Verification of a Three Dimensional Advection Dispersion Model Using Dye Release Experiment

The study aims to investigate transport processes within the entrance of a coastal lagoon through estimating the advectiondispersion coefficients of the estuary. To this end, an extensive observational data set including water level variation and current has been used for the hydrodynamic calibration of the model. Simulation of water quality variation with time requires mathematical modelling based on the advection and dispersion phenomenon. The advection-dispersion model is setup using a MIKE3 software platform. The model is calibrated using data obtained through monitoring the dilution and movement of a tracer (Rhodamine WT), which is introduced into the water column during a number of experiments at various locations within the study area

Coastal saltmarsh managed realignment drives rapid breach inlet and external creek evolution, Freiston Shore (UK)

The creation of saltmarsh through the managed realignment of sea defences, implemented in NW Europe as a sustainable coastal defence option, represents a substantial hydrodynamic perturbation to the local coastal system. The impact of a significantly increased tidal prism on hydromorphological features was investigated at Freiston Shore, Lincolnshire UK. Local tidal conditions and inadequate drainage at this realignment trial contributed to significant channel erosion due to the establishment of water surface slopes and pooling between the newly realigned site and the adjacent intertidal zone. Very high spatial resolution aerial photography and blimp photography were used to monitor inlet evolution from breaching in August 2002 to March 2008, showing a highly non-linear response with breach channels increasing in width by up to 960% within 2.5. months. Airborne laser scanning/LiDAR and terrestrial laser scanning quantified breach channel volume increases, showing a similar pattern. Breach channel evolution did not follow established tidal prism-channel width/cross-sectional area relationships that are often used to guide realignment design. Pre- and post-breach rates of external creek morphology change between 1999 and 2006 were also quantified, with intertidal creeks attached to the breach channels increasing significantly after realignment in both width and depth. This study highlights the physical processes affected by managed realignment, and the importance of understanding the causes of complex water surface slopes at multiple scales. © 2013 Elsevier B.V

Groundwater table response to sea level rise and its impact on pavement structure

It has been predicted that sea level will rise about 0.8 m by 2100. Consequently, seawater can intrude into the coastal aquifers and change the level of groundwater table. A raise in groundwater table due to seawater intrusion threats the coastal infrastructure such as road pavements. The mechanical properties of subgrade materials will change due to elevated rise of groundwater table, leading to pavement weakening and decreasing the subgrade strength and stiffness. This paper presents an assessment of the vulnerability of subgrade in coastal areas to change in groundwater table due to sea-level rise. A simple bathtub approach is applied for estimating the groundwater level changes according to sea-level rise. Then the effect of groundwater level changes on the soil water content (SWC) of a single column of fine-sand soil is simulated using MIKE SHE. The impact of an increase in moisture content on subgrade strength/stiffness is assessed for a number of scenarios

Direct measurements of the bottom friction factor beneath surface gravity waves

This paper describes a detailed experimental study of the laminar and turbulent oscillatory boundary layer developed under the action of waves for the purpose of evaluation of bottom energy dissipation. The measurements were conducted on hydraulically smooth and immobile rough beds and under both monochromatic conditions and a spectrum of waves in a 50 m long wave flume. Bottom friction was measured in two different ways: (i) by a flush mounted shear plate, developed as part of the project and set at the bottom of the flume, (ii) by using the momentum integral equation and the measured velocity profile within the boundary layer. The velocity profile within the boundary layer was measured using a Laser Doppler Anemometer. The roughness geometry was chosen to simulate both rough flat and rippled beds. With respect to the dissipation under a spectrum of waves, the results show that a spectrum of waves and a monochromatic wave whose maximum bottom velocity is 1.88 times the root mean square of the bed velocity of the spectrum, dissipate the same amount of energy. As a consequence, measurements of energy dissipation for monochromatic waves can be related to spectral conditions. The results for monochromatic waves were found to be in good agreement with the existing formulae for the bottom friction factor, which have mainly been based on experimental results in water tunnels or over oscillating trays. Therefore, it was concluded that the secondary effects due to the nonuniformity of the bed velocity in the horizontal direction, which can be observed under real waves, does not have substantial influence on the bed friction factor. In addition, it was concluded that the nonlinearity of waves in finite depth water does not significantly affect the results

Tidal asymmetry in a prodominantly semidiurnal regieme estuary (case study - Logan River)

Proceedings of the Seventh International Conference on Hydroscience and Engineering, Philadelphia, PA, September 2006. http://hdl.handle.net/1860/732This study describes a field data collection and numerical modeling within the Logan River Estuary, located on the eastern coast of Australia. The study is aimed at investigating hydrodynamic behavior and resolving the tidal dynamic of the estuary under the action of environmental forces. The water level simulated by the model is analyzed for resolving the amplitude and phase of thirty-six tidal constituents. The result of this analysis is compared with measured tidal variations at seven locations along the estuary and current at one transect. The results are found to be consistent and the model is proved to be able to predict both tide and current accurately. Analysis of water level and current time histories shows strong asymmetry of tide along the Logan River Estuary. The results indicate that flood-currents are stronger than ebb currents, implying a flood dominant tidal regime, which potentially results in net coarse sediment transport into the estuary. The results also show a longer slack period at low water than that at high water and longer ebb current period than flood current period with a potential of net fine sediment transport seaward. Harmonic analysis of water level data indicates a mixed predominantly semi-diurnal tidal regime in the study area

Les fluoroquinolones (profil de tolérance et relation structure-activité)

MONTPELLIER-BU Pharmacie (341722105) / SudocSudocFranceF

Direct measurement of roughness of bed covered with gravel and ripples

In this study a series of experiments were conducted on different beds and under different flow conditions. The tests included a series of uni-directional near wall measurements of mean velocity. These tests were conducted in a channel covered with two types of roughness elements: i) bed covered with spherical aggregates with a diameter between 4 and 9.5mm ii) bed covered with triangular elements (an idealization of rippled beds) with a height of 13.6mm. The result shows that equivalent sand roughness associated with aggregate is of the order of the magnitude of the grain size. For rippled-like beds, the result of this study shows that this type of roughness can be adequately described with only one length scale (such as Nikuradse equivalent sand roughness) and that Dirling's empirical relation can best predict this length scale

Development of a device for direct measurement of bed shear stress induced by a wave spectrum

This paper describes a device (shear plate), which was developed for the direct measurement of shear stress applied to the bed by the action of gravity waves in a 50-meter long wave basin. This device is capable of resolving shear stress up to .05 N I m2 and measuring waves with a frequency of up to 5 Hz. This instrument in conjunction with a Laser Doppler Anemometer was later successfully used for the measurement of bed shear stress resulting from both monochromatic and spectrum of gravity waves. In this paper a full description of the device, some of the challenges encountered during its development, and some of the lessons learnt in the process of this exercise have been explained

Estuarine flood modelling using artificial neural networks

© 2014 IEEE. Prediction of water levels at estuaries poses a significant challenge for modelling of floods due to the influence of tidal effects. In this study, a two-stage forecasting system is proposed. In the first stage, the tidal portion of the available records is used to develop a tidal prediction system. The predictions of the first stage are used for flood modelling in the second. Experimental results suggest that the proposed flood modelling approach is advantageous for forecasting flood levels with more than 1 hour lead times

WSUD application audit at Gold Coast City

In recent years, Water Sensitive Urban Design (WSUD) has been strongly promoted in South East Queensland to mitigate quantity and quality issues in relation to stormwater. Gold Coast City Council has implemented WSUD devices widely for stormwater management for a number of years and is planning to continue this practice into the future. According to the planning policy of Gold Coast City Council, the adoption of WSUD practices is now mandatory for any new development within the city. As a result, Council is expected to be in possession of tens of millions of dollars of these assets in the future and will be responsible for their maintenance and long-term management. Any shortcoming in the implementation of best practice can potentially result in substantial liability for the Council in the future. However, there has been limited evaluation of WSUD systems in relation to their performance, long-term maintenance, and current knowledge gaps. It was considered that periodical audits of WSUD applications on the Gold Coast is vital to ensure that Council’s WSUD policies are continually improved to new learning and best practice is implemented and risk to Council is mitigated. After a series of stakeholder interviews within Council to understand current practical issues (weaknesses and strengths) in relation to the implementation of WSUD on the Gold Coast, a field audit comprising of condition assessment of eleven WSUD systems within four suburbs was undertaken to identify weaknesses and strengths in WSUD implementation on the Gold Coast. The outcomes of this study are presented in this paper