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The thesis investigated four south London catchments which drain northwards to the River Thames over superficial deposits which overlie clay in the North and chalk to the South. The catchments are densely urbanised ranging from 32.2 to 80.8 percent and range in area from 43.5 to 176.0 Km2. After evaluating several deterministic sewer and flood routing models it was decided to analyse 96 storm events by the unit hydrograph method. Testing of alternative identification techniques using objective error functions indicated that matrix inversion of response runoff and effective rainfall calculated by the loss rate curve was the most consistently accurate. Analysis of the unit hydrographs indicated that those with high peak discharges and short times to peak were caused by short duration, high intensity storms on a dry catchment, whereas unit hydrographs with a small peak discharge and a long time to peak were caused by long duration, low intensity storms on a wet catchment. The unit hydrographs from the four catchments showed no significant change through time. The mean unit hydrographs of the four catchments were not related to the degree of urbanisation, but to the physical characteristics of the catchments. The unit hydrographs were analysed and split tested using four different models. A quasi-linear, straight line approximation of the unit hydrograph proved to be the most consistently accurate. A subsidiary analysis compared the performance of seventeen linear conceptual models but was not followed up. A sensitivity analysis was conducted on the thesis's findings and quantified the significant effect of rainfall separation and profile on peak discharge and spill volume. The effect of substituting a straight line approximation of the unit hydrograph was examined and found to have a minor effect on peak discharge estimates but a more significant effect on spill volume.

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The subject of the thesis is the estimation and measurement of bed load discharge, i.e. the rate at which coarse sediment particles are transported in a flow of water, in particular in the River Tyne near Bywell. The first part of the thesis deals with the estimation of bed load discharge using empirical or theoretical formulae. A description of the collection of the necessary hydraulic and sediment data for the Bywell reach is followed by an account of the determination of the relationship between bed load discharge and river stage by several of the formulae available at present. Estimates of the average annual bed load discharge in the River Tyne at Dywell are given. In the second part of the thesis, concerning the direct measurement of bed load discharge, attempts to use a trap-type sampler from the Bywell cableway are described. An account of the development of an experimental laboratory channel for the investigation of an alternative technique, the detection of sediment movement by acoustic methods, is followed by a comparison of the observed and theoretical relationships between bed load discharge and the sound emitted by inter-particle collision of the moving sediment. An acoustic bed load detector for rivers is also described. Finally, a summary of concluSions, including recommendations for further research, is given.

The modular finite-difference groundwater flow model MODFLOW is one of the most widely used groundwater modelling programs, and is applicable to most types of flow problems in its field. However, its finite difference formulation decreases its ability to simulate accurately natural aquifer geometries. To enhance its capability in simulating such boundaries, a finite volume scheme has been developed for inclusion in MODFLOW. In this study, the two-dimensional formulation has been considered. Three discretisations of the two-dimensional diffusion equation, governing groundwater flow and for use with structured quadrilateral meshes, have been developed. The three methods rely on a cell-centred finite volume approach, but show distinct differences in the choice of: gradient approximation, head interpolations and control volume. A time implicit formulation has been used in each model. The sparse system of linear equations that result from the implicit formulation has been solved by using an iterative solver, based on the strongly implicit procedure. Five test examples have been undertaken to compare the performance of the newly developed methods against MODFLOW predictions and analytical results. The accuracy of the results obtained was found to depend on the spatial and temporal discretisations. One of the three developed methods proved its robustness, with regard to mesh non-orthogonality and skewness, and was called the GWFV method. In a second step of studies, a field case study was used to test the preferred model. A mesh generator using a structured quadrilateral grid was used to produce the finite volume mesh of the simulated area. The results of MODFLOW and the GWFV model simulations were compared against field observations. A discussion about the performance of the new developed model has been included and the model has been shown to perform well in comparison with MODFLOW.

Surface-water and groundwater are two resources both requiring careful management and protection. Computer modelling of both has long been used as an aid to their management. Historically they have been modelled separately, as their behaviour is represented by different mathematical equations. However, in reality, they are a linked resource each affects the other. DIVAST is a two-dimensional hydrodynamic and water quality numerical model developed for estuarine and coastal modelling. The original model enables the simulation of problems such as pollution and flooding in surface waters. In this study the existing model is extended to allow the modelling of groundwater as well as surface water in the same model. Chapters 1-5 introduce the problem, review some existing models, and then derive, discretise, and implement the equations for surface water and groundwater flow into the new model. Chapters 6-10 test the new model against analytical solutions, laboratory data, field data, and an existing groundwater model (MODFLOW). The outcome is a new version of the DIVAST model, known as DIVAST-SG (Depth Integrated Velocities And Solute Transport in Surface water and Groundwater). It simulates interactions between two-dimensional surface water and groundwater, in addition to the facilities of the original code. The equations are solved within one model, avoiding coupling problems. It is successfully tested against analytical solutions, laboratory studies and field data, and compared to an existing groundwater code, where it successfully models a gravel aquifer adjacent to tidal surface water. A framework is laid for continuing this work to produce a pseudo 3-D surface- water / groundwater code. In addition, novel techniques are pioneered in the laboratory, where open cell foam is used in a tidal flume to represent a porous aquifer adjacent to a river, and a highly detailed dataset of groundwater field data is compiled in the course of the work.

This study presents investigations on microbiological water quality numerical modelling. Emphases have been laid on the model development by implementing state-of-the-art technologies in terms of the new research branch in water science, established in 1980s - hydroinformatics. In the study, new mathematical equations for modelling bacterial re-suspension from bottom sediments and disappearance due to sediment deposition are established. Therefore, the bacterial re-suspension from bottom sediments is firstly modelled. The bacterial sedimentation equations presenting bacterial disappearance due to sediments settling process in natural waters is also introduced, which is independent from the well- known first order decay model. Based on the new equations, an integrated 1-D and 2-D hydroinformatics water quality simulation model has been developed, carrying out sediment transport associated bacteriological water quality modelling. The model therefore performs modelling work including hydrodynamic modelling, sediment transport modelling and bacterial decay modelling which is associated with the sediment transport processes. The new bacterial decay model encompasses the terms of bacterial first order decay, bacterial resuspension and the bacterial deposition. Object-oriented methodologies are employed in the integration of the sediment-associated multi-dimensional water quality model to encompass well-tested existing modules, by implementing Fortran 90 and Visual Basic 6.0 programming languages to deploy the advanced numerical schemes and provide a state-of-the-art GUI system. Validation and calibration of the integrated sediment-linked water quality model has been carried out in its application to the Bristol Channel and Severn Estuary by using vast volumes of data from in-situ field measurements including: diffuse faecal indicator sources of 29 riverine inputs point faecal indicators sources of 34 WwTW outfalls daily- recording hourly observed sunlight radiation data downstream real-time tidal water elevation boundary data upstream Severn River flowrate variations and the bathymetry data across the 1-D and 2-D domain. Satisfied calibration results were obtained and the model was successfully validated to estimate the enterococci concentration levels at beach bathing water compliance locations, thereby could now be applied to other estuarine environments.

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No description available.

For flow over a square-edged broad-crested weir the ratio of the measured discharge to the discharge predicted by simple one-dimensional theory may be expressed as an empirical coefficient. This coefficient has been found to have an almost constant value for a certain range of heads on any such weir. The thesis describes the development and verification of an analytical approach to account for the flow pattern in this range and, hence, for the factors limiting the range and for the value of the coefficient under these conditions. The hypothesis has as its basis the fact that a separation zone or roller is formed at the upstream edge, where the main flow is unable to follow the sharp right-angle corner but follows instead a curved path of finite radius. A control for the flow over the weir is thus established at a cross-section over this roller. To permit mathematical development, the simplifying assumption is made that within the roller the static head is constant while the main flow outside the roller is irrotational and hence amenable to treatment by potential flow theory. It is then possible to select tentative lines for the surface and for the outline of the roller and, by a relaxation technique, to obtain the distribution of values of the stream function. Velocities at the boundaries are then calculated; if these do not satisfy Bernoulli's equation, the boundaries are modified and the calculation is repeated. The digital computer facilitates the calculation and the plotting of streamlines. Downstream the surface profile rises and, with increasing crest length, waves and a hydraulic jump may be formed establishing a second control at the downstream end. These facts are related to accepted friction and wave theory. Experimental work confirming the analytical treatment is described. With weirs set in a laboratory flume, the flow pattern near the upstream edge was established using a pitot cylinder. In addition, surface profiles were observed as were velocity and pressure distributions along the crest, which permitted an assessment of energy degradation. Flow-head relationships were recorded and they are compared with the findings of earlier workers.