Sediment Flux Through The Rio Grande River

Author : Changxing Shi
Publisher : Open Dissertation Press
ISBN 13 : 9781374724495
Total Pages : pages
Book Rating : 4.7/5 (244 download)

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Download or read book Sediment Flux Through the Yellow River Sediment Routing System written by Changxing Shi and published by Open Dissertation Press. This book was released on 2017-01-27 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "Sediment Flux Through the Yellow River Sediment Routing System" by Changxing, Shi, 師長興, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled 'Sediment Flux through the Yellow River Sediment Routing System' Submitted by SHI Changxing for the degree of Doctor of Philosophy at The University of Hong Kong in August 2002 Sediment fluxes through riverine sediment routing systems are one of the main causes for many environmental problems and disasters, to which the effective solutions should be based on quantification of the sediment fluxes and clarification of related mechanisms. This study probed into the sediment fluxes through one of the largest riverine sediment routing systems in the world, the Yellow River sediment routing system, in a spatial detail of four basic functional cells and on time scales of 0 4 10 -10 years. Investigation of the sediment fluxes was carried out through construction of sediment budgets of the system mainly based on information derived from deposits in the sinks and records of sediment load, and through analyzing some important mechanisms for the characteristics of the constructed sediment fluxes in the system. The dry bulk densities of deposits in various depositional environments in the system were investigated for acquiring reliable sediment budgets from deposits. The sediment budget for about 10 years when the Diaokouhe lobe of the Yellow River delta was formed was 14.510 tones of sediment income distributed into the lower Yellow River, the delta, and the sea by proportions of 33%, 49%, and 18%, respectively. The high proportion of sediment deposition in the delta was associated with the high sediment-sequestering efficiency of the ephemeral sediment-charged hyperpycnal underflows off the river mouth and floods over the delta plain because these two processes tend to arrest all the incoming fine as well as coarse particles. A positive relation exists between the proportion of sediment deposited in the deltaic lobe and sediment discharge. The amount of sediment escaping from the delta displays an exponentially decreasing trend with the distance from the delta front. 11 The sediment budget for the period from 1855 to 1968 was 1.87810 tons of sediment income deposited in the lower reaches and the river delta by proportions of 62% and 32%, respectively. The larger proportion of sediment deposition in the lower reaches was associated with the nonexistence of dykes during the period from 1855 to 1875 and the frequent dyke breaching before 1949. It was found that the percentages of sediment deposition in the delta on two time scales are different because the expanding delta captures the sediments, which were deposited in front of the delta in the earlier periods. The total sediment yield from the source in the Holocene was found to be about 12 810 tons, which was the total mass of sediments accumulated in all the sinks of the system. Using radiocarbon dates in the Huang-Huai-Hai Plain, it was revealed 9 that the annual sediment yield on a 2500-year average increased from 0.6810 tons 9 in the first quarter to 1.0110 tons in the last quarter of the Holocene. Furthermore, it was disclosed that human activities enlarged the sediment yield by a total of about 12 0.310 tons over the past 2500 years and were the cause for the difference between 9 the measured sediment yield of 1.610 t/yr and the predicted natural sediment yield 9 of 0.9510 t/yr in the middle of the last century. DOI: 10.5353/th_b2985194 Subjects: