This thesis critically evaluates the reasons and extent to which Direct Action Self-Help (DASH) groups are, or can be, viable and an efficacious, efficient and effective means of managing and monitoring Flood and Coastal erosion Risk Management (FCRM) assets. FCRM DASH groups are found to be motivated by challenges of increasing flood risk and reduced public funding, alongside a sense of stewardship and community solidarity, catalysed by a few motivated individuals. The thesis develops a conceptual framework of the different dimensions, contextual aspects and motivations for DASH activity. Case studies show that channel maintenance work by DASH groups can be effective and efficient at reducing some aspects of local fluvial flood risk for lower order flood events. By contrast, maintenance of existing sea walls by DASH groups is less efficient because of the need for significant expenditure on materials and is only efficacious if the engineering is quality controlled; its longer term effectiveness is limited by sea level rise. Professional FCRM coordination and support of DASH activity is examined using a case study of an Environment Agency (EA) area coordinator and comparisons with alternative approaches. Support of DASH groups by FCRM professionals is essential to avoid unwise activity and to provide practical support, seed-corn funding and advice on the nature and extent to which DASH activity might be appropriate. The most effective form of DASH facilitation requires a quality and quantity of involvement that cannot readily be supplied by dispersed arrangements from a number of individuals. The thesis also proposes an approach for assessing and scoring the human dimensions of engineering assets. The dimensions of Sense of Security, Accessibility/Availability and Delight/Inspiration reflect insights from key thinkers from a wide range of disciplines. The framework is verified for the FCRM context and its practicality evaluated by trials in which DASH and other community groups assess human dimensions.

An investigation into the numerical and physical behaviour of a hybrid finite-volume finite-difference Boussinesq-type model, using a rotational surface roller approach in the surf-zone is presented. The relevant theory for the required development of a numerical model implementing this technique is outlined. The proposed method looks to achieve a more physically realistic description of the hydrodynamics by considering the rotational nature of the highly turbulent flow found during wave breaking. This involves a semi-analytical solution to the vorticity transport equation and provides a mechanism by which energy is dissipated. Resolving vorticity within the flow also allows vertical profiles of the horizontal velocity to be constructed, offering valuable detail that is otherwise unavailable when using equivalent irrotational Boussinesq-type models. By obtaining additional information about the structure of the flow, other quantities can be determined, such as the undertow, which has a key role in morphodynamic processes occurring in this region. These benefits are combined with a finite-volume finite-difference scheme, which yields improvements in stability and possesses inherent shock-capturing capabilities. The ability of the model to replicate laboratory observations is verified, and identified shortcomings are explained in the context of the numerical procedure and the assumptions made during the derivation of the governing equations. Although the weak nonlinearity of the Boussinesq-type equations means the shoaling characteristics of the model do not accurately reflect those found experimentally, the adopted formulation of the finite-volume scheme is shown to prevent the inclusion of the necessary higher-order derivatives which exist in a fully-nonlinear formulation. In order to establish a realistic dissipation mechanism, it is vital that the extent of any misleading numerical artefacts are recognised and their effects alleviated. This study explores a range of physical attributes predicted by the present model and discusses the numerical features of the scheme, evaluating how these influence the results.

The accurate prediction of wave overtopping is one of the most important aspects in the design of coastal defence structures. This can be achieved by using three different approaches: by physical modelling using laboratory tests, by empirical formulae available in literature derived from physical modelling and field tests, or by numerical simulation of the hydraulic response of the structure. All of these prediction methods are subject to a certain level of uncertainty. One source of this is the requirement of a defined free surface elevation and velocity time series seaward boundary condition in any model. Often, these are not available but the modeller is instead provided with an incident energy density spectrum. A time series will then be reconstructed from this spectrum to be used as boundary conditions. Since the energy density spectrum provides only information on the amplitude of the components, it is usually assumed that the phases of these components are randomly distributed. To create the randomly generated phases, an initial seed value is required to generate a population of uniformly distributed random phases. By varying this value for each simulation a different time series will be produced. The overall objective of this research is to quantify the uncertainty in the prediction of overtopping due to this process. This research involved carrying out two sets of laboratory experiments. Firstly, those carried out in the 2D wave flume at HR Wallingford, which provided a reference case for the validation of a numerical model, as well as a measured incident wave spectra for the generation of the population of reconstructed offshore boundary time series. The second set of experiments was carried out in the smaller 2D flume at the University of Nottingham to investigate the effect of random seeding to generate the time series at the wave paddle on the resulting overtopping parameters. This was also carried out to allow a comparison in the variability between the physical and numerical results. It was found in the work, that when a measured free surface elevation is used as the input, good agreement between the numerical solver prediction and the overtopping measurements was observed. Subsequently, when a Monte Carlo approach was used to generate the population of reconstructed offshore boundary time series from the measured incident spectra the statistical analysis of the results showed that the variability was higher for the small numbers of overtopping waves and decreases as overtopping becomes more frequent. To allow for more generalised conclusions on the uncertainty, further numerical tests were then carried out with synthetic spectra allowing different hydraulic and structural parameters to be considered. These showed good agreement with the findings of the initial statistical analysis. Finally, the results from the physical model tests carried out at the University of Nottingham were analysed. The influence of laboratory effects were studied and analysis was carried out to establish the magnitude and sources of variability in these results. As with the numerical results, the characteristics of the distribution of the predicted overtopping parameters were also studied.

Climate change, population growth, and water resources crossing political boundaries are the main issues threating water allocation for agricultural, industrial and domestic uses in developing countries. Integrated water resources management developed in a sustainable manner is essential to allow future generations to meet their water needs. A lack of data in developing countries is the biggest problem that can hinder developing necessary understandings. The Tigris river basin is a prime example, not only because it is located in a developing country, but also due to its long history of armed conflicts and breakdown of law and care. Unstable situation makes data collection difficult, available data poor in quality and the measuring tools and methods rudimental. The insufficient data lead to the impact of the climate change on water resources to be not conclusively detrained. This study shows the climate change impacts through investigate the evapotranspiration (ET) changes over the years. Five potential evapotranspiration models have been studied and classified according to the complexity in terms of the number of variables. Choosing the most suitable ET model helped to fill and reconstruct gaps in historical data sets. The statistical downscaling model SDSM was used to predict the evapotranspiration changes for the next 100 years. Google Earth and 3DRoutBuilder helped to produce an entire river profile with a simple, good quality representation of river networks. That aid the run of the hydrodynamic model (ISIS -1D) which has been utilised to produce water levels and water flow information to establish a robust river losses and water balance assessment for a river. Planning of alternative water resources schemes on river basins located in Arid-Semi Arid region needs an assessment of the hydrologic/hydraulic behaviours of that river. In view of this, the thesis further explores the sustainability of water quantities of rivers based on generated climate scenarios and population increases.

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This research work aims at using a fully-coupled hydro-morphodynamical numerical solver to study the beachface evolution at the storm time-scale. The proposed model originates from that of Briganti et al. (2012a), who considered a system comprising the Nonlinear Shallow Water Equations and the Exner one (bed-load only). Suspended load, bed diffusion and infiltration are now included, following Zhu (2012) and Dodd et al. (2008) approaches. The original version of the numerical scheme (TVD-MCC) is modified to deal with the aforementioned additional physics, while the infiltration computation is implemented at the end of each time step (see Dodd et al., 2008). A new treatment for the wet / dry front is adopted, following the previous work of Hubbard & Dodd (2002). About model validation, enhanced results are obtained in both the fluvial dune and the dam break tests with respect to those of Briganti et al. (2012a). In the uniform bore test with bed-load the results confirm those of the previous version (see Zhu et al., 2012), while in the case with combined load they show an overall good agreement with the reference solution, even though the maximum run-up is underestimated. Single swash on fixed slope experiments are reproduced as well. In the impermeable case the results are improved on those of Briganti et al. (2011), while in the permeable one the overall performance is thought to be reasonable (better the uprush than the backwash). Although the maximum predicted inundations are smaller than measured, hydrodynamic results compare quite well with field data for real single swash events, thus confirming that one-dimensional, depth-averaged description of the swash is reasonable. The final computed bed changes show the correct order of magnitude but are generally underestimated and the predicted pattern is not always observed in the data. The sensitivity analyses indicate that this discrepancy is probably due to the initial (unknown) distributions of pre-suspended sediment concentration and velocity. The morphodynamic evolution of two beaches at the storm time-scale is studied. In the bed-load test, results compare very well with the reference ones from Dodd et al. (2008) and Sriariyawat (2009) and, in general, the sensitivity analyses for the permeable beach case confirm previous findings. In the combined load test, the Meyer-Peter and Müller formula is applied excluding the threshold for sediment movement. This assumption is not expected to have a significant impact on the morphodynamic evolution, in the limits of the chosen parameters and settings. Increased efficiency in the entrainment rate for suspended load is found to promote onshore transport, extending Pritchard & Hogg (2005) observation for single swash events to the case of multiple ones. Variations in the incoming wave period and height yield different final bed change profiles from the default one (three long-shore bars and generally deposition seaward and erosion landward), showing differences in the number of formed bars and in the morphodynamic pattern, with sometimes accretion in the upper beach. Beside this, new seaward boundary conditions (REBCs) are derived. They do not alter flow and bed level patterns generated by nonlinear standing waves on mobile bed, do converge to the hydrodynamic conditions on virtually-fixed bed and perform reasonably well in the demanding morphodynamic bore test.

Tidal stream power generation offers the prospect of predictable, low-CO2 power at a number of locations around the UK and the world. Previous assessments of tidal energy resources have taken the form of desk studies based on simplified navigational data. Where numerical model data has been used it has been at too low a resolution to capture high velocity tidal flows constrained by coastal topography. Analytical solutions for maximum energy extraction in simple tidal channels have been produced, but they have not been extended to more complex open-boundary cases such as flow around headlands and islands. There is therefore a role for site-specific numerical modelling, which when validated, offers the twin advantages of a high-resolution picture of the resource and allowing simulation of momentum extraction within the model to take place. In order to parameterize the sub-grid-scale momentum extraction in such models, a new analytical model of the velocity reduction in a large array of tidal turbines has been derived. The model extends previous models of large wind turbine arrays and uses analogies with flow through submerged vegetation. It provides an equivalent added drag coefficient suitable for use in a 2-D coastal numerical model. A numerical model of the flows in the region of the Portland Bill headland has been produced, forced by tidal elevations at the free boundary. A site selection exercise was carried out for the Portland Bill location and an area of around 12 km2 was identified as having a high potential for development using mean cubed speed found through tidal analysis of model results without energy extraction. A large tidal stream generator array has also been simulated within the Portland Bill model—linked to the new model for momentum extraction—and was found to have a significant effect on the tidal parameters in the locality. This was the first time that a large tidal array has been simulated in a realistic coastal domain of large extent, with a parameterization that takes into account the interaction of the turbines with the rough-wall flow in the natural state. Results predict that there is a region downstream of the array extending approximately 5–10 km around the simulated tidal stream turbine array in which the tidal stream ellipse major axis is reduced by at least 5%. In the area of momentum extraction the principal semi-diurnal tidal stream ellipse major axis length was reduced by 10–15%.

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