TRACKING THE MORPHOLOGICAL CHANGES DURING A DRY VERSUS RAINY SEASON AT THE PAJARO RIVER ESTUARY USING UAS
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Authors
Helms, Joshua J.
Subjects
ephemeral river
unmanned systems
UAS
aerial photography
inlet migration
beach morphology
LiDAR
nearshore sediment transport
river discharge
Pajaro River
topography
wave height
unmanned systems
UAS
aerial photography
inlet migration
beach morphology
LiDAR
nearshore sediment transport
river discharge
Pajaro River
topography
wave height
Advisors
Orescanin, Mara S.
Date of Issue
2023-12
Date
Publisher
Monterey, CA; Naval Postgraduate School
Language
Abstract
Drastic morphological change occurs annually at the ephemeral river at Pajaro River beach as an inlet is created upon breaching to the Monterey Bay. This inlet breach, and subsequent migration of that inlet, affects the local community with increased flood events and ecological impacts with loss of access to the bay, and it can be hazardous for Amphibious and Naval Special Warfare (NSW) operations at similar beach sites. River discharge, river height, significant wave height, and wave radiation stress all contribute inlet breaching and subsequent migration. Once breached, the inlet at Pajaro migrates south before ultimately closing toward the end of the water year. Using unmanned aerial systems (UAS) with a LiDAR payload, UAS for videography and photography, GNSS walking surveys, and Sentinel L-2A satellite data, this study collected two water years of data (01OCT2021–30SEP2023) to compare a heavy precipitation water year (2023) to a normal, or dry, water year (2022), to better understand inlet breaching, closure, and migration rates. This study shows that during wetter winter months, inlet migration is dominated by high river discharge from the increased amount of rain water. Once the transition to summer occurs, the dominant factor in inlet migration is offshore waves. For a high precipitation water year, this study shows the inlet migration travels farther, the inlet stays open longer than the typical annual cycle, and fewer (zero for this case) closures will occur.
Type
Thesis
Description
Series/Report No
Department
Oceanography (OC)
Organization
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NPS Report Number
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Distribution Statement
Approved for public release. Distribution is unlimited.
Rights
This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.