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dc.contributor.advisorKelin X. Whipple.en_US
dc.contributor.authorJohnson, Joel Petersonen_US
dc.contributor.otherMassachusetts Institute of Technology. Dept. of Earth, Atmospheric, and Planetary Sciences.en_US
dc.date.accessioned2008-09-03T15:10:09Z
dc.date.available2008-09-03T15:10:09Z
dc.date.copyright2007en_US
dc.date.issued2007en_US
dc.identifier.urihttp://hdl.handle.net/1721.1/42277
dc.descriptionThesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2007.en_US
dc.descriptionIncludes bibliographical references.en_US
dc.description.abstractThis thesis explores the dependence of bedrock channel incision on coarse sediment supply through laboratory flume experiments and quantitative field observations of evolving channel morphology. Predictions of the saltation-abrasion model (Sklar and Dietrich, 2004) for sediment flux-dependent channel incision guide our efforts although the results are not model dependent. In channels where the dominant incision process is sediment abrasion, sediment transport and erosion are inherently coupled. Flume experiments support the form of sediment flux-dependent relations proposed in the saltation-abrasion model, but also suggest that the model is incomplete: channel bed morphology adjusts due to localized erosion, and bed morphology in turn influences local flow and sediment transport. The experiments document a positive feedback in which bedload is preferentially transported in local topographic lows due to lateral transport and abrasion in turn deepens those topographic lows. Under sediment-starved conditions this positive feedback results in the incision of narrow inner channels. In the Henry Mountains of southeast Utah, we monitored channel flow and resulting bedrock incision over 2.5 years in a human-perturbed bedrock channel where erosion had incised a narrow inner channel in which sediment transport and erosion were focused, similar to the flume experiments. In addition, the flow record shows that the maximum discharge flood was much less erosive than a lower but prolonged flood due to snowmelt flow. Large flash floods can be net depositors of coarse sediment in the channel, mantling the channel bed with coarse sediment and inhibiting erosion.en_US
dc.description.abstract(cont.) Finally, a quantitative comparison of tributaries in a Henry Mountains river network shows that channels with higher coarse sediment loads maintain steeper channel slopes and are less incised than smaller drainage area tributaries with less coarse sediment but more exposed bedrock. These field observations validate the idea that sediment cover can inhibit channel incision into bedrock, and also suggest that the slope of incising bedrock channels can adjust to transport the sediment load of the channel rather than to incise bedrock. We found in the flume experiments that erosion adjusts the morphology of bedrock channels until a state is reached where channel flow just transports the imposed sediment load, suggesting that the equilibrium state of bedrock channels is a transport-limited condition. Together, the chapters demonstrate how incising channels respond to changes in coarse sediment load, emphasizing the effects of sediment cover in inhibiting incision and morphological adjustments of channel bed topography.en_US
dc.description.statementofresponsibilityby Joel Peterson Johnson.en_US
dc.format.extent223 p.en_US
dc.language.isoengen_US
dc.publisherMassachusetts Institute of Technologyen_US
dc.rightsM.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.en_US
dc.rights.urihttp://dspace.mit.edu/handle/1721.1/7582en_US
dc.subjectEarth, Atmospheric, and Planetary Sciences.en_US
dc.titleFeedback between erosional morphology, sediment transport and abrasion in the transient adjustment of fluvial bedrock channelsen_US
dc.typeThesisen_US
dc.description.degreePh.D.en_US
dc.contributor.departmentMassachusetts Institute of Technology. Dept. of Earth, Atmospheric, and Planetary Sciences.en_US
dc.contributor.departmentMassachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences
dc.identifier.oclc231847212en_US


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