Theses/Dissertations - Geosciences
Permanent URI for this collectionhttps://hdl.handle.net/2104/4784
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Browsing Theses/Dissertations - Geosciences by Author "Allen, Peter M., 1947-"
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Item Assessing the magnitude and frequency of hydrological processes and their effect on threshold channel morphology, North Bosque River, TX.(2021-04-20) Barber, Samuel T., 1995-; Allen, Peter M., 1947-The North Bosque River (NBR) is a dynamic fluvial system experiencing geomorphic change resulting from hydrological and sedimentological influences. This thesis describes the forces that influence hydrological and geomorphological shifts along the NBR corridor, emphasizing the relationship between the frequency and magnitude of high flow events. An increase in NBR mean daily discharge from 5.6 to 8.4 m3/s is attributed to a historical 100-yr flood recorded in late 1991. The NBR’s geomorphic response to flow increases are primarily observed as planform and slope profile changes. Vertical profile changes are limited by the presence of rigid beds, which degrade at a rate of 0.73 mm/yr. Planform erosional assessments indicate that NBR cutbanks are shearing at 0.5 to 0.75 m/y. The NBR’s slope increased and sinuosity decreased from 1995 to 2019. These morphological and hydrological changes characterize the NBR’s response to a historical flood event.Item Factor influencing headcut migration within a cohesive Texas Black-Land gully.(2017-12-01) Auguste, Lance, 1987-; Allen, Peter M., 1947-Gully erosion degrades the Black-Land Prairies (BLP) (Texas), affecting agricultural productivity. It is initiated by rill and inter-rill erosive processes and exacerbated by storm frequency and duration. Few studies have assessed the factors influencing headcut development in cohesive gullies, mainly due to the limitations posed by field instrumentation and the high shear strength of clay soils. Cohesive gullies, e.g. those found in Vertisols may be regarded as an end member gully types in erosion studies. As such, critical assessments of the evolution and failure mechanisms of these headcuts are necessary for channel evolution modeling and determining the potential contribution of these channels to sediment budgets. The El Niño season provided ideal atmospheric perturbations to foster such a study. For the first time, this paper attempts to demonstrate relationships between aerial and subaerial factors influencing gully growth, using new remote sensing methods, hydrology, and in-situ soil properties. As such, the objective is to elucidate the environmental influences leading to erosion in a permanent cohesive gully, by systematically investigating the headcut through space-time and time-lapse observations. Geomorphological processes were validated through offsite observations. Precipitation, migration, discharge and volumetric soil moisture was measured to investigate relationships impacting retreat. Drying days was found to be the most critical factor, with an R2 of 0.95. The total rainfall between migration periods, and discharge at the over-fall also critically informed migration, with R2 values of 0.89, and 0.78, respectively. A vertical zonation of the headcut was found based on soil geotechnical properties that produced a distinct failure mechanism. Tridimensional photo reconstruction (3D PR) (Structure-From-Motion) techniques were used for topographic analysis.Item Methods of determining stream setback corridors in urban watersheds from remotely sensed data in the Dallas metropolitan area, Texas.(2010-02-02T20:03:48Z) Schreiner, Matthew R.; Allen, Peter M., 1947-; Geology.; Baylor University. Dept. of Geology.Bank stability in urbanized streams is worsening in response to increased runoff, causing unprecedented stream erosion. Eroding banks pose a serious threat to existing structures prompting cities to create buffer zone ordinances to prevent the loss of future structures. Unfortunately, most ordinances probably misjudge buffer zone widths due to the lack of sufficient topographic accuracy for their delineation. However, this study utilizes observations based from remotely sensed data, such as Light Detection and Ranging (LiDAR) with higher accuracy, as well as geological parameters such as channel material. Stream setbacks are easily calculated using computer-aided mapping technology, through the use of remotely sensed data and setbacks can be determined and mapped as corridors with minimal field checking. This study evaluates the overall accuracy of this methodology as compared with values acquired in the field. The results show that the LiDAR data, while being a relatively good fit to the field data, can misrepresent stream setbacks in areas of high relief, most likely due to the smoothing algorithms used in the post-processing of the raw LiDAR data, and field checking is advocated.Item Modeling channel erosion in cohesive streams of the Blackland Prairie, Texas at the watershed scale.(2008-10-02T18:43:42Z) Capello, Stephanie V.; Allen, Peter M., 1947-; Geology.; Baylor University. Dept. of Geology.Stream bank erosion is a product of submerged and subaerial processes. The goal of this research was to assess the application of the submerged jet test to predict erosion of cohesive stream banks in the Blackland Prairie of North Central Texas, an area with over 40% of the State’s population. In situ erosion monitoring was conducted by utilizing erosion pins and water level loggers at seven field sites with contributing drainage areas of 5-239 square kilometers. Erosion pins were placed at two locations on the cutbank wall and monitored over one year. Erosion rates during the monitoring period were a function of bank height and flow duration. Submerged jet test values from samples taken at the same locations as the erosion pins predicted erodibility of the material ranged from 0.0034-0.0065 cm3/N-s. Erosion pins indicated 30.35-572.00 mm of loss. The predicted erosion coefficients from the jet test, tractive force, and cumulative flow duration was within 31% of the field erosion. This study evaluates the first in situ testing of the erodibility of cohesive stream banks with cumulative flow duration, cumulative tractive force, and subaerial processes.Item Streambank erosion assessment : application of dendrogeomorphology, numerical watershed modeling, and model characterization.(2016-07-06) Norair, Stephen G., 1990-; Allen, Peter M., 1947-This project uses a dendrogeomorphic method to assess streambank erosion at two ungauged streams in Central Texas: Cedar Creek, a small urban stream, and Mill Creek, a medium-sized rural stream. This method yields better erosion rate estimates than typical one- to two-year erosion-pin studies, while also offering insight into the magnitude and variability of sub-aerial processes, mass wasting, and fluvial entrainment. We used the results from this assessment in tandem with data gathered from available literature to parameterize, calibrate, and interrogate the watershed model SWAT-DEG. Through the linear analyses available in the software suite PEST, model predictive uncertainty, prediction sensitivity to parameters, and observation worth were assessed. The synthesis of the dendrogeomorphic channel assessment and SWAT-DEG modeling used in this study outline a method for characterizing past erosion and predicting future erosion accurately and efficiently.