Dissertations / Theses on the topic 'Inundation'

In this thesis, detailed tsunami numerical modeling study was applied to the selected case studies, Fethiye town (Turkey) and Kiparissia-Zakintos-Pylos (Greece) in Mediterranean, using rupture-specific tsunami sources which can generate tsunamis in Mediterranean. As a first step of the study, the general database of Fethiye and Kiparissia-Zakintos-Pylos were integrated to GIS-based environment to organize, analyze and display reliable data from different sources. Secondly, for each earthquake scenario, the tsunami propagation and coastal amplifications were computed by TUNAMI N3 to evaluate the coastal amplifications of tsunamis and understand the tsunami propagation for the cases. As the final step, a study of inundation areas of probable tsunamis in these regions was performed. Available results were used to understand the effects of tsunamis and assist in developing mitigation strategies. Methods and results were presented and discussed.

Sediment transport and morphological change can play an important role during extreme coastal flood events. In this thesis, a set of 2-D shallow water-sediment equations is derived that incorporate suspended sediment, bedload transport and bed morphological evolution. A balanced stage-discharge hyperbolic formulation is adopted, which is suitable for complex shallow flows such as large-scale inundation over natural terrain. The 2-D shallow water-sediment equations are solved using a second-order Godunov-type approximate Riemann solver on dynamically adaptive quad tree grids. The numerical model is capable of simulating large-scale flood inundation over complex terrain. A number of test cases have been presented to validate the numerical model. The thesis also presents results from wave overtopping experiments of a scale model of the Anchorsholme seawall, carried out at HR Wallingford. The measurements of water surface elevation time histories from focused and irregular wave tests should be useful for validating numerical models of wave overtopping. The 2D shallow water model has also been applied to simulate the coastal flood inundation of Walcott, Norfolk. Considerable care has been taken to include building configurations. The results reproduce the pattern of flooding experienced at Walcott in November 2007, and demonstrate the importance of the street layout in channelling flood water. A Lagrangian particle tracking model is also presented for predicting the near bed saltation of sediment particles. In order to achieve higher order of accuracy, a fourthorder Runge-Kutta scheme is used for time-integrating the equations of motion of a spherical particle. Particle saltation over a flat bed and over a uniform bed comprised of hemispherical particles are simulated in unidirectional flow. The nonlinear dynamics of the particle saltation is investigated, and both regular and chaotic motions are observed. The Lagrangian particle saltation model has also been extended to simulate sediment particle transport in tidal flow.

This thesis is submitted alongside the film Forecast (2015) to be a submission for the PhD project Cantre?r Gwaelod and Tales of Inundation. The project aims in its entirety to propose film as a mode of enquiry regarding ways in which the dangers of climate change, specifically anthropogenic climate change, can be addressed in a documentary film. Using the possible allegorical power of the Welsh flood myth of Cantre?r Gwaelod, the original aim of the project was to create a documentary film which used this myth as a way to illustrate the effects of a changing climate. During the research, however, it became apparent that myth as a concept presented several points of interest which overall problematised its use in this way. Myth itself could be seen to be present in mass communication because some simplification of complex issues needs to take place in order to make this type of communication possible. Furthermore, it also became clear that the issue of climate change had to some extent been mythologised through a similar process of simplification. This project looks closely at the ways in which this tendency towards mythology in communication, especially regarding complex issues such as climate change, might, in fact hinder the communication of themes and ideas and damage the efficacy as a result. It therefore became obvious that the purpose of this project was to develop a methodology which attempted to communicate through a documentary film in a way that eschewed mythology as much as 2 possible. This written thesis looks at the ways in which this was achieved, both theoretically and practically and details extant work that serves to illustrate this.

Flood inundation phenomena typically occur over reach lengths of 5- 30 km and incorporate a number of complex flow mechanisms. These include a momentum transfer between the main channel and floodplain and turbulent mixing caused by the delivery of water to the floodplain from the channela nd its subsequenrte turn. However, currently available one dimensional schemes applicable at scales appropriate to floodplain inundation processes cannot effectively simulate such processes. This is due to both an incomplete description of the flow physics and a failure to treat floodplain areas in realistic fashion. More complex two and three dimensional models, which have these capabilities, have only been applied over very short reach lengths (c. 0.5 -2 km) and rarely to compound meandering channels. This thesis reports on the further development of a generalized two dimensional, finite element code (RMA-2) to meet this research need. This is achieved via a series of modifications to the numerical model and to the physical representation by finite elements that enable river channel/floodplain flow at the long reach scale to be effectively simulated. Evaluationo f the enhancedR MA-2 schemef ollows a three stages trategy. Firstly, the assumptions underlying the scheme are examined to identify possible inconsistencies. Secondly, tests are undertaken to assess whether the specified physical model has been correctly transferred into computer code. This is achieved via sensitivity analysis, examination of numerical stability issues and investigation of model response to abnormal parameterization. Thirdly, model predictions of flow field information are compared to observed field data in the context of an application of the enhanced model to an 11 km reach of the River Culm, Devon, UK. Results from this evaluation process indicate that the enhanced RMA-2 model is capable of simulating main channel/floodplain momentum transfer and the two dimensionale ffects associatedw ith compoundm eanderingc hannelsa t this scale. Model simulations compare favourably to field data, both for specific cross sections and over the entire mesh. Finally, extension of this core modelling capability is begun via the development of two model application scenarios. These demonstrate the likely utility of the enhanceds chemef or the assessmenotf flood risk and the investigationo f sediment depositionp rocessesin floodplain systems.

An important problem encountered by foundation engineers involves partially saturated soils which possess considerable in-situ dry strength that is largely lost when the soils become wetted. Foundation design in such soils is difficult at best. In many cases, deep foundations may be required to transmit foundation loads to suitable bearing strata below the 'collapsible' soil deposit. This research has studied the behaviour and performance of stone columns confined and not confined by geofabrics and rigid piles, as deep foundations, in collapsible soil subjected to inundation. Laboratory tests were carried out, under controlled conditions of sand density and surcharge pressure, using six different types of foundation supports (a sand column, sand columns confined by T700, T1000, T1500 or T2000 geofabrics and a rigid pile). Each type of foundation was considered in three different lengths 250 mm, 300 mm and 410 mm. This work consisted of installing and loading 'model' foundations into a stress controlled pot containing a collapsible soil and allowing a slow rise of the water level inside it. The tests were designed to investigate the efficiency of these types of foundation supports on the improvement of the carrying capacity and on the reduction of settlement of the ground. The reduction in vertical compression of the 'piles' was also studied analytically using an analytical approach adopted and developed from models applied to soft soils. The experimental results are compared with analytical predictions. The comparisons show that the reduction in vertical compression of the 'pile' is governed by its stiffness and its length. These variables are of prime importance in the general performance of the 'pile'.

Recent evaluations of 2D models have analysed uncertainty in data inputs into flood models, but have treated the model code as a black box. In this work, the influence of the numerical representation of the model on the results is evaluated. The purpose is not only to understand the significance of the physical scheme in the model on results, but also the importance of this in respect to other known sources of uncertainty, in particular boundary conditions, calibrated parameters such as Manning’s friction values, DEM accuracy and other more subjective forms of uncertainty associated with the choices used by modellers in constructing models, such as building representation. To further explore the impact that the level of physical representation has on model output, models were also analysed using risk and exposure based measures. The methods included vulnerability weighted measures and the use of damage curves from the Multi Coloured Manual. A series of Monte Carlo tests were undertaken for a range of parameters over 3 test cases using the LISFLOOD-FP code. The LISFLOOD-FP code was chosen as it has several formulations for solving 2D floodplain flow within its framework, each with different level of physical representation. The test cases included two urban events, a culvert overtopping event in Glasgow and canal embankment failure Coventry, and a river overtopping in Mexborough, Yorkshire a rural urban domain. The test cases provided a wider range of hydraulic conditions and are reflected events typically assessed with inundation models to ensure the effect of model bias was removed from the results. The results for the test cases indicated that the choice of physical representation was the most critical in affecting model results, particularly for the urban test case. However, the interaction between factors and parameters also indicated that for certain scenarios, this becomes less critical to model results. The use of risk based methods also identified areas of variations between parameters sets and numerical schemes that are not identified with traditional model evaluation techniques. Recent evaluations of 2D models have analysed uncertainty in data inputs into flood models, but have treated the model code as a black box. In this work, the influence of the numerical representation of the model on the results is evaluated. The purpose is not only to understand the significance of the physical scheme in the model on results, but also the importance of this in respect to other known sources of uncertainty, in particular boundary conditions, calibrated parameters such as Manning’s friction values, DEM accuracy and other more subjective forms of uncertainty associated with the choices used by modellers in constructing models, such as building representation. To further explore the impact that the level of physical representation has on model output, models were also analysed using risk and exposure based measures. The methods included vulnerability weighted measures and the use of damage curves from the Multi Coloured Manual. A series of Monte Carlo tests were undertaken for a range of parameters over 3 test cases using the LISFLOOD-FP code. The LISFLOOD-FP code was chosen as it has several formulations for solving 2D floodplain flow within its framework, each with different level of physical representation. The test cases included two urban events, a culvert overtopping event in Glasgow and canal embankment failure Coventry, and a river overtopping in Mexborough, Yorkshire a rural urban domain. The test cases provided a wider range of hydraulic conditions and are reflected events typically assessed with inundation models to ensure the effect of model bias was removed from the results. The results for the test cases indicated that the choice of physical representation was the most critical in affecting model results, particularly for the urban test case. However, the interaction between factors and parameters also indicated that for certain scenarios, this becomes less critical to model results. The use of risk based methods also identified areas of variations between parameters sets and numerical schemes that are not identified with traditional model evaluation techniques.

This thesis analyzed the new parameter hydrodynamic demand representing the damage of tsunami waves on structures and coastlines,maximum positive amplitudes and current velocities occurred during tsunami inundation by using the numerical model TUNAMI-N2. Regular shaped basins were used with two different bottom slopes in analyses in order to understand the behaviour of tsunami wave and investigate the change of important tsunami parameters along different slopes during tsunami inundation. In application, different initial conditions were used for wave profiles such as solitary wave, leading elevation single sinusoidal wave and leading depression sinusoidal wave. Three different initial wave amplitudes were used in order to test the change of distribution of the hydrodynamic demand. The numerical results were compared and discussed with each other and with the results of existing analytical and experimental studies.

After the Boxing Day 2004 Sumatran Tsunami, a review of tsunami hazard and risk for New Zealand identified Gisborne as the urban area with the greatest risk. Gisborne could experience gt;500 fatalities and extensive damage to infrastructure during a severe tsunami. The severity of a tsunami is likely to be low for distance sources given the effectiveness of the Pacific Tsunami Warning System. However, there is a substantial risk from local sources, as no local warning system of any kind exists. Prompt evacuation is probably the most cost-effective tsunami mitigation strategy available for New Zealand coastal locations, including Gisborne. This requires both knowledge of the extent of tsunami inundation, and sufficient warning of the tsunami arrival. Hence, there are two main objectives for this investigation: 1. Determine the likely extent of tsunami inundation for Gisborne City and surrounding populated coastal locations in Poverty Bay, using a combination of hydrodynamic tsunami modelling and GIS. The modelling will simulate historical events, particularly the largest historical tsunami, the May 1947 local tsunami. Modelling will consider potential events based on the Maximum Credible Earthquake for local sources associated with the Hikurangi Deformation Front. 2. Create inundation maps of Poverty Bay that can be used for future town planning and emergency plans.

Key uncertainties within inundation modelling of storm tide overflow were investigated for two regions. A northern Bay of Bengal LISFLOOD-FP inundation model was developed from freely available data sources, and forced with a storm surge model (IIDT) hind-cast of the 2007 cyclone Sidr flood event because no quality water-level records exist. Validation showed inundation prediction accuracy, with a Root Mean Squared Error (RMSE) on predicted water-level of...., 2 rn, which was similar in magnitude to the forcing water-level uncertainty. Indeed, when observed natural variability within five key cyclone parameters was propagated through the IID-T storm surge model, extreme water-level uncertainty was found to be very high in the Bay of Bengal, and should be considered in future work (and flood risk managers). Future flood hazard mapping uncertainty is much less in the data rich UK; however, when some key uncertainties were propagated through a North Somerset LISFLOOD•FP inundation model of the 1981 historic flood, storm tide spatial variability was found to significantly affect flood risk estimates, second only to sea level rise. A new method for prescribing the still peak water-level along a coastline was developed (Method C), which characteristics the spatial variability using a relatively short record of modelled extreme water-level events, relative to a tide gauge. Good agreement (RMSE 36 cm) was found between Method C predicted water-levels and tide gauge observations for two historic flood events in East Anglia (1953 and 2007). Furthermore, remotely sensed storm tide observations along the North Somerset coast indicated the accuracy of Method C between tide gauge observations; however, fine-scale wave and bathymetry effects need to be resolved for accurate coastal flood risk estimates in the UK. Indeed, the quantification of uncertainty, and the characterisation of natural variability, is necessary for a robust flood risk prediction.

High-resolution data obtained from airborne remote sensing are increasing opportunities for representation of small-scale structural elements (e. g. walls, buildings) in complex floodplain systems using two-dimensional (2D) models of flood inundation. At the same time, 2D inundation models have been developed and shown to provide good predictions of flood inundation extent, with respect to both full solution of the depth-averaged Navier-Stokes equations and simplified diffusion wave models. However, these models have yet to be applied extensively to urban areas. This study applies a 2D raster-based diffusion wave model, either loosely-coupled or tightly-coupled to a ID river flow model, to determine patterns of fluvial flood inundation in urban areas using high-resolution topographic data. The aim of this study is to explore the interaction between spatial resolution and small-scale flow routing process, through model validation and verification. The model assumes that the prime source of the flood is fluvial: pluvial floods and floods associated with urban drainage systems are not addressed. The topographic data are based upon airborne laser altimetry (LiDAR) obtained for the City of York, U.K. Validation data were available in the form of inundation patterns obtained using aerial photography at a point on the failing limb of the flood event. Inflow data is provided either by a loosely-coupled or a tightly-coupled ID river flow model. The model was used to simulate a major flood event which occurred in the year 2000 in the City of York on the River Ouse at 4 different sites. Applications of the basic model showed that even relatively small changes in model resolution have considerable effects on the predicted inundation extent and timing of flood inundation. Timing sensitivity would be expected given the relatively poor representation of inertial processes in a diffusion wave model. Compared with previous work, sensitivity to inundation extent is more surprising and is associated with three connected effects: (i) the smoothing effect of mesh coarsening upon input topographical data; (ii) poorer representation of both cell blockage and surface routing processes as the mesh is coarsened, where the flow routing is especially complex; and (iii) the effects of (i) and (ii) upon water levels and velocities which in turn determine which parts of the floodplain the flow can actually travel to. The combined effects of wetting and roughness parameters can compensate in part for a coarser mesh resolution. However, the coarser the resolution, the poorer the ability to control the inundation process as these parameters not only affect the speed but also the direction of wetting. Thus, high resolution data will need to be coupled to more sophisticated representation of the inundation process in order to obtain effective predictions of flood inundation extent. A sub grid scale wetting and drying correction approach was developed and tested for use with 2D diffusion wave models of urban flood inundation. The method recognises explicitly that representations of sub grid scale topography using roughness parameters ill provide an inadequate representation of the effects of structural elements on the floodplain (e. g. buildings, walls) as such elements not only act as momentum sinks, but also have mass blockage effects. The latter may dominate, especially in structurally complex urban areas. The approach developed uses high resolution topographic data to develop explicit parameterization of sub grid scale topographic variability to represent both the volume of a grid cell that can be occupied by the flow and the effect of that variability upon the timing and direction of the lateral fluxes. This approach is found to give significantly better prediction of fluvial flood inundation in urban areas as compared with traditional calibration of sub grid-scale effects using Manning's n. In particular, it simultaneously reduces the need to use exceptionally high values of n to represent the effects of using coarser meshes, whilst simultaneously increasing the sensitivity of model predictions to variation in n. Finally, the model was coupled (tightly) to a one-dimensional solution of the Navier-Stokes equations. This showed that significantly better representation of urban inundation could be achieved in a tightly-coupled formulation as a result of better representation of boundary condition effects.

Tsunamis, as the catastrophic disasters, can cause loss of live and property when they come to the shores. Preparation of emergency plans is essential to reduce the damage. Consequently, any initiative in tsunami modeling and inundation mapping is of vital importance for progressing safety surveillance and maintenance. In an effort to achieve a thorough analysis of effect of tsunami, it is critical to estimate the geographical extent of possibly affected area and to predict tsunami impacts. The inundation mapping system also must serve to manage the simulation data in a scalable environment to reach end-users in the time of event. For this purpose, in this study, the generation of a Web based Geographic Information System (GIS) to serve inundation maps through web. The research methodology consists of four main stages: (i) simulating tsunamis based on six different scenarios (ii) processing simulation data through a GIS application
(iii) development of web interfaces and implementation of the developed model for Web-GIS application
(iv) verification of the created model for Marmara Sea Region. The proposed system is expected to be an efficient tool for improving inundation mapping efforts for expected tsunamis in Turkey.

Government flooding policy across Europe, and in the UK, has switched from flood defence to flood risk management. The approach requires the evaluation of the consequences of all possible asset failures over a range of flood probabilities. For a typical flood system this necessitates the simulation of thousands of inundation permutations. As a consequence, the speed of simulation is a significant factor in the practical implementation of this approach. This thesis reports on the development and testing of a Rapid Flood Inundation Model (RFIM) designed to satisfy this requirement. The model consists of a precalculation part, and a subsequent rapid flood inundation prediction. Three variations of the rapid inundation routine are presented. The algorithms differ in the way in which the flood depth on the communication links between the cells is calculated. The latter version also permits a spatially limited estimation of flow velocities. The RFIM was applied to the Greenwich and Thamesmead embayments on the River Thames in London. The main objectives of the RFIM testing were: to evaluate the predictive capabilities of the simple volume spreading method used. In order to undertake the task a Monte Carlo analysis was performed and the flood extent maps were compared to predictions produced by the two-dimensional hydrodynamic model, TUFLOW. The overall performance of the model was found to be acceptable, although some inaccuracies in the predictions, as a result of the oversimplification of the hydraulics, were observed. These were discussed and recommendations were given to improve model behaviour. The computational speeds were found to be acceptable and within the required limits. It is therefore suggested that the proposed Rapid Flood Inundation Model can be used for flood predictions in urban areas for the purpose of flood risk management.

Flood disasters are a major cause of fatalities and economic losses, and several studies indicate that global flood risk is currently increasing. In order to reduce and mitigate the impact of river flood disasters, the current trend is to integrate existing structural defences with non structural measures. This calls for a wider application of advanced hydraulic models for flood hazard and risk mapping, engineering design, and flood forecasting systems. Within this framework, two different hydraulic models for large scale analysis of flood events have been developed. The two models, named CA2D and IFD-GGA, adopt an integrated approach based on the diffusive shallow water equations and a simplified finite volume scheme. The models are also designed for massive code parallelization, which has a key importance in reducing run times in large scale and high-detail applications. The two models were first applied to several numerical cases, to test the reliability and accuracy of different model versions. Then, the most effective versions were applied to different real flood events and flood scenarios. The IFD-GGA model showed serious problems that prevented further applications. On the contrary, the CA2D model proved to be fast and robust, and able to reproduce 1D and 2D flow processes in terms of water depth and velocity. In most applications the accuracy of model results was good and adequate to large scale analysis. Where complex flow processes occurred local errors were observed, due to the model approximations. However, they did not compromise the correct representation of overall flow processes. In conclusion, the CA model can be a valuable tool for the simulation of a wide range of flood event types, including lowland and flash flood events.

Flood disasters are a major cause of fatalities and economic losses, and several studies indicate that global flood risk is currently increasing. In order to reduce and mitigate the impact of river flood disasters, the current trend is to integrate existing structural defences with non structural measures. This calls for a wider application of advanced hydraulic models for flood hazard and risk mapping, engineering design, and flood forecasting systems. Within this framework, two different hydraulic models for large scale analysis of flood events have been developed. The two models, named CA2D and IFD-GGA, adopt an integrated approach based on the diffusive shallow water equations and a simplified finite volume scheme. The models are also designed for massive code parallelization, which has a key importance in reducing run times in large scale and high-detail applications. The two models were first applied to several numerical cases, to test the reliability and accuracy of different model versions. Then, the most effective versions were applied to different real flood events and flood scenarios. The IFD-GGA model showed serious problems that prevented further applications. On the contrary, the CA2D model proved to be fast and robust, and able to reproduce 1D and 2D flow processes in terms of water depth and velocity. In most applications the accuracy of model results was good and adequate to large scale analysis. Where complex flow processes occurred local errors were observed, due to the model approximations. However, they did not compromise the correct representation of overall flow processes. In conclusion, the CA model can be a valuable tool for the simulation of a wide range of flood event types, including lowland and flash flood events.

The Doñana wetlands, in Southwest Spain, undergo yearly cycles of inundation in fall and drying out during the spring season. As any wetland ecosystem, Doñana depends critically on its water resources. Important monitoring and modeling efforts have been made since the 1990's in order to assess the ecosystem health, partially restore Doñana¿s natural hydrologic scheme and design climate change adaptation strategies for ensuring its sustainability. The present research work inscribes within those efforts. Satellite images of Doñana marshes were acquired between 2006 and 2010, in order to obtain regional, synoptic observations of the inundation evolution, with the final aim to further current knowledge on the wetland's hydrology and to calibrate the existing two-dimensional hydraulic model of the marshes. The images were acquired by the C-band radar sensor ASAR, on board the Envisat satellite. ASAR's all-weather observation capability was particularly suitable to observe the flooding process, since this is associated to overcast weather. The images were ordered at seven different incidence angles in order to increase the observation frequency, and most of them in HH and VV polarizations. A detailed observation of the wetland filling up was achieved during the 2006-2007 hydrological cycle. Backscattering temporal signatures of the main land cover types in Doñana were derived for the different incidence angles and polarizations. The signatures were analyzed with the aid of ground-truth data in order to identify the effect of the flooding on the backscattering coefficients. Conclusions on the feasibility to discriminate emerged versus flooded land were drawn for the different incidence angles, land cover types and phenological stages: Intermediate incidence angles (ASAR IS3 and IS4) came up as the most appropriate single swaths to discriminate open water surface from smooth bare soil in the marshland deepest areas. Flood mapping in pasture lands, the most elevated regions, is feasible at steep to mid incidence angles (ASAR IS1 to IS4). In the medium elevation zones, colonized by large helophytes, shallow incidence angles (ASAR IS6 and IS7) enable more accurate flood delineation during the vegetation growing phase up to approximately mid-April, when the penetration capacity at these swaths might become insufficient. Due to the complex casuistic of the Doñana covers' backscattering, flood mapping from single ASAR acquisitions often resulted unfeasible. Flood mapping was then tackled by the synergistic use of the ASAR scenes with the Doñana¿s digital terrain model and vegetation map. The use of irregular filtering neighborhoods adapted to the topography drastically improved the ASAR image filtering, since natural edges tend to follow terrain contours. Clustering and classification algorithms were design to operate on individual sub-basins, as the pixels elevation is more accurately related to the cover classes within them. Vegetation and elevation maps plus knowledge of Doñana's backscattering characteristics from preceding studies were initially used to select seed pixels with high confidence on their class membership. Next, a region growing algorithm extends the seed regions with new pixels based on their planimmetric adjacency and backscattering distance to the seeds. Frequent flood mapping from the ASAR scenes enabled the identification of several events for the calibration of the marshes hydraulic model. This research work also revealed other target information enclosed in the radar backscattering, such as the helophyte vegetation developmental degree or the potential to discriminate among plant communities. Learnings from this research work are expected to be applied and furthered with upcoming data from the C-band Sentinel-1 constellation and Radarsat-2 satellite, the L-band ALOS-2/PALSAR-2 system and the X-band future Spanish mission PAZ.
Las marismas de Doñana, situadas en el suroeste de la Península Ibérica, experimentan ciclos anuales de inundación en otoño y secado en primavera. Como en cualquier humedal, la sostenibilidad de Doñana depende críticamente de sus recursos de agua. Desde la década de los noventa se han realizado importantes esfuerzos de monitorización y modelación para evaluar la salud del ecosistema marismeño y restaurar en lo posible su régimen hidrológico natural, para prever riesgos derivados de las actividades socio-económicas próximas y del cambio climático, y para diseñar estrategias de adaptación que garanticen su sostenibilidad La presente tesis doctoral forma parte de estos esfuerzos. Entre los años 2006 y 2010 se encargó la adquisición expresa de numerosas imágenes satelitales de Doñana con el objeto de obtener observaciones regionales y sinópticas de la evolución de la superficie inundada en el humedal. Con estas observaciones se pretendía avanzar en el conocimiento de la hidrodinámica de las marismas y calibrar el modelo hidráulico bidimensional de las mismas. Lograr una frecuencia de observación elevada durante el llenado de las marismas fue un requisito de especial interés, pues es durante este período cuando la lluvia es más abundante y los procesos hidrodinámicos suceden a mayor velocidad. Las imágenes fueron adquiridas por el sensor radar en banda C ASAR, a bordo del satélite Envisat de la Agencia Espacial Europea. La capacidad de la banda C para atravesar la cobertura nubosa resultó particularmente apropiada para monitorizar con detalle el proceso de llenado, ya que éste se halla asociado a la presencia de nubes. Las imágenes ASAR se solicitaron en siete ángulos de incidencia diferentes para incrementar la frecuencia de observación y la mayoría de ellas fueron adquiridas con la configuración de polarizaciones HH/VV. Durante el año hidrológico 2006-2007 se consiguió una monitorización detallada del proceso de llenado. Para este ciclo se elaboraron signaturas temporales de los principales tipos de cubiertas en Doñana, en los distintos ángulos de incidencia y polarizaciones disponibles. Las signaturas se analizaron con la ayuda de datos de verdad-terreno para identificar el efecto de la inundación sobre el coeficiente de retrodispersión y se extrajeron conclusiones sobre la posibilidad de discriminar superficies emergidas e inundadas en función del ángulo de incidencia, tipo de cobertura vegetal y fase fenológica: ángulos de incidencia intermedios, como los IS3 e IS4 de ASAR, resultaron ser los más apropiados para discriminar en una única imagen superficies de agua libre. La cartografía de inundación en los paciles, las regiones más elevadas, es factible usando ángulos reducidos y medios (entre IS1 e IS4 de ASAR). En las zonas de elevación intermedia, colonizadas por grandes helófitos, los ángulos de incidencia elevados (IS6 e IS7 de ASAR) permiten una delimitación de la inundación más precisa durante el desarrollo de la vegetación hasta aproximadamente mediados de abril, cuando la capacidad de penetración de estos ángulos puede resultar insuficiente. Dada la compleja casuística de la retrodispersión de las cubiertas de Doñana, a menudo resultó inviable delinear la inundación en toda la marisma a partir de una única adquisición de ASAR. La cartografía de inundación se abordó entonces mediante el uso sinérgico de los datos ASAR con el modelo digital del terreno y el mapa de vegetación de Doñana. El uso de entornos de procesado irregulares adaptados a la topografía mejoró drásticamente el filtrado de las imágenes, ya que los bordes naturales tienden a seguir las curvas de nivel del terreno. A continuación se diseñaron algoritmos de agrupación y clasificación de píxeles que utilizan los datos ASAR junto con la cota del terreno y el mapa de vegetación, y que se aplican independientemente en las distintas subcuencas de Doñana, porque dentro de ellas existe una relación más precisa entre la cota de los píxeles y la clase de cubierta. Los mapas de elevación y vegetación, más el conocimiento adquirido sobre las características de retrodispersión de Doñana se utilizaron inicialmente para escoger píxeles germen o de origen con elevada confianza en su clase de pertenencia. A continuación, un algoritmo iterativo extiende las regiones germen, incorporando los píxeles adyacentes que son además próximos en distancia de retrodispersión. La cartografía frecuente de inundación a partir de las escenas ASAR permitió identificar distintos eventos de calibración para el modelo hidrodinámico de las marismas de Doñana. Esta investigación también puso de manifiesto que la retrodispersión radar aporta datos adicionales sobre el estado de las marismas, como es el grado de desarrollo de las especies helófitas o la capacidad de discriminar ciertas comunidades vegetales. Es de desear que los conocimientos derivados de este estudio puedan ser aplicados y extendidos con los datos polarimétricos de Doñana que serán adquiridos en breve por modernos radares satelitales. Se trata del sensor canadiense Radarsat-2 y de la constelación europea Sentinel-1, ambos operando en banda C, del sistema japonés ALOS-2/PALSAR-2, en banda L, y de la futura misión española PAZ, en banda X.
Els aiguamolls de Doñana, situats al sud-oest de la Península Ibèrica, experimenten cicles anuals d'inundació a la tardor i d’assecament a la primavera. Com en qualsevol zona humida, la sostenibilitat de Doñana depèn fonamentalment dels seus recursos hídrics. Des de la dècada dels noranta s’han portat a terme importants esforços de seguiment i modelització per a avaluar la salut de l'ecosistema i restaurar tant com sigui possible el seu règim hidrològic natural, per a preveure riscos derivats de les activitats sòcio-econòmiques i del canvi climàtic, i per a dissenyar estratègies d'adaptació que garanteixin la seva sostenibilitat. La present tesi doctoral forma part d’aquests esforços. Entre 2006 i 2010 s’encarregà l’adquisició expressa de nombroses imatges satel·litals de Doñana amb l’objecte d’obtenir observacions regionals i sinòptiques de l'evolució de la superfície inundada als aiguamolls. Amb aquestes observacions es pretenia avançar en el coneixement de la hidrodinàmica del conjunt humit i calibrar el model hidràulic bidimensional del mateix. Aconseguir una freqüència d'observació elevada durant l'ompliment dels aiguamolls fou un requisit d'especial interès, ja que durant aquest període la pluja és més abundant i els processos hidrodinàmics són més ràpids. Les imatges foren adquirides pel sensor radar en banda C ASAR, a bord del satèl·lit Envisat de l'Agència Espacial Europea. La capacitat de la banda C per a travessar la nuvolositat resultà particularment adient per a monitoritzar en detall el procés d'ompliment, ja que aquest està associat amb la presència de núvols. Les imatges ASAR se sol·licitaren en set angles d'incidència diferents per a augmentar la freqüència d'observació, i la majoria d'elles foren adquirides amb la configuració de polaritzacions HH/VV. Durant l'any hidrològic 2006-2007 s’aconseguí un seguiment detallat del procés d'ompliment. Per a aquest cicle es desenvoluparen signatures temporals dels principals tipus de cobertes de Doñana, en els diferents angles d'incidència i polaritzacions disponibles. Les signatures s’analitzaren amb l'ajuda de dades de veritat-terreny per a identificar l'efecte de la inundació en el coeficient de retrodispersió i s’extragueren conclusions sobre la possibilitat de discriminar superfícies emergides i inundades en funció de l'angle d'incidència, tipus de cobertura vegetal i fase fenològica: angles d’incidència intermitjos, com els IS3 i IS4 d’ASAR, resultaren ser els més apropiats per a discriminar superfícies d’aigua lliure en una sola imatge. La cartografia d'inundació als paciles, les regions més elevades, és factible utilitzant angles d’incidència reduïts i intermitjos (entre IS1 i IS4 d’ASAR). En les zones d'elevació intermèdia, colonitzades per grans helòfits, els angles d'incidència grans (IS7 i IS6 d’ASAR) permeten una delimitació de la inundació més precisa durant el desenvolupament de la vegetació fins a aproximadament mitjans d’abril, quan la capacitat de penetració d'aquests angles pot resultar insuficient. Donada la complexa casuística de la retrodispersión de les cobertes de Doñana, la cartografia d’inundació dels aiguamolls sencers a partir d’una sola imatge ASAR fou sovint inviable. Aquesta cartografia s’abordà llavors mitjançant l’ús sinèrgic de les dades ASAR amb el model digital del terreny i el mapa de vegetació de Doñana. L’ús d’entorns de processat irregulars adaptats a la topografia millorà dràsticament el filtrat de les imatges, ja que les vores naturals tendeixen a seguir les corbes de nivell del terreny. Seguidament es dissenyaren algoritmes d’agrupació i classificació de píxels que utilitzen dades ASAR, la cota del terreny i el mapa de vegetació, i que s’apliquen independentment a les diferents sub-conques de Doñana, perquè a dins d'elles existeix una relació més acurada entre la cota dels píxels i el tipus de coberta. Els mapes d'elevació i vegetació, més el coneixement adquirit sobre les característiques del retrodispersió de Doñana s’utilitzaren inicialment per a seleccionar píxels germen o d’origen amb elevada confiança en la seva classe de pertinença. A continuació, un algoritme iteratiu expandeix les regions germen, incorporant-hi els píxels adjacents que són, a més a més, propers en distància de retrodispersió. La cartografia freqüent d’inundació a partir de les escenes ASAR permeté identificar diferents esdeveniments de calibració per al model hidrodinàmic dels aiguamolls de Doñana. Aquest treball de recerca també posà de manifest que la retrodispersión radar aporta dades addicionals sobre l’estat dels aiguamolls, ara com el grau de desenvolupament de les espècies helòfites o la capacitat de discriminar certes comunitats vegetals. És d’esperar que els coneixements derivats d'aquest estudi puguin ser aplicats i ampliats amb les dades polarimètriques de Doñana que seran adquirides properament per moderns radars satel·litals: es tracta del sensor canadenc Radarsat-2 i de la constel·lació europea Sentinel-1, ambdós operant en banda C, del sistema japonès ALOS-2/PALSAR-2, en banda L, i de la futura missió espanyola PAZ, en banda X.

The predictability of beach inundation is mainly related to wave runup and most of the formulations that have been developed focus on the hydrodynamics, disregarding the morphological changes caused during storms. For these reasons, the aim of this thesis is to provide more insight into beach inundation processes at embayed and open beaches and to determine how morphological changes can interfere with these processes. To this end, video measurements of beach inundation and the characteristic morphological changes were carried out at two stretches of coast with different wave climates: the stretch comprising La Barceloneta, Somorrostro and Nova Icaria, which are three artificial, tideless embayed beaches located in Barcelona, Spain (NW Mediterranean); and Noordwijk beach, which is an open, microtidal multibarred beach located in Noordwijk, the Netherlands (North Sea). The effects of a submerged and a detached breakwaters on the morphological and hydrodynamic changes occurring at La Barceloneta during storms is examined in chapter 2. The shoreline response before and after the beach nourishment and the construction of the protective structures was compared using a ten-year video-recorded dataset and hydrodynamics modelled using the SMC model. As a result of the protection works, La Barceloneta was divided into two beaches separated by a salient. A new methodological approach to analyzing beach rotation which eliminates the morphological effect is presented. Results indicate that the beach rotation process has been modified caused by a change in the wave-induced current system from a single dominant alongshore current to one composed of two dominant alongshore currents with opposite directions. In chapter 3, beach inundation affecting the three embayed beaches of Barcelona during the 17 strongest storm events of the period 2001-2008 is analyzed using daily time-exposure images. The shoreline variability due to storms was split into beach planform and morphological features in order to determine its influence on beach inundation measurements. The characterization of the inundation depended on the orientation with respect to the wave direction approach and the morphological features. Beach planform changes are the foremost influence on the inundation of Barcelona beaches. The inundation at the multibarred beach of Noordwijk during the seven strongest storms in the period between 1998 and 2005 is estimated, also using video monitoring techniques in chapter 4. Additionally, the influence of subtidal sandbars on the inundation is analyzed using the XBeach model. To this end, six simulations were carried out using barred profiles measured at Noordwijk but differing in sandbar height and location, and one simulation using a synthetic barless profile. Inundation values ranged from 22 to 105 m, with considerable alongshore variation before the peak of each storm because of the presence of the intertidal bars. The mean inundation values along the beach are well estimated using a simple inundation parameter. The XBeach model shows that the inundation is only affected by the morphology close to the shoreline (i.e. by the intertidal bars or the inner bar if it is wide and closer to shoreline). The outer bar does not seem to influence Beach inundation prediction at Somorrostro beach is evaluated in chapter 5. To this end, inundation measurements using video observations are compared with estimations including the tidal variations and the wave runup formulation of Stockdon et. al (2006) introducing deep water and local wave measurements and computations. The inundation is overestimated if any of the wave heights in the formulation are used. Estimations improved if a local wave height is used, in particular for waves approaching the shore obliquely. Finally, the alongshore variability of the inundation is better captured if the wave runup is assumed proportional to the breaking wave heightBARCELONA07
Las costas están expuestas a la erosión y la inundación producida por los temporales, los cuales son muy frecuentes y pueden producir grandes daños y pérdidas económicas. La inundación producida por los temporales es debida a la marea astronómica y meteorológica y al remonte del oleaje. La predicción de la inundación de la playa está principalmente relacionada con el remonte y la mayoría de las formulaciones propuestas se centran en parámetros hidrodinámicos sin tener en cuenta los cambios morfológicos causados durante los temporales. Por todo ello, el principal objetivo de esta tesis es proporcionar un mayor conocimiento de los procesos de inundación en playas encajadas y abiertas y determinar cómo los cambios morfológicos pueden interferir con estos procesos. Para ello, se han llevado a cabo medidas de la inundación y de los cambios morfológicos característicos utilizando imágenes de video en dos tramos de costa con climas de oleaje diferente: el tramo que comprende las playas de La Barceloneta, Somorrostro and Nova Icaria, las cuales son tres playas artificiales, encajadas y sin marea localizadas en Barcelona, España (NO Mediterráneo); y la playa de Noordwijk, la cual es una playa abierta, multibarrada y micromareal localizada en Noordwijk, Holanda (Mar del Norte). Los efectos de un dique sumergido y un dique exento en los cambios morfológicos e hidrodinámicos ocurridos en la playa de La Barceloneta durante temporales se examinan en el capítulo 2. La respuesta de la línea de orilla antes y después de la regeneración de la playa y de la construcción de las estructuras de protección se compara utilizando 10 años de video imágenes y la hidrodinámica modelada utilizando el Sistema de Modelado Costero (SMC). Como resultado de estas obras de protección, La Barceloneta quedó dividida en dos playas independientes separadas por un saliente. Una nueva metodología para analizar la rotación de la playa que elimina los cambios morfológicos es propuesta. Los resultados indican que la tendencia erosiva previamente observada en la zona noreste de la playa sigue estando presente en la actual playa noreste y está relacionada con el nuevo dique sumergido. Además, el proceso de rotación de la playa se ha modificado, produciéndose solamente en sentido contrario a las agujas del reloj en la playa noreste y en sentido horario en la playa suroeste. Este nuevo comportamiento es debido al cambio en el patrón de corrientes previamente formado por una corriente longitudinal dominante, a un sistema de corrientes compuesto por dos corrientes longitudinales en direcciones opuestas. En el capítulo 3, la inundación producida en las tres playas encajadas de Barcelona durante los 17 temporales más energéticos del periodo 2001-2008 es analizada utilizando imágenes diarias promediadas. La variabilidad de la línea de orilla debida a los temporales es discriminada en cambios en la forma en planta y morfologías (cúspides de playa, megacúspides, ondulaciones y saliente) para determinar su influencia en las medidas de inundación de la playa. La caracterización de la inundación dependió de la orientación respecto de la dirección de aproximación del oleaje y de las morfologías. Los cambios en la forma en planta de la playa son la máxima influencia en la inundación de las playas de Barcelona. Los cambios en la forma en planta hacia tierra y los cambios en el saliente suponen casi un 50% de la máxima inundación medida, mientras que las megacúspides y la ondulación suponen aproximadamente el 25%. El efecto de las cúspides de playa en la inundación es despreciable. Consecuentemente, la variación en la línea de orilla durante temporales influye significativamente los valores de inundación, especialmente en playas con pendientes fuertes. Pequeñas variaciones en la pendiente de la playa pueden sin embargo afectar sustancialmente la inundación en playas con pendientes suaves. La inundación de la playa multibarrada de Noordwijk durante los 7 temporales más fuertes ocurridos en el periodo comprendido entre 1998 y 2005 es también estimada utilizando medidas de video monitorización en el capítulo 4. Además, la influencia de las barras submareales en la inundación es analizada utilizando el modelo XBeach. Para ello, se realizaron siete simulaciones 1-D sin considerar los cambios morfológicos; seis simulaciones utilizando perfiles barrados medidos en la playa de Noordwijk pero que difieren en altura y localización de las barras, y una simulación utilizando un perfil ideal sin barras. Los valores de inundación oscilaron entre 22 y 105 m, con variaciones considerables a lo largo de la playa antes del pico del temporal debido a la presencia de barras intermareales. La inundación promedio a lo largo de la playa es estimada considerablemente bien utilizando un parámetro de inundación sencillo que incluye la pendiente intermareal y supramareal, la altura de ola y la longitud de onda en aguas profundas y la marea meteorológica. El modelo XBeach muestra que la inundación está solamente afectada por la morfología próxima a la línea de orilla, esto es, por las barras intermareales o por la barra interna si es ancha y próxima a la orilla. La barra externa no parece tener influencia en el comportamiento de la inundación. La predicción de la inundación en la playa de Somorrostro es evaluada en el capítulo 5. Para ello, medidas de la inundación utilizando observaciones de imágenes de video se comparan con estimaciones de la inundación incluyendo las variaciones de la marea y el fórmula del remonte de Stockdon et al. (2006), introduciendo medidas locales y en aguas profundas del oleaje así como oleaje modelado. Debido a que las observaciones corresponden a un remonte medio y las estimaciones usan el remonte excedido un 2% (R2%), la inundación es sobreestimada para cualquier altura de ola utilizada en la fórmula. Sin embargo, las estimaciones mejoran si una altura de ola medida a 10 m es utilizada en la fórmula en particular para oleajes con una aproximación oblicua a la línea de orilla. Finalmente, las diferencias entre las observaciones y las estimaciones varían a lo largo de la playa, siendo mayores en la zona de curvatura de la playa. La variabilidad de la inundación a lo largo de la playa es mejor caracterizada si el remonte se asume igual que la altura de ola en rotura.

A big responsibility lies in the hand of local authorities to exercise measures in preventing fatalities and damages during flood occurrences. However, the problem is how flooding can be prevented if nobody knows when and where it will be occurring, and how much water is expected. Therefore, the utilisation of flood models in such studies can be helpful in simulating what is anticipated to occur.

 

In this study, the HEC-RAS steady flow model was used in calibrating different flood events in Testeboån river, which is situated in the municipality of Gävle in Sweden. The purpose is to provide inundation maps that show the water surface profiles for the various flood events that can help authorities in planning within the area. Moreover, the study would try to address certain issues, which concern one-dimensional models like HEC-RAS in terms of the effects of topographic data and the parameters used for friction coefficient.

 

Various flood maps were produced to visualise the extents of the floods. In Oppala and Norra Åbyggeby, the big water extents for both the 100-year and the highest probable floods were visible in the forested areas and grasslands, although a few houses were within the predicted flooded areas. In Södra Åbyggeby, Varva, Forsby, and in the northern parts of Strömsbro and Stigslund, the majority of the residential places were not inundated during the 100-year flood calibration, but became flooded during the maximum probable flood. The southern portions of Strömsbro and Stigslund had lesser flood extents and houses were situated within the boundaries of the highest flood. In Näringen, there were also some areas close to the estuary that were flooded for both events.

 

With the other calibrations performed, two factors that greatly affect the flood extents in the floodplain, particularly in flatter areas were topographic data and the parameters used as friction coefficient.  The use of high resolution topographic data was important in improving the performance of the software. Nevertheless, it must be emphasised that in areas characterised by gentler slopes that bounded the channel and the floodplain, data completeness became significant whereby both ground data and bathymetric points must be present to avoid overestimation of the inundation extent. The water extents also varied with the use of the various Manning’s n for the overbanks, with the bigger value showing greater water extents. Else, in areas with steeper slopes and where the water was confined to the banks, the effect was minimal.

 

Despite these shortcomings of one-dimensional models, HEC-RAS provided good inundation extents that were comparable to the actual extent of the 1977 flooding.

 

Modelling real floods has its own difficulties due to the unpredictability of real-life flood behaviours, and more especially, there are time dependent factors that are involved.  Although calibrating a flood event will not exactly determine what is to arise as they might either under- or overestimate such flooding occurrences, still, they give a standpoint of what is more or less to anticipate, and from this,  planning measures can be undertaken.

Climate change is expected to result in more frequent occurrences of extreme flood events, such as flash flooding and large scale river flooding. Therefore, there is a need for accurate flood risk assessment schemes in areas prone to extreme flooding. This research study investigates what flood risk assessment tools and procedures should be used for flood risk assessment in areas where the emergence of extreme flood events is possible. The first objective was to determine what type of flood inundation models should be used for predicting the flood elevations, velocities and inundation extent for extreme flood events. Therefore, there different flood inundation model structures were used to model a well-documented extreme flood event. The obtained results suggest that it is necessary to incorporate shock-capturing algorithms in the solution procedure when modelling extreme flood events, since these algorithms prevent the formation of spurious oscillations and provide a more realistic simulation of the flood levels. The second objective was to investigate the appropriateness of the “simplification strategy” (i.e. improving simulation results by increasing roughness parameter) when used as a flood risk assessment modelling tool for areas susceptible to extreme flooding. The obtained results suggest that applying such strategies can lead to significantly erroneous predictions of the peak water levels and the inundation extent, and thus to inadequate flood protection design. The third and final objective was to determine what type of flood hazard assessment methods should be used for assessing the flood hazard to people caused by extreme flooding. Therefore, two different flood hazard assessment criteria were modelled for three extreme flood events. The predicted results suggest that in areas prone to extreme flooding, the flood hazard indices should be predicted with physics-based formulae, as these methods consider all of the physical forces acting on a human body in floodwaters, take into account the rapid changes in the flow regime, which often occur for extreme events, and enable a rapid assessment of the degree of flood hazard to be made in a short time period.

Flood plain mapping has become an increasingly important part of flood plain management. Flood plain mapping employs mapping software and hydraulic calculation packages to efficiently map flood plains. Modelers often utilize automation software to develop the complex geometries required to reduce the time to develop hydraulic models. The Utah Inundation Mapping System (UTIMS) is designed to reduce the time required to develop complex geometries for use in flood plain mapping studies. The automated geometries developed by UTIMS include: flood specific river centerlines, bank lines, flow path lines, cross sections and areal averaged n-value polygons. UTIMS thus facilitates developing automated input to US Army Corps of Engineer's HEC-RAS software. Results from HEC-RAS can be imported back to UTIMS for display and mapping. The user can also specify convergence criteria for water surface profile at selected locations along the river and thus run UTIMS and HEC-RAS iteratively till the convergence criterion is met. UTIMS develops a new flood specific geometry file for each iteration, enabling an accurate modeling of flood-plain. Utilizing this robust and easy to operate software within the GIS environment modelers can significantly reduce the time required to develop accurate flood plain maps. The time thus saved in developing the geometries allows modelers to spend more time doing the actual modeling and analyzing results. The time thus saved can also result in faster turn around and potential cost cutting in flood-plain modeling work. In this paper the authors describe UTIMS capabilities, compare them with other available software, and demonstrate the UTIMS flood plain automation process using a case study.

This research assesses possible methods for extending the Streamflow Prediction Tool from a streamflow forecasting model to a flood extent forecasting model. This new flood extent forecasting model would allow valuable and easy to understand information be disseminated in a timely manner for flood preparation and flood response. The Height Above Nearest Drainage (HAND) method and AutoRoute method were considered for flood extent models but the HAND was the better option for its simple and quick computation as well as its viability on a global scale. Due to the importance of Digital Elevation Models (DEMs) in these flood extent models, an analysis was performed on the sensitivity and response of different DEMs with the HAND method. The HAND method with the differing DEMs was also analyzed using the Streamflow Prediction Tool for model boundary conditions against Sentinel-1 SAR generated flood extent images from August 24, 2017. The MERIT DEM performed the best in this analysis and is recommended for future research in creating a global forecasting flood extent model. The HAND method covered about 25% of the generated flood extent images and more complex flood extent models may need to be considered in areas where HAND underperforms. Finally, a proof of concept flood extent model was created and deployed as a web application for easy accessibility and distribution of flood information. Additional research to consider is flood impact based on affected population or an economic analysis, as well as optimizing model parameters for increased accuracy and performance. Additional research is also needed for HAND DEM analysis in other parts of the world.

We develop a Bayesian framework for calibrating flood inundation simulators on an observation of flood extent, and making calibrated predictions of a future event. We illustrate the framework using the binary channel (BC) model for the likelihood of the observed flood extent given a simulation of flood extent. The BC model leads to poor results, and this motivates the search for a more appropriate likelihood model, which forms the basis for the rest of the thesis. We extend the Ising model to regression on a binary image and review methods for dealing with the intractable normalising constant. We propose novel applications of path sampling, extend path sampling to sampling over areas, and develop approximations to path sampling. We also develop the heterogeneous binary channel (HBC) model to test the effect of heterogeneity and spatial dependence. We extend the hidden conditional autoregressive (HCAR) model to regression on a binary image. We show that the limit of the HCAR model as the parameters approach the boundary is the (improper) hidden intrinsic autoregressive (HIAR) model. We prove that the HIAR model can be used for calibration but not calibrated prediction. We develop a number of methods for improving mixing of the MCMC algorithm. We explore two extensions of the HCAR model. First the heterogeneous HCAR (HHCAR) model, which represents heterogeneity, and second the continuous HCAR (CHCAR) model, which uses continuous simulation values. In conclusion, using our Bayesian framework we can replicate the results of less rigorous approaches, for example generalised likelihood uncertainty estimation (GLUE), and make probabilistic predictions which are not possible in these less rigorous approaches. Future work would further develop the likelihood models.

Since 1962 storage cell codes have been developed to simulate flow on fluvial and coastal floodplains. These models treat the floodplain as a series of discrete storage cells, with the flow between cells calculated explicitly using some analytical flow formulae such as the Manning equation. Recently these codes have been reconfigured to use regular Cartesian grids to make full use of widely available high resolution data captured from remote sensing platforms and stored in a raster GIS format. Such raster-based storage cell codes have many of the advantages over full two-dimensional depth averaged schemes but without the computational cost, however their typical implementation results in a number of fundamental limitations. These include an inability to develop solutions that are independent of time step or grid size, and an unrealistic lack of sensitivity to floodplain friction. In this thesis, a new solution to these problems is proposed based on an optimal adaptive time step determined using a Courant-type condition for model stability. Comparison of this new adaptive time step scheme to analytical solutions of wave propagation/recession on flat and sloping planar surfaces and against field measurements acquired for four real flood scenarios demonstrates considerable improvement over a standard raster storage cell model. Moreover, the new scheme is shown to yield results that are independent of grid size or choice of initial time step and which show an intuitively correct sensitivity to floodplain friction over spatially-complex topography. It does, however, incur a prohibitive computation cost at model grid resolutions less than 50 m. This primary research is supplemented by an examination of the data and methods used to apply, and in particular calibrate, distributed flood inundation models in practice. Firstly, different objective functions for evaluating the overall similarity between binary predictions of flood extent and remotely sensed images of inundation patterns are examined. On the basis of the results presented, recommendations are provided regarding the use of various measures for hydrological problems. Secondly, the value of different observational data types typically available for calibrating/constraining model predictions is explored within an extended Generalised Likelihood Uncertainty Estimation (GLUE) framework. A quasi-Bayesian methodology for combining these individual evaluations that overcomes the limitations of calibration against any single measurement source/item is also presented.

Our landscape is constantly evolving, and so to are our rivers. These changes can be perturbed due to many factors, including land use and climate change. But also changes in river morphology is a dynamic process that constantly evolves, particularly during extreme flood events. This can result in significant changes in channel morphology over short periods of time. Rivers, and the amount of flow they can convey within bank before their channel capacity is reached, is critical to predicting the extent of flood inundation in both rural and urban areas. An important research question is therefore to what extent are fluvial geomorphological changes critical to the prediction of flood inundation extents during and between events? Furthermore how uncertain are these processes and so can their effects be quantified within a risk based framework? This PhD tries to answer those questions using state-of-the-art flood simulation techniques that also comprehensively characterises the inherent uncertainties involved. Most flood modeling studies ignore the potential for morphological changes to alter channel conveyance and bed roughness, in and between large events. Furthermore the overall bedload and geomorphological catchment processes upstream are rarely considered, particularly within an uncertainty analyses framework. The research here within uses the following approaches to characterize this in 3 core results chapters: Chapter 4 uses simple approach to quantifying the potential changes in channel erosion that occur in flooding events to see the sensitivity to the resultant flood inundation extents predicted for the Cockermouth 2009 November flood event. Chapter 5 applies a catchment scale landscape evolution· model CAESAR-Lisflood to two catchments upstream of Cockermouth within an uncertainty analyses framework. This explored the use of uncertain data in• constraining the model simulations for the period of record available. Chapter 6 uses the constrained (behavioural) model simulations found in chapter 5 to simulate flood events at Cockermouth to see the impact of dynamic geomorphological changes during flood events to the predicted extent of flood inundation and flood depths. The results showed that by the inclusion of sediment transport this greatly changed flood dynamics both in terms of water depth and flow volume, with a wider bound of uncertainty quantified in the flood predictions generated. This has important implications for understanding and predicting flood risk across a range of catchments, particularly those that are more susceptible to ongoing geomorphological changes. Futhermore with the inclusion of sediment transport and the consideration of morphological changes, the uncertainties inherent in the observation data which were used to constrain the catchment behaviour had been accounted for and propagated to the downstream reach. This research showed that the prediction uncertainty bounds had been significantly widened in flood inundation extent, flood volume, and water depths. This reveals that the importance of connectivity between catchment dynamics and downstream behavior and flooding at reach scale cannot be examined in isolation from upstream. Hence, it is important and necessary for flood inundation modeling to consider the associated uncertainties from geomorphological impacts and incorporate both hydrodynamic and morphodynamic aspects for subsequent flood risk assessment.

Numerous efforts have been employed to explore plausible future sea level rise range as well as improving the ice sheet dynamic that was considered as the biggest challenge in sea level projections. These results in the availability of numerous corresponding Global Mean Sea Level (GMSL), a property that exhibits the problem of deep uncertainty. In the front of deep uncertainty problems, the paradigm "predict then act" is no longer sufficient, as decision makers are prompted with the more recent framework that could encompass the latter problem, in this case, the Robust Decision Making (RDM) approach. Nacka Municipality, one of the rapid growing municipalities in Stockholm, must face future sea level rise problem under this circumstance, which requires an input to be able to act against sea level rise while also sustaining the development in the area. This work will connect three main methods to provide an appropriate flood map for robust decision-making processes, namely the localization of GMSL, extreme value analysis, and hydrodynamic models. Localizing the GMSL is done by incorporating several important aspects (i.e. Vertical Land Motion, Ocean Dynamics, and Ice Melt Dynamic). Extreme value analysis was conducted to project the extreme value of sea level and the wind according to the desired return period outcome. While hydrodynamic model will provide a more representative interaction between the phase: sea, wind and bed properties. The latter will be done using a product created from the Danish Hydrological Institute (DHI) named MIKE 21 FM. The latter features flexible mesh as the main element and allows to incorporate the momentum equation into place. Furthermore, results will be based on two scenarios: extreme and low in two different time frame, namely 2100 and 2150. Results will explore the area span of the flood as well as the potentially impacted buildings. Additionally, both scenario results will be adjoined per time frame to provide a span of flood area between the low and the extreme scenarios.
Flera områden i Nacka Kommun ligger vid Östersjöns kust och inom dessa kustnära områden finns infrastruktur som tjänar en värdefull funktion för samhället. Det finns en växande oro att dessa platser kommer hotas av förändrade havsnivåer, både på kort och på lång sikt. Denna studie kommer att undersöka effekten av översvämningar på kustområden i Nacka genom att titta på kanalen från Ekorren till Solsunda tillsammans med en djupgående diskussion om Fisksätra och Tollare. Som en försiktighetsåtgärd föreslår Länsstyrelsen i Stockholm en anpassningsåtgärd att värdefull infrastruktur byggs över 2,7 meter. En uppskattning av tröskelvärdet bör också diskuteras ytterligare. Havsnivåförändringar bör uppfattas som händelser som innefattar flera scenarier och som inte går att fullständigt hantera med paradigmet "förutse sen agera". För att ta itu med detta har en modell utformats för att bedöma två uppsättningar villkor som står i kontrast med varandra och som kommer att fungera som ett intervall, det låga och det extrema, samt två tidsramar: år 2100 och år 2150. Ett lågt scenario bedömer den låga förändringen av havsnivån i kombination med extrema värden för vattennivån och en vindhastighet som motsvarar 100 års returperiod. I motsats hanterar det extrema scenariot den extrema förändringen av havsnivån samt en 1000 års returperiod med extrem havsnivå och vindhastighet. När det extrema vindhastighetselementet bortses, kommer de framtida vattennivåer som kommer att användas vara följande: 1,70 m för låg 2100; 3,63 m för extrem-2100; 2,15 m för låg 2150; Och 6,35 m för extrem-2150. Hastigheten för havsnivåförändringen är tagen från den globala genomsnittliga havsnivåförändringen som har anpassats till lokal havsnivåförändring specifikt för Stockholm. Lokala fysiska attribut ingår också, t.ex. vertikal markrörelse, havsnivå, vind- och bäddmotstånd från markskyddet. För att kunna bearbeta alla dessa ingångsvärden använder studien MIKE 21 Flexible Mesh Hydrodynamic modul skapad av DHI. Sammantaget påverkas de kustområden som ligger inom ramen för studien mindre av kustöversvämningar. Detta beror på den branta terrängen nära kanalen. Det finns dock flera undantag, speciellt vid extrema scenarier och värst på längre sikt, såsom delområdena Saltängen, Saltsjö-Duvnäs, Lännersta och Ekorren. Anledningen att de är känsliga för förändring beror på den relativt plana terrängen nära kanalen. De drabbade byggnaderna i dessa scenarier är bostäder, affärsbyggnader och flera skolor. För de två mer berörda områdena i denna studie är Tollare mindre påverkad av kustöversvämningar i alla scenarier jämfört med Fisksätra. Länsstyrelsens förslag att bygga över tröskelvärdet på 2,7 meter visar sig vara tillräckliga vid låga scenarier. I vissa andra fall föreslog översvämningsmodellen att dessa regler och begränsningar är otillräckliga, i synnerhet i samband med extrema scenarier och långsiktiga händelser. Vidare måste anpassningsåtgärder på längre sikt omprövas för att kunna hantera eventuella framtida händelser.

In the last few centuries, many streams in the eastern United States have been severely disturbed by land use change and are now disconnected from their original floodplain due to the aggradation of legacy sediment. Currently, stream-floodplain reconnection is advocated as a stream restoration practice to take advantage of ecosystem services. The objective of this study is to compare two current stream restoration approaches for their nutrient flushing ability: 1) a conventional approach leaves legacy sediment on the floodplain; and 2) an ecological approach that involves removing the accumulated legacy sediment in order to restore the original floodplain surface wetland, revealing a buried A soil horizon. Soil cores were taken from the surficial legacy sediment layer and the buried A soil horizon in the floodplain of a 550-meter reach of Stroubles Creek in the Valley and Ridge province near Blacksburg, VA, to evaluate potential for flushable DOC, TDN, NO3-, NH4+, and SRP content. In addition, an inundation model was developed to evaluate the extent of flooding under the two restoration scenarios. The inundation model results and nutrient flushability levels were then used to simulate the release of nutrients as a function of stream restoration approach. Results indicate that the buried A horizon contained less flushable nutrients, but the ecological restoration would have a higher frequency of inundation that allows for more flushable nutrient release at the annual scale. Understanding the nutrient release potential from the floodplain will provide the ability to estimate net nutrient retention in different stream-floodplain reconnection strategies.
Master of Science

碩士
中國科技大學
土木與防災應用科技研究所
98
Taiwan is located in subtropical regions, the island surrounded by the sea. The average annual rainfall of about 2,510 mm. Flood disasters often generate in summer and autumn. Simulation and application of past flood have good results. The flood simulation always needs longer time. The rainfall data is automatic rainfall station data. Rainfall data is less in the region. So the forecasting method cannot provide reliable information. Therefore, this study will establish a simple and quick to flood early warning system, using potential inundation map and geographic information system set up rain - flooded area charts regression equations, then NSC (Develop the radar rainfall forecasting Technique for Basin) by the integrated development of radar rainfall data QPESUMS flood forecasting and regression for each region to find flood warning rainfall values. The study area selected for the Taiwan County, and historical events using the Typhoon 2008 Typhoon KALMAEGI, FUNG-WONG typhoon, Typhoon SINLAKU, JANGMI typhoon simulation verification, and then to MORAKOT in 2009 and typhoons Typhoon PARMA flood forecasting. The results show that the disaster warning point with the real disaster fairly consistent, forecasting the outcome of this research note shows warning means flooding has achieved much success in the application. This method can make flood warning and forecasting of rainfall by using QPESUMS radar to calculate the individual area of the flooded area, and this information provides disaster prevention unit, expected to reduce the occurrence of disasters.

碩士
中原大學
土木工程研究所
104
This research integrates web geographic information system (GIS) technology and two dimensional inundation model (2DIM) to develop an inundation simulation system (ISS). ISS employs apache web server, MapServer, HTML (hyper text markup language), CSS (cascading style sheets), JavaScript, and PHP programming languages to develop online user interfaces allowing users to input rainfall data directly from browsers. ISS then simulates inundation and transforms the simulated results to spatial information. The results can be shown on the web using MapServer, web GIS technology. This simplifies the process of simulation using 2DIM by hand. Five cases, Luzhou and Sanchong District in New Taipei city area, Dianbao river catchment in Kaohsiung city area, Zhuangwei Township in Yilan County area, Wujie Township in Yilan County area, Yilan City area, are selected in this research to test ISS during system development and test phases. ISS chooses a single rainfall event for each case to simulate inundation and transforms the simulated results to spatial information. The simulated results are compared with that simulated by original way – a step by step approach – that 2DIM simulates inundation and then exhibits the results using ArcGIS software. It shows that it is feasible that ISS can be applied to execute 2DIM and to display geospatial data online. This reduces the complexity of simulation and reaches the objective of real-time simulation.

碩士
逢甲大學
水利工程所
95
Owing to geographic location of Taiwan being on subtropical monsoon zone, so typhoons and storms occur frequently. Typhoons and storms during summer and fall always cause several flooding, flood damages, and human lives loss in Taiwan. The major factors that cause flooding, landslide, and debris-flow in Taiwan are typhoons and storms of monsoon rain season. The function of hydraulic structure has its limit, it must cooperate with urban flood improvement action to mitigate flood damages. The urban flood improvement action must improve the locations of flood area, flood depth, flood duration, and calculate flood damages in the floodplain when heavy rainfall happens and effective mitigately the flood disaster loss. We present a two-dimensional unsteady flow model bases on the TVD finite difference method with structured grids in basin system. The Digital Terrain Model (DTM) and Geographic Information System (GIS) are employed to treat the input and output data for the model. The final global of this project is to simulate Sanchong area and provide the most important information, including the inundation range and depth for Sanchong. As an important aid to the flood improvement action review and evaluation for warming policy, and prepare step of decision. Then, we test the suitability of this model on Sanchong area, and present the result and discuss.

碩士
國立交通大學
土木工程學系
99
Sewer systems, which are one of the basic constructions of modern city, have main function of draining surface runoff for preventing the occurrence of inundation events. Therefore, maintaining the normal function of sewer systems working is the core issue of city’s drainage. However, proper maintenance of sewer system has been ignored for a long time. Both human activities and natural effects cause egregious impacts on sewer systems, such as flux of sludge, illegal emission of waste water for washing sand, arbitrarily placing miscellaneous articles, and pipes crossing irregularly. 　　This study first chooses SOBEK model as the numerical tool, which is usually used in WRA’s projects of simulating and managing easy flooding areas, and the model’s numerical methods, flowcharts, grid generation, and other functions. Second, the calibration and verification of SOBEK model is executed for the watershed of Yu-Cheng Pump Station in Taipei. Finally, the inundation areas and depths of the study area are evaluated under the conditions of different deposition levels and reaches of the sewer system.

碩士
國立臺灣大學
生物環境系統工程學研究所
97
Taiwan is located at a special point, which is in the path of typhoons from northeast Pacific Ocean. Taiwan is also situated in a tropical-subtropical transition zone. As a result, rainfall is abundant all the year round, especially in summer and autumn. For flood inundation analysis in Taiwan, there exist a lot of uncertainties in hydrological, hydraulic and land-surface topography characteristics, which can change flood inundation characteristics. According to the 7th work item of article 22 in Disaster Prevention and Protection Act, for preventing flood disaster being deteriorating, investigation analysis of disaster potentials, hazardous degree and situation simulation must be proceeded with scientific approaches. However, the flood potential analysis uses a deterministic approach to define flood inundation without considering data uncertainties. This research combines data uncertainty concept in flood inundation maps for showing flood probabilities in each grid. It can be an emergency evacuation basis as typhoons come and extremely torrential rain begin. The research selects Hebauyu watershed of Chiayi County as the demonstration area. Owing to uncertainties of data used, sensitivity analysis is first conducted by using Latin Hypercube sampling (LHS). LHS data sets are next input into an integrated numerical model, which is herein developed to assess flood inundation hazards in coastal lowlands, base on the extension of the 1-D river routing model and the 2-D inundation routing model. Finally, the probability of flood inundation simulation is calculated, and the flood inundation probability maps are obtained. Flood Inundation probability maps can be an alternative of the old flood potential maps for being a regard of building new hydraulic infrastructure in the future.

碩士
國立交通大學
土木工程系所
104
In recent years, Global climate anomaly, Taiwan also. Typhoons and heavy rainfall often cause flooding that result in serious losses of life and property in summer and autumn. The population and development of socio economic is related to hazard of extreme weather. Therefore, this study use non-engineering methods to reduce hazard by risk map. Flood map of Taiwan only have water depth and inundation area in the past, it is difficult to recognize where is the disaster area, therefore, this study reference different research of risk analysis, adding concepts about Hazard and Vulnerability. Delimit Risk = Hazard cross Vulnerability, and use different return period inundation model to produce Hazard map and Vulnerability map.Then, use semi-quantitation risk matrix to produce Risk map. The drainage systems in the Sanyei in Tainan are taken as a case study. Use SOBEK model with a regular grid in 10m resolution, and simulates the return period 2-year, 5-year, 10-year, 25-year, 50-year and 100-year in village level to get distributed of high risk village. The analyzing results can help the city government to realize the most risk area to reduce rescue time, and also let people who live in the high risk area have information to prevent disaster.

碩士
國立成功大學
水利及海洋工程學系
88
When all industries are promoting, the researches about hydraulic engineering have to use the computing machines effectively to computerize and automate to promote the level of the researches. We used geographic information system( GIS ) to generate inundation cells of physiographic regional inundation and drainage model(PRID-model) automatically in this paper. The automatic processes transfer factitious judgments to well-established rules and orders and that will economy manpower, decrease factitious errors and promote the value of the PRID-model. In this research, we take the watershed of Tsengwen river and Yenshui river and the plain between the downstream of Tsengwen river and Yenshui river to study and according to the geography and the geomorphy of the watershed, and the functions of grid analysis and overlay analysis of GIS to generate inundation cells automatically and give each cell hydrologic parameters automatically. We also use the method of generating inundation cells automatically to PRID-model to simulate inflow and sluice process of Tsengwen reservoir and inundation phenomenon on the plain between the downstream of Tsengwen river and Yenshui river duration Dawg typhoon.

碩士
國立彰化師範大學
地理學系
98
Floods are the most devastating natural disasters that cause numerous damages and casualties. Due to the fierce climate change worldwide, the threat of floods puts life in risk, especially for Taiwan, which is unique in its climate, geology and terrain, becomes the concern of high risk. Changhua County, one of the areas frequently devastated by floods, was selected as the setting of this research. In 2001, National Science and Technology Center for Disaster Reduction has completed all the city potential inundation maps in Taiwan. However, only a few were applied in relevant research with limited contribution. As a result, this research aimed to overlay the potential inundation maps and the land use maps of Changhua County to investigate the inundation in farmlands, industrial estates, commercial and residential areas. Besides, grades are given to each of the three areas in each town and village according to the scale of inundation. The grades are summed up to judge the vulnerability of each town and village. The results show that the farmlands in Erhlin are the most devastated, while industrial estates, commercial and residential areas are damaged the most in Changhua City and Yuanlin. In terms of vulnerability evaluations, Changhua City, Fangyang and Dacun are the most vulnerable areas under smaller floods. Changhua City, Fangyang, Fusing and Puyan are most vulnerable under extreme flooding events. In addition, data of agriculture loss and inundation grant application were collected for verification of the overlapping analysis. Furthermore, demographic data of every town and village were collected for the discussion of vulnerability. The results indicated a consistency between most of the potential inundation of farmlands and the real damages except Jhutang and Fangyang. The number of victims in the residential area also corresponded to that of the inundation grant application. Hence, the research proved the value of the potential inundation maps. Moreover, the results suggested that the southwestern towns and villages in Changhua County are significantly vulnerable in terms of demographics, which deserves special attention from the authority. Keywords: inundation vulnerability, potential inundation maps, land use, Changhua County

碩士
國立臺灣大學
生物環境系統工程學研究所
96
Although traditional inundation models have been applied with good accuracy in Taiwan, they usually require a long computing time for simula-tions. However, the meteorological and geographical conditions in Taiwan frequently cause inundation within a short time period when storm occurs. The lead-time for emergency response in too short to indicate the areas with high flood risks for evacuation by using the traditional inundation models. The study aims to establish an inundation model for Taiwan and inte-grate the QPESUMS system which constructed and developed by the Cen-tral Weather Bureau. The radar precipitation by the QPESUMS system, as well as the rain-gauge records, are considered in the inundation model for real-time simulations. The precipitation data of typhoon NARI were simu-lated and evaluated different scale of grid size that the accuracy and effi-ciency of model would be suggested for practical applications. The Keelung River basin is adopted as the study areas of the inunda-tion model. By use of QPESUMS radar precipitation for the typhoon HAITANG and KROSA, the inundation simulations can be calculated in a short time. The model will be executed in the future, to simulate the flood scenarios induced by the occurring and the forecasted rainfalls. The inun-dation will be predicted in 1-3 hours ahead to help the emergency managers taking proper strategies for disaster mitigations.

碩士
淡江大學
水資源及環境工程學系
90
Rapid Transit System is one of the most important items of transportation development in the future. It’s definitely hard to estimate the damages of suffering from the flood because most of the systems in metropolitan are underground. Since the serious damages of whole Rapid Transit System in Taipei caused by Nari typhoon last year. So it’s very important to avoid the flood damages in Rapid Transit System. This thesis shows the Ching-Mei and the Ta-PingLin stations－as testing areas, and use the data from Nari typhoon as an example to perform flood simulation based upon geographic information systems, which uses ArcView and ARC/INFO software in obtaining parameters for flood modeling and the display of simulation results. Finally, comparing with the true situation and point out some tactics and measures in academic and engineering application.

碩士
國立屏東科技大學
土木工程系所
96
This study used inundation model to simulate flooding situation during rainstorm period. The surface slope directly influences depression storage and flow direction of surface runoff. But precision of the numerical computation is decided by grid resolution. This research using the FLO-2D model simulates flooding ambit and depth with 200 year return period in one day raining within sub-watershed in Lee-Chai Creek, Taidong County. Five types of grid resolution, 40 m × 40 m, 80 m × 80 m, 120 m × 120 m, 160 m × 160 m, and 200 m × 200 m were conducted to simulate inundation situation that purpose was to answer the impact of ambit and depth on grid resolution. The analytic results showed the flooding grid numbers and area increased in higher resolution conditions during flooding depth greater than 30 cm. This suggested higher grid resolution can reveal the local low-lying terrain change, but higher grid resolution had progressively increased time to compute flooding situations.

碩士
淡江大學
水資源及環境工程學系碩士班
97
The typhoon events usually cause downstream flooding in Taiwan. Estimation the flood depths and extent may provide the flood inundation information that will be helpful to deal with some contingencies, then alleviate the risk and losses of the flood disasters. The conventional simulations of flood inundation extent need a huge amount of data and computing time by using a series of numerical models. The study proposes the hybrid models to build the regional flood inundation estimation model. In order to figure out the causes of the flood inundation, the correlation analysis and factor analysis are used to explore the relationship between flood inundation influence factors; then K-means clustering is used to categorize the data points of the different flooding characteristics and to find the control point in each flooding group. The hybrid models are composed of three types of models in each flooding group: a single back-propagation neural network (BPNN) for each control point, the linear regression models for the linear grids and a multi-grid BPNN for the nonlinear grids. Two study areas, Fonshang city, Kaohsiung County, and Yuanlin township, Changhua County, are tested for evaluating the practicability and accuracy of the proposed approach. The results show that the proposed hybrid models can accurately and timely estimate the simulated flood inundation extents and depths.