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Groundwater Responses To Tidal Restoration At Pelican Marsh And Sea-Level Rise In Elkhorn Slough, California, Julie E. Nelson

Graduate Theses and Dissertations

Coastal wetlands represent a dynamic but vulnerable terrestrial-aquatic interface with future resilience controlled by historic hydrologic alterations, sea-level rise, and groundwater extraction. In diked coastal settings, poor tidal connectivity can degrade habitat from the impoundment of freshwater or hypersaline surface waters. Restoring tidal connectivity could foster marsh revitalization, but altering the surface hydrologic system could lead to unwanted salinity intrusion in shallow aquifers. Saline groundwater intrusion degrades freshwater quality and, while inevitable with sea-level rise, could be accelerated with tidal marsh restoration. To investigate this, I developed a steady-state groundwater flow model of Pelican Marsh, a diked, muted tidal marsh …

Low Methane Emissions From Nutrient-Rich Former River Channels In A Hydrologically Managed Dryland Delta, Siena Stassi, Jude A. Benavides, Chu-Lin Cheng, Marcelo Gomes Da Silva, Nicholas E. Ray, Nathan O. Barros, Rafael M. Almeida

School of Earth, Environmental, & Marine Sciences Faculty Publications

Anthropogenic stresses in dryland regions can alter hydrology, salinization, and biogeochemical processes. How these pressures influence methane (CH4) cycling and emissions from aquatic ecosystems remains poorly understood. Over the course of 1 year, we measured diffusive and ebullitive CH4 emissions from resacas—shallow, hydrologically managed distributary channels prevalent throughout the Lower Rio Grande Valley along the US–Mexico border. Despite warm, nutrient-rich waters, CH4 emissions from resacas were low, and more comparable to rates observed in estuarine systems. CH4 fluxes were positively related to temperature but negatively related to salinity and rainfall. Elevated salinity, driven by evaporation and source water from the …

Ecological Insights And Management Implications Of The Global Migratory Connectivity Of Green Turtles, Jaime Restrepo, Dina Nisthar, Harris Wei-Khang Heng, Lily K. Bentley, Corrie Curtice, Sarah Deland, Ei Fujioka, Patrick N. Halpin, Sarah K. Poulin, Roldán A. Valverde

School of Earth, Environmental, & Marine Sciences Faculty Publications

Aim

Green turtles are a widely distributed and highly migratory species; despite extensive data on their movement, there is no species-specific global synthesis on the subject. Based on three decades of published literature and building on previous global analyses, we developed a global network model of migratory connectivity for green turtles to better understand their spatial biology.

Location

Global.

Time Period

1990–2022.

Major Taxa Studied

Green Sea Turtle (Chelonia mydas).

Methods

We conducted a structured literature review extracting georeferenced information on the movement of green turtles from 1990 to 2022, aggregating this information into a single connectivity model, …

Machine-Learning Landslide Susceptibility And Runout Modeling In The Nolichucky River Gorge After Hurricane Helene, Grace Braver

Electronic Theses and Dissertations

Extreme rainfall from Hurricane Helene (September 2024) triggered widespread landslides across the southern Appalachian region, highlighting the need for rapid landslide susceptibility assessments that capture both landslide initiation and downstream runout. Traditional susceptibility models often focus solely on initiation zones, limiting their ability to identify which slopes will generate destructive landslides or where material will travel. This study addresses that gap by (1) integrating Geographic Information System (GIS)-based machine learning susceptibility modeling using ArcGIS Pro: Maximum Entropy (MaxEnt) and Random Forest-Based and Boosted Classification and Regression (FBBC) and (2) the U.S. Geological Survey (USGS) Grfin (Growth, Flow, and Inundation) runout …

Integrated Geophysical, Geotechnical, And Mineralogical Characterization Of Expansive Weches Formation Soils In East Texas: Implications For Infrastructure Design, Samuel Annobil

Electronic Theses and Dissertations

This study investigates the geotechnical, geophysical, and mineralogical characteristics of soils derived from the Weches Formation in Nacogdoches County, East Texas, with emphasis on the relationships among electrical resistivity, moisture condition, compaction state, and mineralogical composition. The Weches Formation is well known for producing clay-rich, moisture-sensitive soils that pose challenges to subgrade performance because of their plasticity and swelling behavior. Representative soil samples were collected and subjected to laboratory testing, including particle size analysis, Atterberg limits, Standard Proctor compaction, free swell tests, electrical resistivity measurements, and X-ray diffraction (XRD) mineralogical analysis. The soils are predominantly fine-grained and clay-rich, with USCS …

Sequential Products Of Anaerobic Denitrification In Calcareous And Noncalcareous Soils By Use Of The Gas Chromatograph, Grant S. Cooper

All Graduate Theses and Dissertations, Fall 2023 to Present

The sequential products of anaerobic denitrification were determined on seven Western soils (four alkaline, two acid, and one neutral) by soil and gas analysis. The soils with 1% alfalfa and added KNO3 were incubated at moistures slightly greater than field capacity and with an atmosphere of He. The soils and gases were periodically analyzed and balance sheets prepared. The sequence of NO3-->NO2-->N2O-->N2 operated in all soils. The rates of nitrogen interchanges and maximal amounts of nitrate, N2O2 and N2 were determined. From this data it was postulated that the rate-limiting process for denitrification in acid soils is …

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