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Using Lagrangian Random Walk Particle Methods to Simulate Transport and Storage of Sediment and Associated Contaminants in Rivers: D. Nathan Bradley
Project Title:Using Lagrangian Random Walk Particle Methods to Simulate Transport and Storage of Sediment and Associated Contaminants in Rivers
Mendenhall Fellow: D. Nathan Bradley, (303) 278-7935,
Duty Station: Golden, CO
Start Date: October 1, 2010
Education:Ph.D Geomorphology, University of Colorado, 2010; B.A Astronomy, Northwestern University, 1995
Research Advisors: Jonathan Nelson, (303) 278-7957,; Ken Bencala, (650) 329-4409,; David Parkhurst, (303) 236-5098,; David Rubin, (831) 427-4736,
  Nate Bradley

Project Description: Erosional and depositional features in an alluvial stream are the result of a large number of individual sediment particle trajectories. Pools, riffles, bars, and islands are created and destroyed as sediment grains are eroded, transported and deposited. The location and stability of these features depend on both particle transport lengths and the storage time between episodes of motion. While these features may be small relative to the size of a river, they exert a first-order control on the flow of water, provide important habitat for fish, birds, and other wildlife, and may be both sinks and secondary sources of sediment-associated pollutants (especially in larger rivers).

The goal of this project is to develop a Lagrangian particle tracking model capable of routing fluvial sediment in multiple dimensions and at the fine scales necessary to reproduce relatively small erosional and depositional features. The model takes advantage of the statistical properties of random walks to infer broader transport patterns from the trajectories of a population of representative tracer particles moving in response to a simulated flow of water. The model will be tested against observations of the motion of ~900 rocks labeled with Passive Integrated Transponder (PIT) tags in an alpine stream in Colorado. This tracer experiment began in 2007 and is ongoing. The PIT tags equip each rock with a unique identifier that can be read from up to 1 m away. This technology enables us to recover a very high percentage (96% in 2010, 98% in 2009) of tracer particles each year and to identify the tracers without disturbing them. These data, combined with high-resolution topographic and discharge measurements, provide a unique opportunity to testing our sediment routing model.

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Last modified: 16:08:26 Thu 13 Dec 2012