Dissertation/Thesis Abstract

Quantifying geomorphic change to a point bar in response to high flow events using terrestrial lidar, White Clay Creek, DE
by Orefice, Michael J., M.S., University of Delaware, 2015, 78; 1602341
Abstract (Summary)

Light Detection And Ranging (LiDAR) data can be used to accurately model three- dimensional surfaces for quantifying fluvial erosion and deposition. Terrestrial LiDAR is typically used for monitoring banks, but can be used for monitoring planar forms such as point bars. Point bars are topographic features that form on the convex bank of a meander. While point bars are considered to be formed by depositional processes, they display features such as chute channels and scour holes that suggest that erosion, due to high flow events, may significantly influence point bar evolution. Through the use of Terrestrial Laser Scanning (TLS), we observed how a point bar on the White Clay Creek near Newark, Delaware, responded to a flood event with a return period of 6.1 years, and to multiple small events over a 1 year period with return periods between 1.00 and 1.25 years. Scans of the point bar were completed on April 11, 2014, May 8, 2014, and April 16, 2015. Scans were referenced to a common coordinate system, scan data representing vegetation points were removed, and three 0.1 m x 0.1 m gridded Digital Elevation Models (DEMs) were created from the remaining data. DEMs of Difference (DoDs) were calculated by subtracting the cell values in subsequent DEMs and by thresholding out positional and surface roughness errors. The 6.1 year flood that occurred between the April 11, 2014 scan and the May 8, 2014 scan resulted in 88.53 m3 of erosion and 39.12 m3 of deposition. The net volumetric change was -49.40 m3 over an area of 631.72 m2. The smaller events that occurred between the May 8, 2014 scan and the April 16, 2015 scan resulted in 13.33 m3 of erosion and 53.46 m 3 of deposition. The net volumetric change was x i 40.13 m 3 over an area of 620.74 m2. Our results suggest that 1) sediment deposited on point bars is eroded frequently by flood events; and 2) TLS can provide useful estimates of erosion and deposition. Although our results are for a short period, longer datasets can be used to calculate sediment residence times for point bar deposits. Additionally, we can gain a better understanding of how point bar deposits are preserved in the geologic record. This information is useful for creating accurate sediment budgets, remediating contamination issues, and interpreting geologic history.

Indexing (document details)
Advisor: Pizzuto, James E.
Commitee: Mitchell, Jessica J., O'Neal, Michael A.
School: University of Delaware
Department: Geology
School Location: United States -- Delaware
Source: MAI 55/02M(E), Masters Abstracts International
Subjects: Geographic information science, Geology, Geomorphology
Keywords: Fluvial geomorphology, Gis, Lidar, Point bar
Publication Number: 1602341
ISBN: 978-1-339-16363-5
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