is multi-frequency and waterproof.<br>[<a href='imagepop.cfm?id=6499|172' target='_blank' style='color:#bbb'>view information</a>] These channels form the housing to which the instrumented plates are attached.  Wires from each sensor are also routed to the bank through these channels, which will span the channel end to end.<br>[<a href='imagepop.cfm?id=6499|174' target='_blank' style='color:#bbb'>view information</a>] Photograph of the channel with an impact plate mounted to it.  Note the conduit for routing wires and threaded backer bar for bolting the plates to the channel.<br>[<a href='imagepop.cfm?id=6499|176' target='_blank' style='color:#bbb'>view information</a>] Bed load impact sensors being installed across the Elwha River in 2009.<br>[<a href='imagepop.cfm?id=6499|178' target='_blank' style='color:#bbb'>view information</a>] Installation of the bed load impact sensors in 2009.<br>[<a href='imagepop.cfm?id=6499|180' target='_blank' style='color:#bbb'>view information</a>] Bed load impact plate installation in 2008.  Note the rubber strips used for acoustic isolation, which prevents strikes on one plate registering on the adjacent plate.  These plates are being installed in the low flow notch of the weir when the river flow was diverted and the channel was dry.<br>[<a href='imagepop.cfm?id=6499|182' target='_blank' style='color:#bbb'>view information</a>]

Research Question

There is a need to measure bedload downstream of two dams on the Elwha River (Glines Canyon and Elwha) in Washington that are slated for removal. The two major questions related to the proposed bedload measurement are:

* How well did Reclamation models predict the downstream transport of sediment accumulated in the reservoirs?

* At what rate is bedload being transported by the river channel below the two dams over time?

Reclamation will need to track the bedload released from the reservoirs over time so that modifications to the rate of dam removal can be made if necessary. The Elwha and Glines Canyon Dams are scheduled to be removed over a two to three year period.

Need and Benefit

Currently there is no method available for continuous monitoring of bedload on the Elwha River. Moreover, only a few continuous bedload monitoring methods or devices are currently being used around the world. By installing a series of bedload impact sensors (instrumented steel plates) across the channel, bedload can be measured at a specific location as it passes a fixed cross section. These steel plates will be attached to the downstream edge of a sheetpile wall that is being installed for water diversion purposes.

The method of bedload measurement currently available is direct sampling. This method requires a team of individuals to be present during sampling and is very costly. The sampler is usually deployed from a bridge, boat, or cableway and remains on the bed for several seconds to a few minutes, depending on the transport rate. Data collected in this fashion can only be applied to the conditions under which it was sampled, primarily discharge. During dam removal, bedload transport can not be assumed constant for a given discharge due to the temporal changes in sediment supply as the dams are being removed. Therefore, the bedload released from the reservoirs will not be able to be calculated using standard transport curves and direct sampling methods.

The benefit to Reclamation will be a surrogate bedload measurement method that will be calibrated in the lab and in the field. It is expected that the method will be proven reliable and could be applied elsewhere. This research may contribute to efforts by the Federal Interagency Sedimentation Project (FISP) to provide Federal approval for surrogate sediment measurement methods and devices. A tremendous need exists for continuously monitored bedload data, as current understanding of bedload transport is incomplete. Increased understanding of bedload transport will improve our predictive capabilities of sediment transport.

Contributing Partners

Contact the Principal Investigator for information about partners.

Research Products

Bureau of Reclamation Review

The following documents were reviewed by experts in fields relating to this project's study and findings. The results were determined to be achieved using valid means.

Acoustic Hydrophones to Measure Sediment Transport (final, PDF, 365KB)
By Robert C. Hilldale
Publication completed on September 30, 2009

This bulletin summarizes the research results and potential application to Reclamation's mission.

Not Reviewed

The following documents were not reviewed. Statements made in these documents are those of the authors. The findings have not been verified.

Development of a Continuous Bed Load Transport Technique (final, PDF, 8KB)
By Robert Hilldale
Report completed on June 10, 2011

There is a need to develop the ability to continuously measure bed load transport in rivers. To date, our ability to measure this quantity is very limited and has hindered complete understanding of the transport of gravel and cobble fractions of bed material. We are developing a system whereby continuous measurement of coarse bed material (> 10mm) will be accomplished with a series of 72 instrumented steel plates installed across the Elwha River in WA.

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Last Updated: 6/22/20