Browsing by Author "Butler, Karl E."

Now showing 1 - 5 of 5
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    Electrical resistivity imaging for embankment seepage monitoring
    (University of New Brunswick, 2024-04) Danchenko, Dmitriy; Butler, Karl E.
    Measurements of electrical resistivity variations are of special interest for non-invasive investigation of concentrated seepage through embankment dams . An experimental resistivity monitoring system is in development at the Mactaquac Hydroelectric Generating Station in New Brunswick, Canada. With 123 electrodes distributed over a 70 m x 25 m area adjacent to a concrete sluiceway structure, the system runs autonomously each night, collecting over 7000 apparent resistivity measurements. Annually the resistivity of water in the reservoir varied by nearly a factor of four, providing a strong signal for use as a tracer to highlight regions that appear to have experienced preferential water flow. Order-of-magnitude estimates for seepage flux are calculated by analyzing the time lag between resistivity changes measured in the reservoir and the dam core. The results suggest that the electrical resistivity imaging approach is feasible for seepage monitoring at water retaining structures, even in an electrically noisy environment.
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    Extracting subtle anomalies from distributed temperature sensing data for dam seepage investigations
    (University of New Brunswick, 2025-08) de Gante Carrillo, Emanuel; Butler, Karl E.; MacQuarrie, Kerry T.B.
    Fibre optic Distributed Temperature Sensing (DTS) systems are widely used in dams to measure temperature and detect leaks or concentrated seepage. Temperature anomalies caused by advective heat transport of water distort normal temperature patterns, signaling potential leakage. This research develops data visualization and processing techniques to analyze over 10 years of DTS data acquired at the Mactaquac Dam. The dataset shows strong seasonality from conductive heat exchange with air-exposed surfaces and the reservoir. Two approaches are applied to extract subtle anomalies. The first calculates the temperature gradient along the DTS cable, using median filtering to suppress noise and highlight sharp or short wavelength variations. The second, the DBM (deGante-Butler-MacQuarrie) algorithm, adapts the Karhunen-Loève Transform from seismic data processing to estimate and remove seasonal effects as a function of depth, revealing subtler patterns. New visualization methods, including temperature–depth and gradient-depth display inspired by seismic traces displays enhance interpretation.
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    Synthetic aperture radar for structural mapping and landslide risk assessment
    (University of New Brunswick, 2025-08) Fobert, Mary-Anne; Spray, John G.; Singhroy, Vern; Butler, Karl E.
    In 2019, Canada launched the RADARSAT Constellation Mission (RCM). This constellation is comprised of three functionally identical synthetic aperture radar (SAR) satellites. On board each satellite is a SAR sensor equipped with the first ever operational compact polarization (CP) architecture. This dissertation focuses on the assessment of this CP mode, and the use of traditional SAR for structural mapping and geohazard risk assessment. Results presented herein provide the first assessment of both simulated and real CP data, in comparison to full polarimetry (FP) and circular polarimetry, for surficial lineament mapping. Comparisons of the different polarization architectures were made based on their ability to extract inferred faults related to linear shorelines, linear escarpments, and those that were manually identified over the Manicouagan impact crater in Québec, Canada. In agreement with prior assessments of CP for other applications, this dissertation shows that CP remains complementary to FP. CP does not outperform FP but rather can provide similar information. To extend the use of SAR for the structural mapping of the Manicouagan structure, a second study was employed where the use of traditional SAR, integrated with satellite optical and terrain information, was explored for the creation of a lineament map. This map was centered on Manicouagan and covered an area close to 100,000 km2. It was constructed through the development of a semi-automated, iteratively executed, line-linking algorithm. A comparison of this map with published maps of faults, folds, and lineaments yielded an overlap of 45% (~5,000 km). The constructed map assisted in the identification of Manicouagan’s impact related morphometry, including its polygonal shorelines, concentric and radial faults, central uplift, and an outer ring. The last study in this dissertation focused on the use of traditional SAR for geohazard risk assessment. The widely used interferometric SAR (InSAR) technique was applied over the tropical island of Dominica. Using deformation maps and time series analysis, strategies for integrating this information into landslide susceptibility and landslide inventory mapping were developed during this study. Kinematic dynamics of slope failure and an observation on the impact of soil type and slope gradient are also presented.
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    Understanding Spatiotemporal Variations in Soil Moisture Associated with Tile Drains Using Electrical Resistivity Imaging
    (University of New Brunswick, 2022-04) Dobson, Troy J. A.; Butler, Karl E.; Danielescu, Serban
    Agriculture in the Canadian Atlantic provinces is influenced by a humid continental climate, hilly landscape, and soil derived from glacial till. As a result, many regions suffer from poorly draining soil. Tile drains have gained popularity since the 1970s for removing excess moisture and increasing field productivity. The goal of this study was to use time-lapse electrical resistivity imaging (ERI) to resolve, in space and time, how well tile drains help to remove excess water from sandy loam agricultural soils underlain by low permeability glacial till in the Saint John River valley at Fredericton, New Brunswick. One of the plots was equipped with tile drains at approximately 90 cm depth, while the other was not. Time-lapse ERI successfully inferred temporal changes in saturation in both fields. ERI-derived estimates of changes in water storage were in good agreement with those made using capacitive moisture sensors except immediately following intense rainfalls at the shallowest sensor locations (15 cm depth) where installation artifacts may have affected both methods. Results indicated that the tile-drained field (TDF) showed significantly faster drying immediately following rainfall, and that drying extended to greater depth after prolonged periods compared to the non-tile-drained field (NTDF). Up to 20% desaturation was observed after a week of drying in the TDF during the late summer period. Three different methods - soil water balance, moisture sensors, and time-lapse ERI - were used to estimate changes in water storage in the two fields during spring 2020. ERI-derived estimates of water gain during an intense rain event indicated that the TDF gained an amount nearly equal to the 25 mm rainfall, while the NTDF gained very little water, consistent with its higher antecedent water content and measurements of surface runoff. Following the rainfall event, with both fields near full-saturation, ERI indicated that the tile drains improved the field-scale drying by a factor of 3 after 48 hours. Beyond 48 hours, the effect of the tile drains was less noticeable as the two fields lost water at similar rates.