Establishing an unambiguous connection between grain size and style of sediment transport in the Lower Niobrara River, Nebraska, USA

The transport of sediment is often separated into two components, bedload and suspended load. This division is important because bedload has a dominant control on channel morphology while suspended load dominates the formation of overbank deposits. Experimental data has related the style of sediment transport to mean flow conditions and bed topography. However direct application of this method in natural, sandy rivers is difficult due to large variabilities in flow. We propose a method for determining local flow conditions using the distribution of grain sizes traveling in the water column. Local shear velocity is found by fitting the Rouse equation for suspended sediment transport to measured sediment concentrations. Empirical criteria for distinguishing between suspended load and bedload are used to determine the fraction of sediment traveling in each respective mode. Application of this method to the Niobrara River, Nebraska, shows that -80 % of the sediment is traveling as suspended load, ~ 20 % is traveling in a transitional mode between bedload and suspended load and less than 1 % is traveling as pure bedload. We establish an unambiguous connection between grain size and the style of sediment transport and highlight the importance of the transitional transport mode in natural systems.

Department dc:contributor.department

Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2006

Author dc:creator

• Leung, Vivian

Advisor dc:contributor.advisor

• David Mohrig.

• Earth, Atmospheric, and Planetary Sciences.

Statement dc:rights

• MIT theses are protected by copyright. They may be viewed, downloaded, or printed from this source but further reproduction or distribution in any format is prohibited without written permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/114120

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/114120