Continental shelves mark the zone between the terrestrial environment and deep marine realm and so are important for understanding sediment transport to the deep ocean. This study investigates the storage and potential record of the terrestrial environment on the Indus Shelf in the North Arabian Sea. The Indus Shelf records the development of clinoform sequences responding to sea level rise since at least the Mid Quaternary. Mapping of sedimentary and structural features established a clear link between sediment transport, deformation and sediment facies. Dome structures in the nearshore zone provide accommodation space on the slope for clinoform development through relative subsidence of neighbouring strata. All clinoforms contain partially eroded topsets formed during sea level fall. Multi-proxy analyses of two cores from the western shelf failed to establish a clear link between the continental record of provenance and weathering from the subaerial Indus Delta and the Indus Shelf system during the Holocene. The dominant source of sediment to the Indus Shelf appears to be erosion of Indus Delta sediments deposited during previous lowstands. During the Early Holocene some sediment is supplied to the north-west shelf from the Makran region due to the strengthening of the Asian Monsoon initiating the northwest to southeast longshore current and mixes with the Indus sediment. Estimates of mineral composition through a six end member algorithm further suggest very little relationship between provenance, weathering and published climatic records before sea level reached present levels. This thesis suggests that the Indus shelf, a high energy, a high sediment supply shelf, stores significant quantities of sediment derived from terrigenous sources. However, erosion and reworking processes mean that the record is not a good indicator of conditions in the terrestrial environment at the time of deposition.

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Using a sediment budget approach, suspended sediment transport dynamics were studied over the 2010 summer runoff season in the 8 km2 West River catchment at the Cape Bounty Arctic Watershed Observatory (CBAWO), Melville Island, Nunavut. Research was carried out in an effort to determine the longer term impacts and response of recent (2007-8) active layer detachments (ALD) on the river system. In 2010, measured ALD inflows contributed 4.7% of the measured sediment yield, a decrease of 13.3% from 2007 when they initially formed. This indicates that while they continue to supply sediment to the main river, the impact they have on sediment fluxes, and hence the sediment budget has diminished, with time. Results from the sediment budget indicate that connectivity and the sediment delivery ratio within the system have also decreased with time. Sediment budget analysis shows that in response to this additional sediment, the West River progressively stores more sediment throughout the season, storing as much as 85% of sediment inflows during baseflow. Sediment was preferentially deposited within the channel, with coarser material deposited in the upper reaches, and finer material deposited in the lower reaches. Similarly, the transported and stored sediment became progressively finer with time, indicating the importance that river competence and wetted perimeter have on sediment transport as the larger sediment was entrained earlier in the season under higher flow conditions when the sediment was accessible, and finer sediment transported later in the season due to decreased competence and reduced accessibility of sediment. This sediment storage is expected to replenish sediment in the channel that is eroded during peak discharge in spring, and also dampens the effects that disturbances have on the sediment budget through storage. Sediment stored in the channel towards the end of the season does not contribute to sediment yield and may prove to be an important source of sediment in future years under late summer rainfall events. / Thesis (Master, Geography) -- Queen's University, 2011-12-08 16:31:48.633

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Intertidal mudflats can experience rapid morphological changes, and are both sources and sinks of fine cohesive sediment within an estuary. Successful environmental management of these regions depends upon in-situ measurements, which help specify the interactions between the active processes and so allow the development of predictive models that the management practices require. The Profiles of Sediment Transport system (POST) has been developed in order to make high frequency measurements of velocity and suspended sediment concentration profiles in very shallow water (i.e. when depth, h < 1.0 m). Electromagnetic current meters and optical sensors were miniaturised to allow measurements within a few centimetres of the sea bed and provide fine scale resolution of vertical profiles. Two in-situ experiments, located in the Severn and Humber estuaries, examined the response of a mudflat to changing environmental factors, and in particular, studied the influence of local waves and tidal currents in very shallow water of depth (h)< 1.0 m. A value of 0.127 Nmˉ²was considered to be representative of the critical erosion shear stress (Tint) at Portishead, while at Skeffling τait was estimated to be about 0.31 Nmˉ². The effects of wave and current action were quantified and expressions were used to describe the relationships between velocity, bed shear stress and concentration. An expression relating near bed concentration to mean velocity (U ) at Skeffling was simply: Concentration (gLˉ¹) = 1.908 U + 0.193 when h< 1.0 m. R² = 0.730 The physical processes causing erosion and deposition across two mudflats have been identified, and the predictive expressions are considered to provide first order approximations for sediment concentrations and transport behaviour, for similar conditions at other North European sites. The results showed that the shallow water periods at the beginning and end of tidal coverage were extremely important in determining the surface character of the mudflat, and any erosion was most marked at these times. Small waves can be crucial to erosion because of their large contribution to the bed shear stresses in shallow water. Ignoring biological and chemical variables (both of which can control of erosion), it is proposed that for typical temperate environmental conditions, some form of mudflat erosion is likely when h< 1.0 m, and either the significant wave height (H2) is greater than 0.25 m, or the near bed velocities exceed 0.2 msˉ¹.

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The development and field testing of a particle tracing technique for the prediction and monitoring of cohesive sediment transport is described. Natural, chemical and water soluble dye tracers have been used for many years to determine water circulation in order to predict sediment transport. Radioactive and fluorescent particles have been used widely to predict sediment particle transport, but have been restricted mainly to non-cohesive sand and gravel transport studies due to the difficulties of preparation, handling, disassociation of the label from the particle and labour-intensive analysis. The development of a fine cohesive tracing technique therefore offered a significant advancement for the understanding and prediction of fine cohesive sediment and pollutant dynamics in aquatic environments if a sediment analogue could be developed. The physical properties, including size, surface charge, fiuorescence and settling velocity of natural fine cohesive sediment were analysed in order to passively and actively adsorb organic fluorescent dyes onto the sediment surface; the tests were largely unsuccessful. The physical properties of artificial fluorescent particles as sediment analogues were examined and found to have a close correlation to natural sediment. Analysis of the fluorescent particles in mud suspensions on an Analytical Flow Cytometer offered an automated and accurate method of tracer concentration determination at low dilutions. A preliminary field study was carried out in a small pool with encouraging results. A study in a shallow freshwater lake was carried out to determine the sediment dynamics in the lake. A depth-averaged model of the wind-driven circulation within the lake was used to interpret the distribution of tracer. Secondary transport and deposition clearly led to an accumulation of sediment and internal loading in the lake driven by hydrodynamical forcing. A study of the particle residence time and deposition-resuspension processes in the turbidity maximum of a macro-tidal estuary. Fluorescent particles were released into the turbidity maximum and were advected down-estuary on the ebb tide and up-esiuary on the flood tide. The residual mass budgets indicated a significant deposition of the particles in the upper estuary at slack high water. The particles were detected in estuarine surface waters 1 week after release. The fluorescent particles behaved in a similar way to the suspended sediment in both the lacustrine and estuarine study and were considered as sutiable tracers for cohesive sediment.