UVM Theses and Dissertations
Format:
Print
Author:
Garvey, Kerrie M.
Dept./Program:
Natural Resources
Year:
2012
Degree:
MS
Abstract:
High sediment loads in rivers and streams are one of the most widespread and important causes of impairment nationally and worldwide. Negative impacts include decreased water quality, channel stability, and habitat health, as well as the economic costs to address these issues. Locally, state and provincial governments have attempted to limit non-point sources of sediment and closely linked phosphorus loading to Lake Champlain and other waters in recent decades. Quantitative estimates of the relative importance of sediment sources, and in particular agriculture vs. streambank erosion, is needed at watershed spatial scales to support these efforts.
This study takes advantage of recent advances in remote sensing to develop and demonstrate a robust and cost effective methodology to estimate the relative contribution of streambank erosion associated with fluvial planform change over time at site, reach, and watershed spatial scales. Our analyses focused on 11 watersheds in Chittenden County, VT over a three year study period (2004-2007). In our first analysis, multi-date LiDAR-derived elevation data and high spatial resolution digital orthophotography were employed to estimate total erosion (51,575 mT) and total deposition (42,664 mT) along a 23 km section of the Browns River. Total erosion was then partitioned to estimate streambank erosion (34,290 mT) and channel erosion (17,285 mT). Because the availability of multi-date LiDAR is limited, however, our second analysis addressed streambank erosion only, using multi-date orthophotography and single-date LiDAR data.
Our results confirm not only the overall importance of streambank erosion to sediment loading to adjacent waters, but also the wide variability in its relative contribution at reach and watershed spatial scales. Estimates of total sediment loading attributable to streambank erosion ranged from 15 to 80% on a reach by reach basis. First order estimates of watershed-scale sediment loading ranged from 398 to 6,505 mT over the study period, comparing well to previous field studies. Our remote sensing approach not only identifies specific sites, reaches, and watersheds that are disproportionately contributing sediment and nutrients to receiving waters, but also offers watershed and corridor management efforts the potential to prioritize resources and evaluate management strategies at watershed scales.
This study takes advantage of recent advances in remote sensing to develop and demonstrate a robust and cost effective methodology to estimate the relative contribution of streambank erosion associated with fluvial planform change over time at site, reach, and watershed spatial scales. Our analyses focused on 11 watersheds in Chittenden County, VT over a three year study period (2004-2007). In our first analysis, multi-date LiDAR-derived elevation data and high spatial resolution digital orthophotography were employed to estimate total erosion (51,575 mT) and total deposition (42,664 mT) along a 23 km section of the Browns River. Total erosion was then partitioned to estimate streambank erosion (34,290 mT) and channel erosion (17,285 mT). Because the availability of multi-date LiDAR is limited, however, our second analysis addressed streambank erosion only, using multi-date orthophotography and single-date LiDAR data.
Our results confirm not only the overall importance of streambank erosion to sediment loading to adjacent waters, but also the wide variability in its relative contribution at reach and watershed spatial scales. Estimates of total sediment loading attributable to streambank erosion ranged from 15 to 80% on a reach by reach basis. First order estimates of watershed-scale sediment loading ranged from 398 to 6,505 mT over the study period, comparing well to previous field studies. Our remote sensing approach not only identifies specific sites, reaches, and watersheds that are disproportionately contributing sediment and nutrients to receiving waters, but also offers watershed and corridor management efforts the potential to prioritize resources and evaluate management strategies at watershed scales.