Date of Award

4-2022

Degree Name

Master of Science

Department

Geography

First Advisor

Adam J. Mathews, Ph.D.

Second Advisor

Lisa M. DeChano-Cook, Ph.D.

Third Advisor

Chansheng He, Ph.D.

Keywords

Geomorphology, Lake Michigan, remote sensing, seawall, UAS, UAV

Access Setting

Masters Thesis-Open Access

Abstract

The high-water level of Lake Michigan (LM) in the past few years has led to significant periods of erosion and increased the risk to private property owners on the coast. To cope with this, many property owners on the coast of LM have constructed coastal protections, some opting for seawalls. Previous studies have assessed the effects of seawalls but disagreed on their impacts, and only laboratory studies were able to establish their range of influence. Using a different method to study their effects will be pertinent to understanding them.

This research aims to use a higher temporal and spatial resolution approach, Unoccupied Aircraft System (UAS) aerial image collection with Structure from Motion (SfM) image processing, than previous studies to examine the effects of a seawall on an adjacent Lake Michigan beach. Previous studies have relied on satellite imagery or visual observation to conclude results. However, satellite data does not provide 3-dimensional data and are too low a resolution for repeat observation, and visual inspection can introduce bias.

Over 9 months and 18 aerial surveys of a public park on Lake Michigan, 2D and 3D changes in the beach and dune were recorded. Using the extent of shorelines, two sites were set up: site 1 under influence of the seawall and site 2, under no influence. Measurements were made between shoreline positions to create the shoreline average difference variable. A t-test of unequal variances was used to determine if site 1 had more erosion than site 2 (p < .50). For 3D data, elevation change values were gathered using raster differencing. There were significant negative elevation changes in many parts of the dune (<-2.5 ft). However, due to issues with the SfM-MVS method, the dune covered in heavy vegetation, elevation changes could not be obtained. Thus, it is difficult to discern if the changes are brought on the adjacent seawall or if other factors such as tourist movement or heavy storms could have caused the negative elevation changes.

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