Debris flows in the southern Coast Mountains exhibit different dynamic and sedimentologic characteristics, depending on the lithology of their source areas. Fine-textured debris flows originating in the Quaternary volcanic complexes are much more mobile than those originating in the coarse-textured plutonic rocks which form most of this mountain range. Mobility can be described as the velocity of flow, the distance of travel of debris flows, and the slope required to sustain flow. The objectives of this study are to examine the effect of different sediment composition on the mobility of debris flows, and to determine which rheologic models are most applicable for modeling debris flows in these geologic environments. About 25 debris flow events in or adjacent to the southern Coast Mountains were examined, ranging in volume from 10² m³ to over 10⁷ m³. Field methods included sampling of grain-size distribution, measurement of the deposit and channel dimensions, and observation of the stratigraphy of debris flow fans. Shear strength, permeability, and consolidation tests were performed on samples of reconstituted debris, representative of typical fine-textured and coarsetextured debris flows. These samples were also used to model debris flows in a flume. The coarse-textured, plutonic-source, debris flows typically had a distinct, inverselygraded, clast-supported, surface layer of cobbles and boulders. Their deposits tended to be irregular in thickness, with lobes and levees of coarse material. The fine-textured, volcanicsource, debris flows had no such surface layer, and their deposits were generally uniform in thickness and surface morphology. These observations, and corroborating evidence from the flume results, suggest that fine-textured debris flows behave according to the Bingham flow model, while coarse-textured debris flows can be better described by a granular, or dilatant, flow model. A clay content of about 4% in the matrix (sub-4 mm material) is a useful measure to distinguish the two populations. Several debris flow events of intermediate behaviour and sediment composition were also examined. The permeability of the debris, and hence its rate of consolidation, is an important factor controlling mobility. The volume of debris flow events was found to be the most significant factor controlling runout distance.

No description available.

Sea level rise and coastal erosion are two processes which may result in major problems for coastal cities around the world. This is particularly true for Southern and Eastern African cities as they struggle to meet their developmental challenges in addition to sea level rise and coastal erosion. This thesis focuses on three main areas, the analysis of the rates of sea level from tide gauges in the region, the extent of wave run-up on the beach and the development of a simple technical and management framework that managers can apply to assess coastal hazards. The rates of sea level rise in the region vary, Zanzibar, Tanzania reflects a falling sea level at -3:64 plus minus 1:62 mm per year while the highest rate of sea level rise at Diego Garcia, British Indian Ocean Territories is +4:35 plus minus 7:61 mm per year. The rate of sea level rise are dependent on the complex interactions of vertical crustal movements, barometric pressure changes, and the warm Agulhas and cooler Benguela currents. Wave run-up is an indicator of the hazard zone. A number of international wave run-up models were assessed for use in this region and were found to be unsuitable. A new wave run-up model was developed which uses the bathymetric profile as opposed to the beach slope in predicting wave run-up. This model uses the equation Rx H0 = C S2=3, where Rx is the wave run-up height above Still Water Level, H0 is the significant wave height at the closure depth, C is dimensionless coefficient where median values are described by C ' 7:5, S is a representative nearshore slope (S = (hc=xh)). hc is the closure depth and xh the horizontal distance from the waters edge to the closure depth. An assessment of the impacts of sea level rise and wave run-up was undertaken based on a detailed case study of the Durban coastline. The results were incorporated into a standalone freeware viewer tool enabling this information to be accessible to planners, decision makers and the general public. The research has identifed several types of shoreline that are vulnerable to coastal erosion, sea level rise and extreme wave events. Recommendations as to what adaptation measures could be undertaken for the different beach types are proposed. With this information coastal managers and decision makers charged with managing shorelines can take the first step in understanding and adapting into the future. / Thesis (Ph.D.)-University of KwaZulu-Natal, Westville, 2012.

Jekyll Island, Georgia is located within the Georgia Bight, on the Atlantic coast of the United State. In recent history, the Georgia Bight has been less frequently hit by hurricanes compared to other areas along the Atlantic coast. To determine if Jekyll Island has had a more active hurricane past, a paleohurricane record was obtained from the northern tip of the island, within Waterfall Marsh. A 500 year old hurricane record was inferred from the sediment layers obtained from the marsh. In core JE-4, a sandy shell layer containing nearshore foraminifera was observed, providing evidence of a hurricane event. A radiocarbon date of 406 a BP was obtained for the sandy shell layer, providing a minimum age for the hurricane event. A hurricane return interval of one major hurricane per 500 years was also determined for the study area.

The Coast Salish subsistence economy has been characterized by local fishing adaptations to regional ecological variability (Mitchell 1971a.) This dissertation explores the temporal depth of these adaptations in the traditional territory of the Coast Salish, the Gulf of Georgia. Many researchers have used this, Donald Mitchell’s (1971a), model to develop theories of regional cultural development. Many of these interpretations present social complexity or social inequality – a hallmark of Northwest Coast social complexity – as having developed more or less in lock-step with the specialized fishing adaptation described among the Central Coast Salish, around the Fraser River. The temporal depth of this adaptation and the “Diversified” fishing adaptations described among the Northern and Southern Coast Salish, as well as their developmental relationship, are not well understood. In exploring this problem, this study evaluates whether or not the ecological ethnographic model is representative of the archaeology of these cultural subareas. A gap in the regional dataset which corresponds with a large portion of Mitchell’s (1971a) “Northern Diversified” fishing subarea has largely presented a previous study of this type. Recently excavated sites in traditional shíshálh territory provide artifact and archaeofaunal data that fill in this gap. These data are analyzed along with existing data from the Northern subarea and from the Central Gulf of Georgia (River and Straits Fishing subareas). The results of this study significantly broaden our understanding of prehistoric Coast Salish socioeconomic diversity, and test the assumed salmon specialization on the Fraser River and its primacy the development of regional ethnographic characteristics, especially pronounced social inequality. The results also shed light on the prehistoric importance of herring, a decreasingly overlooked resource in Northwest Coast archaeological studies, and advocate for the use of fine mesh recovery for quantifying the relative importance of fish species.

Tree-ring records collected from living mountain hemlock trees in the southern British Columbia Coast Mountains have been used to provide insights into the character of historical climatic fluctuations and the behaviour of individual climate forcing mechanisms. The relatively short-duration of these records limits, however, their ability to describe climate variability and atmospheric processes that change gradually or undergo long-term regime shifts. The objectives of this research were to extend the duration and quality of proxy climate information extracted from mountain hemlock tree-ring chronologies. In coastal British Columbia most existing mountain hemlock tree-ring chronologies extend from ca. AD 1600 to present. To extend the duration of these chronologies, coarse woody debris recovered from the bottom of M Gurr Lake, a high-elevation lake in the vicinity of Bella Coola, British Columbia, was cross-dated to nearby living chronologies surrounding M Gurr lake and increment core samples of ancient trees at Mt Cain on northern Vancouver Island. From this, a regional continuous 917-year long record of radial growth was constructed. The resulting regional chronology was used to construct a 785 year-long proxy record of gridded air temperature anomalies displaying periods of cooler and warmer than average regional air temperatures that contained century-long low frequency trends. Cross-dating and tree morphological evidence of snow avalanche activity displayed within living trees surrounding the lake, and within the coarse woody debris, revealed that low-magnitude avalanches occurred in the winter months of AD 1713-1714, 1764-1765, 1792-1793, 1914-1915, 1925-1926, and 1940-1941. High magnitude avalanche events occurred in the winter months of AD 1502-1502 and 1868-1869. A second objective of the thesis was to investigate the radial growth response of mountain hemlock trees to subseasonal climate variables using standardized ring-width and densitometric analyses. Mountain hemlock chronologies from M Gurr Lake, Cyprus Provincial Park, and Mount Arrowsmith were used to describe the inherent climate-growth trends. Maximum annual tree-ring density values provided a robust data series for constructing site-specific proxy records of late-summer temperature. Annual tree-ring width measurements provided independent proxies of spring snowpack trends. Regionally-derived proxy models indicated that intervals of cooler-than-average and higher-than-average air temperatures correspond to years of higher-than-average average and cooler-than-average snowpacks, respectively. Of note were the significant decreases in air temperature and increases in snowpack depths during the early-1700s and early-1800s coinciding with documented glacier advances in the Coast Mountains. Identification of these subseasonal climate signals within the tree-rings of mountain hemlock trees demonstrates the value of incorporating investigations of multiple tree-ring parameters. / Graduate

No description available.

Graduation date: 1971

Graduation date: 1987

Graduation date: 1983