Geologic Publications for Mount Rainier

Simulating downstream impacts from synthetic sediment pulses in the Nisqually River, WA using a lagrangian, bed-material sediment transport model

[ back to previous page ]

Author(s): Muneer Ahammad, Jonathan A. Czuba, Allison M. Pfeiffer, Brendan P. Murphy, Patrick Belmont

Category: PRESENTATION
Document Type: Presentation #EP33E-2382
Publisher: American Geophysical Union Fall Meeting, San Francisco, CA
Published Year: 2019
Volume:
Number:
Pages:
DOI Identifier:
ISBN Identifier:
Keywords:

Abstract:
Sediment pulses delivered to a river can affect channel morphology, habitat conditions, and channel-floodplain connectivity in downstream reaches of the river network. The movement of sediment depends on the flow, grain size distribution, interactions among grain sizes, bed morphology, as well as the geometry of the channel and the network. Predicting the downstream evolution of sediment pulses enables identification of potential hotspots of aggradation and changes in channel characteristics. This study serves as essential validation for a model of the space-time evolution of sediment pulses and the physical disturbances to downstream reaches of a channel network. The model builds on a previous Lagrangian, bed-material sediment transport model, which is applied to a 27-kilometer reach of the mainstem Nisqually River (WA) draining Mt. Rainier and terminating in Alder Lake. We limit the simulation of transport to the mainstem of the river network in order to validate the Lagrangian framework against an existing one-dimensional river-hydraulic and sediment-transport model (The Unified Gravel-Sand (TUGS) model) and detailed field observations. In the Lagrangian model, episodic, discrete pulses of sediment are supplied at the most upstream end of the model, and we investigate the magnitude, timing, and persistence of downstream changes in bed elevation and grain size distributions. We utilize measured flow (66 year hydrograph) and grain size as inputs, and measurements of bed-elevation change (at a USGS gage) and sediment accumulation rates in Alder Lake to validate the model. Key modeling advancements include the consideration of stress partitioning and allowance for different upstream sediment supply conditions, such as transporting at capacity or applying a sediment rating curve. This study is important because it allows us to better characterize and understand the fluvial geomorphic response of different river reaches to variations in sediment supply.

View Report:
Sorry, no PDF is available - Contact Scott to get a copy

Suggested Citations:
In Text Citation:
Ahammad and others (2019) or (Ahammad et al., 2019)

References Citation:
Ahammad, M., J.A. Czuba, A.M. Pfeiffer, B.P. Murphy, and P. Belmont, 2019, Simulating downstream impacts from synthetic sediment pulses in the Nisqually River, WA using a lagrangian, bed-material sediment transport model: Presentation #EP33E-2382, American Geophysical Union Fall Meeting, San Francisco, CA,