In classic river literature, flow around a bend is directed toward the outer bend at the surface and towards the inner bend at depth, owing to the lateral momentum balance between the centrifugal force and the pressure gradient resulting from the lateral setup. However, in estuaries, salinity differences along and across the channel also affect the hydrodynamics. During a field campaign led by Dr. Wouter Kranenburg, we observed classical lateral circulation during ebb tide and reversed lateral circulation during most of the flood tide. This reversed flow mechanism may have implications on estuarine channel morphodynamics, which is important for understanding the resiliency of estuaries with respect to anthropologic effects such as rising sea levels due to climate change.
Over long periods of time, the salinity distribution in an estuary is determined by the balance between river outflow, which advects salt out of the estuary, and estuarine dispersion, which is a diffusive mechanism bringing salt into the estuary. While we can determine the estuarine dispersion rate based on the river outflow and salinity time-series in an estuary, we need higher resolution spatial and temporal data to resolve the individual mechanisms that contribute to the total dispersion rate. We conducted a field campaign to determine the contribution of tidal tributary creeks to the total estuarine dispersion. In the system we studied, the creeks can account for about half of the total estuarine dispersion rate. The estuarine dispersion is important because it controls the salinity intrusion, which acts as a control on both ecology and freshwater sources.
In short, tidally-dominated estuaries, circulation and mixing is dominated by processes which act on a tidally-varying timescale (<12 hours) rather than on a tidally averaged (>12 hours). Using an idealized model built with the Regional Ocean Modeling System (ROMS), I applied a semi-Lagrangian to analyze dispersive salt fluxes and determine the relative contributions of various topographic regions to the the estuarine salt balance. Notably, by using a semi-Lagrangian approach, I quantify how dispersive processes outside the mouth of an estuary drive the salt flux inside the estuary. This research therefore provides a direct linkage between mixing and circulation patterns in an estuary and the coastal ocean.
With climate change and increased anthropologic activities on the rise, coastline environments and communities will face higher threats. Researchers are considering many forms of "green infrastructure" to protect against storm surge, including coral reefs, seagrasses, and mangrove trees. Mangroves dissipate wave energy because of flow through their complex prop root system, which effectively enhances turbulent dissipation. Working with Dr. Heidi Nepf, I conducted lab experiments to determine the drag coefficient of mangrove trees. The drag coefficient is important to calibrate numerical models that can be used to plan future mangrove reforestation projects.
This research was conducted with Dr. Jorge Abad. Analyzing satellite imagery on with ArcGIS, I worked to create a baseline study for the morphodynamics of the Peruvian Amazon River by performing a spatial and temporal analysis of the river system from 1985-2010. The purpose of this research is to understand the migration of the river and the processes that form the river's unique geomorphic characteristics. During the CREAR-ED-SPA course, I learned more about the importance of the river to the surrounding region.This research will be important for future development in the Amazon region, because the migration of the river will have huge implications on navigation and accessibility.
My senior design group worked in partnership with Lisa Hollingsworth-Segedy from the Pittsburgh Office of the American Rivers organization to perform the design work necessary for the permitting process to remove the Franklin-Glass Dam in Renfrew, PA. This dam, located on Connoquenessing Creek just downstream of the junction with Thorn Creek, is being removed to restore the river to free-flow conditions, allowing for improved fish passage and sediment transport. This project was incredibly multi-disciplinary, requiring work in hydraulics, ecology, environmental engineering, and construction management. My team worked with scientists and engineers from the PA Fish & Boat Commission and the PA Department of Environmental Protection to satisfy permitting requirements.
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