Catchment Hydrology In The Anthropocene: Impacts Of Land-Use And Climate Change On Stormwater Runoff

Urbanization and climate change are associated with extreme changes to hydrologic processes that alter the amount and timing of runoff delivery in the Anthropocene. This dissertation research examined the degree of urbanization, climate change, and hydrologic responses in Rocky Branch Watershed (RBW), a small, highly urbanized catchment with dense vegetation canopy in Columbia, South Carolina. This dissertation is composed of three parts: (1) an automated algorithm for mapping building impervious areas (BIA) from remote sensing data for estimating percent impervious area (PIA), (2) a paired watershed study contrasting a forested with an urban watershed, and (3) a hydrologic simulation model to compare land-use and climate changes in an urban watershed. One key cause of hydrologic change, and also a measure of the degree of urbanization, is the PIA. However, mapping PIA under dense vegetation canopy is a challenge. Moreover, hydrologic changes to surface runoff in response to high PIA include an increase in peak flows and a decrease in peak flow arrival times. Although these relationships are general understood, details are missing—especially for small watersheds. This research presents a new building extraction approach that is based on and optimized for estimating building impervious areas (BIA) for hydrologic purposes. The Building Extraction from LiDAR Last Returns (BELLR) model, uses a non-spatial, local vertical-difference filter on LiDAR point-cloud data to automatically identify and map building footprints under dense vegetation canopy. The BELLR- estimated BIAs were tested using two different types of hydrologic models to compare BELLR results with results using the National Land Cover Database (NLCD) 2011 Percent Developed Imperviousness data. The BELLR BIA values provide more accurate results than the use of the 2011 NLCD PIA data in both models. Comparisons between RBW and a forested watershed under different land-use conditions utilized field measurements of rainfall and streamflow to characterize storm hydrographs in order to quantify hydrologic responses to anthropogenic changes in small, heavily urbanized watersheds. It contrasts peak discharges, stormflow durations, volumes of storm water, shapes of storm hydrographs, and runoff coefficients generated by a variety of storm events between the two watersheds. The EPA Storm Water Management Model (SWMM) was used to study the effects of urbanization and climate change on stormwater in RBW. SWMM was applied to a series of scenarios to compare relative effects of projected PIA and climate-change scenarios on runoff for the near term (2035) and far term (2060). This analysis showed that climate change has generated a greater impact on runoff than urbanization

Weakly- and Semi-Supervised Probabilistic Segmentation and Quantification of Ultrasound Needle-Reverberation Artifacts to Allow Better AI Understanding of Tissue Beneath Needles

Ultrasound image quality has continually been improving. However, when needles or other metallic objects are operating inside the tissue, the resulting reverberation artifacts can severely corrupt the surrounding image quality. Such effects are challenging for existing computer vision algorithms for medical image analysis. Needle reverberation artifacts can be hard to identify at times and affect various pixel values to different degrees. The boundaries of such artifacts are ambiguous, leading to disagreement among human experts labeling the artifacts. We propose a weakly- and semi-supervised, probabilistic needle-and-reverberation-artifact segmentation algorithm to separate the desired tissue-based pixel values from the superimposed artifacts. Our method models the intensity decay of artifact intensities and is designed to minimize the human labeling error. We demonstrate the applicability of the approach and compare it against other segmentation algorithms. Our method is capable of differentiating between the reverberations from artifact-free patches as well as of modeling the intensity fall-off in the artifacts. Our method matches state-of-the-art artifact segmentation performance and sets a new standard in estimating the per-pixel contributions of artifact vs underlying anatomy, especially in the immediately adjacent regions between reverberation lines. Our algorithm is also able to improve the performance downstream image analysis algorithms

Entanglement Entropy of Topological Orders with Boundaries

In this paper we explore how non trivial boundary conditions could influence the entanglement entropy in a topological order in 2+1 dimensions. Specifically we consider the special class of topological orders describable by the quantum double. We will find very interesting dependence of the entanglement entropy on the boundary conditions particularly when the system is non-Abelian. Along the way, we demonstrate a streamlined procedure to compute the entanglement entropy, which is particularly efficient when dealing with systems with boundaries. We also show how this method efficiently reproduces all the known results in the presence of anyonic excitations.Comment: 29 pages, 11 figure

Modular parallel transport of multiple intervals in 1+1-dimensional free fermion theory

Modular parallel transport is a generalization of Berry phases, applied to modular (entanglement) Hamiltonians. Here we initiate the study of modular parallel transport for disjoint field theory regions. We study modular parallel transport in the kinematic space of multi-interval regions in the vacuum of 1+1-dimensional free fermion theory--one of the few theories for which modular Hamiltonians on disjoint regions are known. We compute explicitly the generators of modular parallel transport, and explain why their relatively simple form follows from a half-sided modular inclusion. We also compute explicitly the curvature two-form of modular parallel transport. We contrast all calculations with the expected behavior of modular parallel transport in holographic theories, emphasizing the role of non-local terms that couple distinct intervals.Comment: 24 pages, 5 figure