Understanding the extent to which human activities impact surface water resources has become increasingly important as both human population growth and related landscape changes impact water quality and quantity across varying geographical scales. Skypark, Santa’s Village is a 233.76-acre tourism-based outdoor recreation area located in Skyforest, California residing within the San Bernardino National Forest. The park is situated at Hooks Creek, the headwaters of the Mojave River Watershed, and is characterized by a diverse landscape that includes forest cover and human development, including impervious surfaces, a restored meadow, and recreational trails. In 2016, Hencks Meadow was considered degraded by human activity and restored by the Natural Resources Conservation Services (NRCS) using best management practices (BMPs) to manage stormwater runoff and mitigate pollutants entering recreational downstream surface water. Three BMP detention basins were constructed to store and improve water quality from stormwater runoff. The purpose of this study is to observe the extent to which the engineered BMP detention basins design were effective in mitigating stormwater pollution from entering Hooks Creek. Over a six to eight month period (January to August), ponds were tested in situ bi-weekly for temperature (ºC), dissolved oxygen (mg/L), pH, turbidity (NTU), conductivity (µS/cm), nitrate (mg/L), and ammonium (mg/L), with additional laboratory tests for total suspended solids (mg/L), total dissolved solids (mg/L), chemical oxygen demand (mg/L), total coliform (MPN/100mL), Escherichia coli (MPN/100mL), and trace metals (µg/L). The results of this study support that the BMP design is improving surface stormwater runoff from impervious surfaces before it enters Hooks Creek. Findings could also promote the design and implementation of stormwater BMP detention basins at other site locations where water degradation is evident. Furthermore, this research can be used to promote the necessary improvement of water quality and quantity on a widespread geographical scale.

Abstract not available

This thesis consists of six published papers. The present-day stress tensor has been determined using petroleum well data in the Gippsland and Otway Basins in Southeast Australia (Papers 1 and 4) and the Cooper Basin in Central Australia (Paper 5). In the Gippsland Basin, the present-day stress regime is transitional between one of reverse and strike-slip faulting and the maximum horizontal stress (SHmax) is oriented ~139°N. The present-day stress regime in the Victorian sector of the Otway Basin is also transitional between one of reverse and strike-slip faulting and SHmax is oriented ~135°N. Horizontal stresses are lower in the South Australian sector of the Otway Basin where the stress regime is one of strike-slip faulting and SHmax is oriented ~124°N. The orientations of SHmax in Southeast Australia are consistent with focal mechanism solutions, neotectonic structures and modelling of plate-boundary forces (Paper 4). Closure pressures from mini-frac injection tests are commonly used to determine the minimum horizontal stress (Shmin) magnitude. However, in high stress basins such as the Cooper and Gippsland Basins, these pressures may not reliably yield Shmin (Papers 2 and 5). In the Cooper Basin, high closure pressures (>18 MPa/km) were observed in tests where pressure-declines indicated complex hydraulic fracture growth. Closure pressures in these injections are unlikely to be representative of Shmin. They are believed to reflect the normal stress incident on pre-existing planes of weakness that are exploited by hydraulic fluid during the mini-frac injection (Paper 5). Sub-horizontal fabrics that are open at the wellbore wall were observed on image logs in the Cooper and Gippsland Basins (Papers 2 and 5). This fabric is believed to be at least partially responsible for the complex growth of hydraulic fractures observed in the Cooper Basin. The occurrence of these sub-horizontal fabrics and knowledge of rock strength have been used to constrain the magnitudes of SHmax and Shmin independently of mini-frac injections in the Cooper and Gippsland Basins (Papers 2 and 5). The present-day stress tensor is often quoted as a single gradient at a sedimentary basinor petroleum field-scale. Image logs and mini-frac data from Central and Southeast Australia indicate significant stress differences between stratigraphic units (Papers 3 and 5). Finite element modelling of the stress distribution between interbedded sands and shales in the Gippsland Basin indicates that stress is ‘partitioned’ to ‘hard’ lithological units in high stress areas. This accounts for the observation that borehole breakout only occurs in hard, cemented sandstones in the Gippsland Basin (Paper 3). A generic ‘mechanical stratigraphy’ derived from knowledge of wellbore failure (from image logs), rock strength and rock properties in individual rock units in the Cooper Basin allows an approximation of the present-day stress-state to be made directly from image-logs for individual rock units prior to mini-frac injection (Paper 6). This is important for predicting and understanding hydraulic fracture growth and containment. When considered together, the papers comprising this thesis provide significant new data on the orientation and magnitude of present-day stresses in Central and Southeast Australia. They also provide insight into the tectonic origin of those stresses and their distribution within sedimentary basins. In particular the papers develop and use new methods for constraining the present-day stress in regions of high tectonic stress. They also discuss implications for problems in petroleum development including wellbore stability and hydraulic fracturing. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1283781 / Thesis(Ph.D.) -- Australian School of Petroleum, 2007

Maps in pocket inside back cover. / Includes published papers and abstracts of works by the author / "November 2003" / Includes bibliographical references. / Various paging : ill. (chiefly col.), maps, plates, charts (some folded) ; 30 cm. + 2 scaled seismic survey maps / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, School of Earth and Environmental Sciences, National Centre for Petroleum Geology and Geophysics and Discipline of Geology and Geophysics, 2004

pas de résumé

The objective of this thesis is to study two Basins of the Gulf of Guinea (GoG), namely the Dahomey and the Liberian Basins. These Basins are located in the northern part of the GoG, where oil and gas exploration has significantly increased in the last 10 years or so. We proposed geological descriptions of these two Basins. The key characteristics of the two models are the presence of channels and pinch-outs for depths of between 1 km and 2 km (these values are rescaled for our numerical purposes to 600- m and 700-m depths) and normal faults below 3 km (for our numerical purposes we use 1 km instead of 3 km). We showed that these models are consistent with the plate tectonics of the region, and the types of rocks and ages of rocks in these areas. Furthermore, we numerically generated seismic data for these two models and depth-migrated them. We then interpreted the migrated images under the assumption that the geologies are unknown. The conclusions of our interpretations are that we can see clearly the fault systems in both models. However, our results suggest that seismic interpretations of the channels and pinch-outs associated with the geology of the Dahomey and Liberian Basins will generally be difficult to identify. In these particular cases, we missed a number of channels and pinch-outs in our interpretations. The limited resolution of seismic images is the key reason for this misinterpretation.

Zugl.: Bonn, University, Diss., 2004.

The West Antarctic Ice Sheet (WAIS) is mostly grounded in broad, deep basins (down to 2.5 km below sea level) that are stretched between five crustal blocks. The geometry of the bedrock, being mostly below sea level, induces a fundamental instability in the WAIS through the possibility of runaway grounding line retreat. The crustal environment of the WAIS further influences the ice sheet’s fast flow through conditions at the ice-bedrock boundary. This study focuses on understanding the WAIS by examining the subglacial geology (such as volcanoes and sedimentary basins) at the icebedrock boundary and the continent’s deeper crustal structure- primarily using airborne gravity anomalies. The keystone of this study is a 2004-2005 aerogeophysical survey over one of the most negative mass balance glaciers on the continent: Thwaites Glacier (TG). The gravity anomalies derived from this dataset- as well as gravity-based modeling and spectral crustal boundary depth estimates- reveal a heterogeneous crustal environment beneath the glacier. The widespread Mesozoic rifting observed in the Ross Sea Embayment (RSE) of West Antarctica extends beneath TG, where the crust is ~27 km thick and cool. Adjacent to TG, spectrally-derived shallow Moho depths for the Marie Byrd Land (MBL) crustal block can be explained by thermal support from warm mantle. I assemble here new compilations of free-air and Bouguer gravity anomalies across West Antarctica (from both airborne and satellite datasets) and re-interpret the extents of West Antarctic crustal block and their boundaries with the rift system. Airy isostatic gravity anomalies reveal that TG is relatively sediment starved, in contrast to the sediment-rich RSE. TG’s fast flow velocities could be sustained in this sediment poor environment if higher heat flux in MBL was providing an ample source of subglacial melt water to the glacier. The isostatic anomalies also indicate that TG’s outlet rests on a bedrock sill that will impede future grounding line retreat (up to ~100 km) and temporarily stabilize the glacier. / text

Because the volume of flow through an inlet is proportional to the tidal range and the area of the tidal basin, Texas tidal inlets have some of the largest tidal basins relative to their entrance area of any inlet. Matagorda Bay at Pass Cavallo has an area of about 200 square miles, but only a mean diurnal tidal range of about 1.1 feet. From tide gage records the most important events modifying tidal currents in Pass Cavallo are the numerous wind tides each year that occur most frequently during the cooler months, November through May. Wind tides are most noticeable in Matagorda Bay because the astronomical tidal range is small, the fetch long (10-20 miles) and the depth only about 12 feet. Hurricanes and river floods that would raise water levels in Matagorda Bay by even 0.5 foot occur too infrequently to affect equilibrium conditions in the inlet. Pass Cavallo has passed through three time periods since 1856: 1856-1930, 1930-1965, and post 1965. Each time period was characterized by a different, and subsequently smaller tidal discharge, cross-sectional area and tidal channel length. The tidal discharge decreased between 1929 and 1935 when the Colorado River delta cut off part of east Matagorda Bay to reduce the tidal area of Matagorda Bay, and in 1965, the Matagorda Ship Channel was dredged across Matagorda Peninsula to reduce the volume of water passing through Pass Cavallo. Other features that changed with decreasing discharge, but remained stable during each time period, were the channel pattern, and location and shape of the Gulf bar and Pelican Island. During all three periods Pass Cavallo maintained stable cross-sectional shape, and tidal flow by-passing characteristics, except during the post 1965 when neither tidal flow by-passing nor bar by-passing were dominant. Since 1856 Pass Cavallo has remained geographically stable relative to its width. The axial trough has migrated southwestward about 1000 feet during the past 100 years--or about 1/9th the distance between Matagorda Peninsula and Matagorda Island. Shorelines adjacent to the inlet also have tended to move southwestward, but at a faster rate than the axial trough. Along the western side of the pass, shoreline erosion is related to jetties interrupting sediment transport southward from the western shoreline of Matagorda Bay, and to storms eroding the constructional beach extending northward from Matagorda Island. The modern flood delta at Pass Cavallo consists of a large, sandy platform, that is lobate into Espiritu Santo Bay with salt marsh, storm-tidal flats and tidal channels. The flood delta is located to the side of the channel pattern of Pass Cavallo, and appears to be active only during the high tides of hurricanes, tropical storms and "northers". There are three informal physiographic provinces on the flood delta, each one reflecting a different sediment supply and energy regime inherent in each bay and in the Gulf. 1) The Gulf of Mexico Province has the largest and best-developed intertidal beaches, surge channels, storm-tidal flats and mounds of all three provinces. Sand is the dominant sediment. 2) Matagorda Bay Province includes large marsh islands and tidal channels with fewer large vegetated mounds. Shell is very abundant in mounds, and a storm-tidal flats contain more mud and encroaching salt marsh than in the Gulf province. 3) Espiritu Santo Bay Province is composed mostly of sandy mud or muddy sand sediment, with the exception of erosional shell beaches that face a north or south fetch of 1 to 2 miles. This is the richest area biologically, consisting mostly of salt marsh and grassflats. / text

Fifty-three basins with area less than 9.40 km² were mapped from 1:25,000-scale aerial photographs to provide data on basin morphometry. A significantly larger number of first-order streams exist than are expected according to the regression of stream number on order for each basin. This is attributed to the incorporation of recently formed gullies into the stream network as first-order streams. Most drainage density (Dd) values are in the coarse texture category (Dd<5.0 km/km²). Higher values of Dd correspond to areas of shallow soils. Total stream frequency (F[subscribe t]) and first-order stream frequency (F₁) are closely correlated with Dd (r=+0.86 and r=+0.89, respectively), but third-order stream frequency (F₃) is not (r=+0.70). F[subscribe t] is related to Dd as follows: F[subscribe t]=0.704 (Dd)²̇⁰⁸. Values of ruggedness number (HDd) and basin magnitude indicate that all basins are high-flood potential basins. This imposes serious limitations on the development of the watershed as a whole. Weighted mean percent silt-clay (M) and channel width-depth ratio (F) for 21 cross sections of stream channels were used to define cross section stability. Catchment area above each cross section is related to its stability. As area increases cross sections change from degrading to aggrading to stable conditions. There is a more gradual increase in F with decreasing M than in streams in the mid-western United States. This is attributed to the vigorous vegetation which stabilizes channel banks in the Mandaguari watershed. Recent climatic changes in the region rendered colluvial deposits susceptible to increased erosion under the present subtropical (Cwa) climate. When saturated, the latosols and podzols there are easily eroded owing to their low cohesion (PI=0-15). Recent deforestation and seasonal burning of pastures probably exacerbate this condition, contributing to the erosion of hillsides and the formation of gullies. Large, aggressive gullies (voçorocas) 10-15 m deep and 30-40 m wide occur in association with urban centers. Management of the Riberão do Mandaguari watershed should be based on considerations of (1) threshold conditions for instability of stream channel cross sections and soils and (2) complex responses of the watershed. Recommended actions are reforestation of slopes at and above the point of maximum profile steepness, induced incision of channel filling deposits, and control of runoff from urban centers. / text