Date of Award

1-1-2011

Document Type

Campus Access Dissertation

Department

Geography

First Advisor

L. Allan James

Abstract

Advances in remote sensing technologies can facilitate acquisition of topographical and planimetric information in fluvial environments and can produce spatial data with high spatial and temporal resolutions. Measuring planimetric and volumetric change in fluvial sediment budgets and geomorphic change detection was used for long-term monitoring of a fluvial system. Channel and floodplain changes caused by hydraulic gold mining sediment in this system are a major example of anthropogenic impacts on a fluvial system.

This study uses remote sensing change-detection techniques to examine spatial and temporal patterns of HMS redistribution at a centennial time scale, and to measure and evaluate the magnitude and processes of a major channel and floodplain metamorphosis. Five reach-scale sites along the lower Yuba River and two sites on the Feather River were chosen for detailed analysis of planimetric and volumetric changes over a period of ~100 years. Volumetric changes were measured using DEM differencing and soft-copy photogrammetry methods, and planimetric changes were recorded from rectified maps and aerial photographs.

This study indicates significant changes in channel morphology and sediment storage over the last 100 years. Large deposits of historical sediment remaining in the bed, banks and terraces of the lower Yuba River were remobilized by floods. The volumetric analysis shows the results of dredging of ditches, deposition in natural levees, and net erosion of high-water channels from 1906 or 1909 to 1999. Over the last century, channels incised up to ~13 m into mining sediment deposits. Systematic uncertainty analysis reveals vertical errors are mostly dependent on the topographical slopes and maximum errors are concentrated on the steep channel banks and scarps. The planimetric analysis shows significant reworking of sediment occurred throughout the 72-year period from 1937 to 2009. Substantial amounts of HMS remobilization occurred during major flood events and contributed substantial amounts of sediment downstream, but erosion was not significantly greater than deposition. The rates of channel change and areal extent of sediment reworking by floods decreased towards the later part of the century even though flood magnitudes did not decrease.

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