The long term response of a plume associated with freshwater penetration into ambient, ocean water under upwelling favorable winds is studied using the Regional Ocean Modeling System (ROMS) in an idealized domain. Three different cases were examined, including a shore perpendicular source and shore parallel source with steady winds, and a shore perpendicular source with oscillating alongshore winds. Freshwater flux is used to define plume penetration. Alongshore penetration of buoyant currents is proportional to freshwater input and inversely proportional to upwelling wind stress strength. Strong wind more quickly prevents fresh water’s penetration. Under upwelling favorable winds, the plume is advected offshore by Ekman transport as well as upcoast by the mean flow. This causes the bulge to detach from the coast and move to upcoast and offshore with a 45 degree angle. The path of the bulge is roughly linear, and is independent of wind strength. The bulge speed has a linear relationship with the wind stress strength, and it matches the expected speed based on Ekman theory. Sinusoidal wind leads to sequential upwelling and downwelling events. The plume has an asymmetric response to upwelling and downwelling and fresh water flux is changed immediately by wind. During downwelling, the downcoast fresh water transport is greatest, while it is reduced during upwelling. Background mean flow in the downcoast direction substantially increases alongshore freshwater transport.

Currently there is limited design guidance for calculation that involves an unchannelled balcony spill plume. The current guidance for unchannelled spill plume can be obtained from CIBSE (TM19) and BS PD 7974 (Part 2). The guidance is a result of an analysis performed by Law (1995) on a set of experiments performed by Hansell et al (1993). Recently a series of unchannelled balcony spill plume experiments have been performed by Harrison (2009) at 1/10th-scale as part of a research project. Harrison (2009) developed a simplified design formula to calculate the mass flow rate from unchannelled spill plume. Results from Harrison suggested that an unchannelled balcony spill plume is a complex problem and his experiments were limited by the experimental facility. Harrison (2009) recommended that this problem should be supported with computer modelling for design. Research from Harrison (2009) also resulted in a correlation that can be used to calculate the effective width of an unchannelled balcony spill plume. This research is primarily a numerical simulation of the unchannelled balcony spill plume using Fire Dynamics Simulator 5 version 5.3.0 (FDS 5). FDS 5 was used to model unchannelled balcony spill plume experiments performed by Harrison (2009) at 1/10th-scale. Results from Harrison‟s (2009) experiment were used to verify the results from the FDS simulation. A good match was obtained between experimental results and FDS simulation results. The 1/10th-scale model was extended to full-scale using the scaling laws. Then, the model was used to perform a series of unchannelled balcony spill plume simulations with variables of balcony breadth, compartment opening, fire size and height of rise of the spill plume. Mass flow rate readings from simulations were used to improve the effective width correlations developed by Harrison and an improved effective width correlation was developed. Unchannelled balcony spill plume mass flow rate prediction with the revised effective width correlation was compared with mass flow rate predictions using the effective width correlation from Law (1995) and Harrison (2009).

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Rivers are conduit that transport terrestrial matters to the ocean. Studying how the composition and transport mechanism of terrestrial matters influenced by tide, wave, wind and discharge is an important issue in the disparate of river-sea systems. The aim of this study is to understand the temporal and spatial variability of the grain size distribution of a river plume, using EOF (Empirical Orthogonal Function) to analyze the correlation between environmental processes and suspended sediments. We used CTD and LISST-100 to collect upper-colum profile data at Gaoping River mouth in five (R/V Ocean Research III) cruises from 2005 to 2009. We also deployed an instrumented tetrapods and a moored buoy at the inner Gaoping River mouth and the inner continental shelf off Gaoping River mouth for two days, respectively. In all the upper-column data, the volume concentration increased in surface column when the salinity decreased. The variability of volume concentration are dominant in grain sizes between 10-250 £gm. We used EOF to analyz the time series to investigate the correlations among the volume concentration of 5 grain-size groups (<3, 3-10, 10-63, 63-153, and 153-250 £gm), salinity, water temperature, and alongshore and across-shore winds. The first eigenmode explains about 50 % of the total correlations. This mode describes the dominant influence of the river runoff that affected all the grain-size classes within the plume. This mode suggests that the grain-sizes between 3-250 £gm are of terrestrial origin (low salinity, high water temperature) exported during the ebbing tide. The second eigenmode accounts for about 20 % of the total correlations. This mode describes the dominant influence of the wind. When under the upwelling-favorable across-shore wind, the upwelling brings low temperature and clay-sized suspended sediment from the submarine canyon to the surface. The results suggest that the size-classes greater than 3 £gm are terrestrial suspended sediment and transported by the river plume, the size-classes finer than 3 £gm are mostly from the submarine canyon by the upwelling-favorable winds.

Entrainment velocity, salt flux and the turbulent diffusivity of salt are estimated in the outflow of a small, radially spreading buoyant outflow, just outside of the Teign Estuary mouth, as a means to compare mixing dynamics between very small and larger-scale estuarine and river plumes, and build on a scant knowledge base regarding the former. The analysis was made using a control volume approach, based on the conservation of momentum, volume and salt, from a Lagrangian perspective. Drifting buoys were used to accomplish this. The analysis was based on that employed by McCabe et al. (2008), with some modifications to fit a small-scale outflow, namely: repeat deployments, shorter drifter tracks, and deployment-specific criteria used for choosing the plume base, a step in the analysis used to calculate vertical entrainment, flux and diffusivity. In addition, temperature was used as a proxy for salinity, and this is evaluated in the results. Overall results were compared to a similar study, which was conducted in the Columbia River plume, a system much larger in scale to the Teign. Drifter experiments were conducted on multiple days, under different conditions (i.e. wind, tides, river flow), and those results are discussed briefly, but the focus is on one specific day, April 3, 2014, where conditions most closely matched those of the comparison study, and those results are compared between the two systems. Entrainment velocity was measured along the drifter tracks, in the near-field plume, where shear-induced mixing dominates. Drifter track subsections were chosen so as to avoid source or frontal dynamics, the plume base was chosen for individual deployments as the plume dynamics could change relatively quickly, and repeat deployments were conducted as a way to look at near-field plume evolution over the course of the ebb (and with a smaller plume, time allowed for this) . On April 3, the mean value for entrainment velocity for the four deployments chosen in the Teign outflow was 4.3 x 10-4 ms-1. The mean cast value was slightly higher at 7.6 x 10-4 ms-1, as casts values were typically measured at the beginning of the drifter tracks. Entrainment values at the cast sites were calculated in the same way as the track values, taking plume thickness from hydrographic casts, as a means to evaluate accuracy of track values, which are based on a modelled plume thickness. A rough estimate for the mean entrainment velocity for one pair of drifters used in the Columbia River was 9 x 10-4 ms-1, approximately double that of the Teign, but within the same order of magnitude. Salt flux values ranged from 0-5 x 10-2 psu ms-1 and from 0-3 x 10-2 psu ms-1 for the Teign and the Columbia, respectively, and diffusivities ranged from 0.5-5.8 x 10-2 m2s-1 and from 0.2-9.6 x 10-3 m2s-1. With a similar range of entrainment and salt flux values, and almost an order of magnitude difference between diffusivity values, it was determined that weaker density gradients in the Teign are responsible for the latter, and that this increased level of mixing results in a larger horizontal horizontal salinity gradient, which balances out the terms in the entrainment equation that are related solely to the physical size of the system (i.e. plume thickness, velocity and the vertical salinity gradient). This higher level of mixing of a smaller physical entity, supports the view that smaller plumes mix more thoroughly over a shorter timescale, resulting in a larger impact to the local environment into which they flow.

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