Under what conditions do parallel channel networks occur?

Jung, Kichul, author
Niemann, Jeffrey D., advisor
Huang, Xiangjiang, committee member
Wohl, Ellen E., committee member
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Geologists have long recognized that channel networks can deviate from a typical dendritic form when they develop under certain geologic or topographic constraints. One such deviation is the so-called parallel form, which is thought to develop when the pre-existing surface is sloping. The objectives of this research are to determine the specific conditions under which parallel networks occur and the nature of the transition between dendritic and parallel networks. Both real and simulated channel networks are analyzed in this study. The real networks were obtained from the digital elevation models of basins that include large areas of the pre-existing topographic surface. Such areas were identified as locations with small drainage areas and topographic curvatures that are close to zero. For each basin, the average slope of the pre-existing surface was calculated by averaging the local slopes for all points that are part of the pre-existing surface. Each channel network was then classified using a recently published method that can distinguish five different network types (including dendritic and parallel) based on three measures that are derived from scaling-invariance. These measures focus on the increments of drainage area along a channel, the irregularity of channel courses, and 111 the angles formed by merging tributaries. Based on these classifications, it is observed that natural networks become abruptly parallel when the average slope of the pre-existing surface exceeds about 3%. Simulated channel networks were also generated using a detachment-limited model for fluvial erosion and a slope-dependent model for hillslope processes. The parameters of the model were determined to imitate the real basins, and the average slope of the pre-existing surface was used for the slope of the initial surface. Based on these simulations, the model can also produce a transition between dendritic and parallel networks for an initial slope around 3%, but this threshold depends on the roughness of the initial surface and the boundary conditions.
2010 Fall.
Includes bibliographic references (pages 53-57).
Covers not scanned.
Print version deaccessioned 2022.
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Fluvial geomorphology
River channels
River engineering
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