Geosciences
http://hdl.handle.net/10211.3/141094
2024-03-29T08:21:34ZPressure-temperature conditions of kyanite-bearing migmatites at Ledge Mountain, central Adirondack Highlands
http://hdl.handle.net/10211.3/214128
Pressure-temperature conditions of kyanite-bearing migmatites at Ledge Mountain, central Adirondack Highlands
Swanson, Brandon Alexander
Sillimanite-bearing migmatites exposed at Ledge Mountain in the central Adirondack
Highlands are the only known location in the Highlands where kyanite has been found.
Phase equilibria modeling combined with geochemical and textural analysis suggests that
migmatites at Ledge Mountain experienced peak P-T conditions at 12-16 kbar/900-1040°
C followed by isothermal decompression into the sillimanite stability field, resulting in a
clockwise P-T path. At these conditions, pseudosection models predict that the rock in the
low-middle crust would have been -15-30% melt prior to exhumation. Presence of
peritectic garnet with lobate quartz inclusions, pseudomorphed melt films, and biotitequartz
symplectites indicates that garnet grew in the presence of melt following the
dehydration melting of micas during prograde metamorphism. These results indicate that
previous estimates of the P-T conditions of granulites in the Adirondack Highlands likely
underestimate the peak metamorphic conditions in which they formed due to the
inconsistencies of conventional thermobarometry at high-temperature conditions. During
orogenic collapse, the low-middle crust would have been ~15-30% melt which is more
than enough to cause channel flow and suggest that the Highlands formed as a gneiss dome,
similar to what has been suggested in other orogens such as the Himalaya. These results
support the conceptual model of the Grenville orogeny as a large hot orogen (LHO).
2019-01-01T00:00:00ZGroundwater recharge sensitivity to low impact development design and future climate variability
http://hdl.handle.net/10211.3/214006
Groundwater recharge sensitivity to low impact development design and future climate variability
Rodriguez, Jessica
Groundwater sustainability is at the forefront of resource management. In light of
climate change and growing populations, meeting future water needs must be met with
planning and innovation. This is particularly challenging in cities where recharge is often
limited by impervious surfaces and runoff is contaminated by urban pollutants. Low impact
development (LID) is a design strategy that mimics the natural hydrologic cycle and is
usually implemented as an alternative to the traditional stormwater system. Examples of
LID best management practices (BMPs) include rain gardens, bioswales, infiltration
trenches, rooftop gardens, and permeable pavement. LID BMPs delay and decrease peak
runoff flows and improve water quality, and there is a growing number of studies
investigating LID’s effect on groundwater. Understanding potential recharge under LID
BMPs and identifying the design features influencing recharge can serve an important role
in the move toward groundwater sustainability and management. In this study, I used
HYDRUS-1D to model five LID BMPs (two rain gardens, two bioswales, one infiltration
trench) from 1948-2099 with observed historic climate data and 9 global climate models
(GCMs) at representative concentration pathways (RCP) of 4.5 and 8.5. Mean recharge
ranged from 1725-3458 mm/yr under the LID BMPs, with the highest recharge rates
occurring under the infiltration trench. Though simulated recharge from historic, 4.5 and
8.5 RCP showed no statistically significant changes in recharge over time, runoff is
predicted to increase significantly, indicating that current LID BMPs should be redesigned
to store increased inflow expected from climate change. Recharge efficiency during heavy
rainfall events such as El Nino can be improved by increasing the loading ratio of a BMP.
Results of a one-at a time (OAT) method sensitivity analysis showed that the hydraulic
conductivity of the soil underlying a LID BMP has the most influence on recharge and
suggested that location is critical for optimizing or minimizing recharge.
2019-01-01T00:00:00ZHow small bugs tie down big rocks : measuring and modeling the forces acting between nets spun by Caddisfly larvae (Hydropsychidae) and gravel particles at the onset of motion
http://hdl.handle.net/10211.3/213960
How small bugs tie down big rocks : measuring and modeling the forces acting between nets spun by Caddisfly larvae (Hydropsychidae) and gravel particles at the onset of motion
Mclaughlin, Molly Katherine
Many organisms, both plants and animals, influence geomorphic processes in rivers. Common
aquatic insects, net-spinning caddisfly larvae (Tricoptera: Hydrospyche), build silk nets that can
increase the threshold of sediment motion or critical shear stress t * by up to a factor of 2. Although
previous research has shown nets increase t *, the magnitude of resisting force attributed to
individual nets and the threshold of their effect as grain size increases is still unknown. To explore
net strength, I conducted flume experiments at the Stroud Water Research Center in Avondale,
Pennsylvania, where I made direct measurements of the forces acting between nets and individual
sediment particles of various sizes using a strain gage during initial particle motion. 1 paired force
readings with underwater video of each rock to make observations of the stretching, tearing and
detachment of individual nets and measure the increase in force they contribute. Another way I
detected the magnitude of force contributed by caddisfly nets is by comparing the measured peak
forces to an abiotic model used to calculate the peak force without caddisflies to quantify the
difference. Results from measurements made of the force contributed by individual nets and the
difference of peak forces and an abiotic model for individual rock pulled from the bed suggest the
threshold lies between 70 mm and 75 mm b-axis. Net measurements show larger rocks have nets
that are contributing more force because larger rocks allow for larger nets to be built. The influence
of caddisfly nets on bed stability has potentially significant implications for the timing and magnitude
of bedload sediment transport in gravel-bedded rivers.
2019-01-01T00:00:00ZModeling climate change impacts on flooding and community vulnerability Novato, Ca
http://hdl.handle.net/10211.3/213899
Modeling climate change impacts on flooding and community vulnerability Novato, Ca
Goldstein, Suzanne D.
This study investigates the effects of climate change on compound fluvial and coastal
flooding using coupled hydrologic and hydraulic models to examine the changing
physical characteristics and socio-economic impacts of flooding in a small basin typical
of many flood-prone areas on the United States west coast. Novato Creek is located in
Marin County, California along the northeastern edge of San Francisco Bay. With steep,
densely populated communities upstream and major regional transportation and utility
infrastructure in low-lying areas near the bay, the watershed is highly vulnerable to
climate change. Downscaled daily precipitation projections from an ensemble of 10
Global Climate Models indicate that the magnitude of a two-day, 50-year (2% annual
chance of occurrence) storm will increase by an average of 16% ± 6% by mid-century
(2040-69) and 31% ± 8% by late-century (2070-99) under a high emissions (RCP 8.5)
trajectory. These increases in precipitation, combined with sea level rise (SLR)
projections of 0.6 to 1 m (1.9 to 3.4 ft) by mid-century and 1.0 to 1.9 m (3.4 to 5.2 ft) by
late-century, will lead to median increases in flood extent of 42% to 77% by mid-century
and 82% to 83% by late-century. Socio-economic impacts from this compound flooding
are significantly greater than the impacts of SLR or changing precipitation alone. The
total number of people impacted by flooding will increase from 6,500 under historic
storm conditions to at least 9,400 by mid-century and 11,400 by late-century. The length
of roads impacted by flooding will increase 60% to 170%, and as many as 2,400 to 3,250
homes and other buildings will be exposed to flooding. The scale of these projected
impacts makes clear the importance of considering compound flood effects when
planning for climate change adaptation.
2019-01-01T00:00:00Z