Storm surges induced by tropical cyclones have been ravaging coastal communities worldwide, where a growing number of people reside. Tremendous life and economic losses are caused by tropical cyclones, contributing to more than half of the damages induced by natural hazards. To improve the resilience of coastal communities to surge hazards, it is of great importance to provide reliable and efficient real time forecasts of the spatiotemporal evolution of storm surge, as well as reliable predictions of the probabilistic surge hazards under future conditions. Three specific goals are addressed in this work. Studies on characterization and prediction of surge before a hurricane landfall show that a dimensionless relationship between intensity scaled surge magnitude and wind-duration scaled surge timing may effectively be used for rapid and reliable forerunner surge forecasting. Investigation of how probabilistic surge hazard changes with sea level rise (SLR) shows that the probabilistic surge with SLR can be 1.0 m larger, while different individual storm's surge with the same magnitude can be 1.5 m larger or 0.1 m smaller, indicating the importance of not relying on results from a limited number of storm surge events to assess the probabilistic surge hazard change to SLR. Finally, studying the temporal evolution of coastal flooding changes with SLR shows forerunner surge responds differently to SLR than peak surge, and that storm forward speed is a key factor determining the forerunner-SLR response. / Ph. D.

There is a growing need to improve the understanding of the behaviour of infrastructure in permafrost regions. Permafrost affects nearly half of the land surface in Canada, especially in the north. Further development of natural resources in northern Canada will provide socio-economic benefits to the region and its residents. Linear infrastructure, such as highways, is an important part of that development. The integrity of infrastructure in northern regions is negatively impacted by thawing and degradation of the underlying permafrost initiated by changes in both air and ground temperatures. Subsequent deformations due to settlement and lateral spreading can lead to potentially hazardous driving on highways. The author’s research focused on a section of highway embankment on Provincial Road (PR) 391 located 18 km north of Thompson, Manitoba. The purpose of the research was to further understanding of the thermal and deformation behaviour of an embankment subjected to degrading permafrost conditions. The author’s research consisted of laboratory testing, instrumentation installation, data monitoring, and numerical modelling. Laboratory tests on four-inch (101.6 mm) diameter Shelby tube samples characterized the soil at the site. Data were collected remotely via satellite, and included ground temperatures, pore water pressures, and displacements both laterally and vertically. Ground temperatures indicated a frost bulb, a region of frozen ground, under the embankment. Thermal models using TEMP/W simulated the current ground thermal regime and projections of future thermal behaviour of the embankment. Deformation numerical models using SIGMA/W incorporated changes in the size of the frost bulb over a freeze-thaw cycle to simulate the deformation behaviour of the embankment. The numerical models were compared with the collected data.

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / In this article, a comparative analysis is performed between one-dimensional (HEC-RAS) and two-dimensional (IBER) models, in the evaluation of total scour in the pillars and abutments of a bridge. The case study is the Huallaga bridge, located in the San Martín region, Peru.Based on the geomorphological, hydrological and hydraulic data of the study area and after carrying out an analysis of the different equations for local, general scour; Numerical modeling was performed on the HEC-RAS and IBER software in order to calculate the depths of the scour.The following results were obtained: That in the local scour calculations, the scour depths were less with the 2D software, compared to the values obtained in the 1D software; while in general scour calculations, we obtain greater depths when modeling with 2D software, compared to the values obtained in 1D software

This research has been undertaken to further our knowledge of decade-to-century timescale braided, gravel-bed river delta growth dynamics. The study included: a review of available literature; field studies; the development of microscale models for two study deltas; and the development of a simple numerical model incorporating movement of braided river channels across a delta topset (varying the location of sediment delivery to the delta). Results from the microscale modelling showed that successful physical modelling requires well-defined fixed boundaries and, ideally, good historical aerial photography for the estimation of the model time scale. A complex braided gravel-bed river delta system composed of two merging deltas entering a deep, low-energy receiving basins was able to be successfully modelled to provide valuable information on delta growth dynamics. However, a microscale model of a delta prograding into shallow receiving basins, with a large supply of fine sediment, was more difficult to calibrate and assess (partly due to limited field data), and was considered less reliable. The simple rule-based numerical model ‘DELGROW’, developed to simulate a braided river system entering a deep, low-energy body of water, requires a known sediment supply rate, as well as information on the braided river topography, submerged delta foreset, and lakebed bathymetry. Unlike simple 1-d width-averaged geometric models, DELGROW takes into consideration barriers (e.g. islands) as well as relatively complex converging braided river delta configurations. By changing the sediment supply, or modifying the river system, the response of the river system to various scenarios can also be assessed. Microscale models and DELGROW appear to realistically simulate decade-to-century timescale growth of braided gravel-bed river deltas entering a deep, low-energy, receiving basin. Both of these modelling methods initially use the supplied sediment to try and eliminate any riverbed irregularities (e.g. low areas), before continuing to advance and deposit sediment in a more evenly-distributed manner, whilst taking into consideration irregularities due to barriers, and asymmetric sediment sources such as merging deltas. Neither model can reliably predict locations of bank erosion, or channel avulsions that divert flow and sediment outside of the fixed model boundaries.

A thermal conductive heating (TCH) pilot test was conducted at the Naval Air Warfare Center (NAWC) in West Trenton, New Jersey in 2009 in collaboration with TerraTherm, Inc., the Naval Facilities Engineering Services Center and the United States Geological Survey. The NAWC site was historically used as a jet engine testing facility from the mid-1950s to the late 1990s. During this time, the subsurface was contaminated with trichloroethylene (TCE) which was a common solvent used at the facility. The pilot test consisted of 15 heater/extraction wells installed to a depth of 16.8 m in weathered mudstone and operated for 102 days. Rock core samples were taken pre- and post-remediation to measure the initial TCE concentrations and evaluate the effect the TCH pilot test had. The data collected during the pilot test was used to create a two-dimensional (2D) finite difference model using TMVOC. TMVOC is part of the TOUGH 2 family of codes and is a numerical model that is capable of simulating multiphase flow, heat transfer and transport of volatile organic compounds in three-dimensional heterogenous porous media or fractured rock. The 2D model was used as a screening model to investigate TCE removal from the rock matrix when heating for 100 days with a similar heating pattern to what was employed at the NAWC site. The numerical domain incorporated three primary fractures with competent bedrock in between. As the test pilot was conducted in the weathered bedrock zone, a sensitivity analysis was first completed on the matrix permeability to help to match the TCE removal from the pilot test. The pilot test had a 63.5% removal of TCE from the study area compared to 67% from the baseline model. A limited sensitivity analysis was completed which investigated how the matrix porosity and rate of energy application would have on the success of TCE removal from the rock matrix. It revealed that the TCE removal increases with increased matrix porosity and increased rate of energy application. / Thesis (Master, Civil Engineering) -- Queen's University, 2013-01-02 22:32:05.274

In this thesis, I focused on numerical modelling of groundwater flow in the vicinity of groundwater circulation well (GCW). The thesis can be devided to two parts. In the first one, I created a simple numerical model of GCW. I used a cylindrical flow domain because of the radial symmetry of the problem. The task was to find out which parameters have the biggest influence on groundwater flow. It was found that the hydrogeological settings and hydraulic properties have more considerable effect on GW flow than the well construction parameters. Distance between the well screens is the only important construction parameter, other parameters can be neglected. However, we cannot neglect the influence of hydraulic properties of the porous medium. Considering the radius of influence of GCW, the presence of aquitards and anisotropy of layers affect the groundwater flow around the well seriously. These two parameters cause the extension of the radius of influence, which leads to a longer path of the particle of water. The travel time of particles increases too this slows down the remediation. A big influence has also an intensity of natural groundwater flow in the area because it decreases the radius of influence of the well. In the second part I created a numerical model of pilot site Velká Hleďsebe to investigate...

Mountain watersheds recently burned by wildfire often experience greater amounts of runoff and increased rates of sediment transport relative to similar unburned areas. Given the sedimentation and debris flow threats caused by increases in erosion, more work is needed to better understand the physical mechanisms responsible for the observed increase in sediment transport in burned environments and the time scale over which a heightened geomorphic response can be expected. In this study, we quantified the relative importance of different hillslope erosion mechanisms during two postwildfire rainstorms at a drainage basin in Southern California by combining terrestrial laser scanner-derived maps of topographic change, field measurements, and numerical modeling of overland flow and sediment transport. Numerous debris flows were initiated by runoff at our study area during a long-duration storm of relatively modest intensity. Despite the presence of a well-developed rill network, numerical model results suggest that the majority of eroded hillslope sediment during this long-duration rainstorm was transported by raindrop-induced sediment transport processes, highlighting the importance of raindrop-driven processes in supplying channels with potential debris flow material. We also used the numerical model to explore relationships between postwildfire storm characteristics, vegetation cover, soil infiltration capacity, and the total volume of eroded sediment from a synthetic hillslope for different end-member erosion regimes. This study adds to our understanding of sediment transport in steep, postwildfire landscapes and shows how data from field monitoring can be combined with numerical modeling of sediment transport to isolate the processes leading to increased erosion in burned areas.

Numerische Experimente wurden durchgeführt, um den Einfluß von Gittermaschenweite und subskaliger Heterogenität auf die Vorhersage der am Wasserkreislauf beteiligten Größen zu untersuchen. Die Modellergebnisse zeigen, daß die Evapotranspiration, Bewölkung und der Niederschlag von der Gittermaschenweite und der Heterogenität beeinflußt werden. Es zeigte sich, daß bei Verwendung gröberer Maschenweiten unter Einbezug der verschiedenen Landnutzungstypen innerhalb der Gittermasche die Obertlächenprozesse und Phänomene (z.B. Wärmeinseleffekt) realistischer beschrieben werden, als wenn nur ein Landnutzungstyp für das gesamte Gitterelement angenommen wird. / Numerical experiments were performed to investigate the influence of grid resolution and subgrid heterogeneity on the prediction of the quantities of the water cycle. The results were compared with each other and with those provided by a simulation using the same surface parameterization scheme but taking subgrid scale surface heterogeneity into account. The model results substantiate that the evapotranspiration, cloudiness and precipitation are affected by the grid resolution and the heterogeneity. lt was found that increasing the grid size but including the heterogeneity describes more realistically the surface processes and phenomena (e.g„ heat island effect) than assuming one land use type for the whole grid element.

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The hypoxic area in the Gulf of Mexico is the second largest in the world, which has received extensive scientific study and management interest. Previous modeling studies have concluded that the increased hypoxic area in the Gulf of Mexico was caused by the increased anthropogenic nitrogen loading of the Mississippi River; however, the nitrogen-area relationship is complicated by many other factors, such as wind, river discharge, and the ratio of Mississippi to Atchafalaya River flow. These factors are related to large-scale climate variability, and thus will not be affected by regional nitrogen reduction efforts. In the research presented here, both statistical (regression) and numerical models are used to study the influence of anthropogenic and climate factors on the hypoxic area variability in the Gulf of Mexico. The numerical model is a three-dimensional, coupled hydrological-biogeochemical model (ROMS-Fennel). Results include: (1) the west wind duration during the summer explain 55% of the hypoxic area variability since 1993. Combined wind duration and nitrogen loading explain over 70% of the variability, and combined wind duration and river discharge explain over 85% of the variability. (2) The numerical model captures the temporal variability, but overestimates the bottom oxygen concentrations. The model shows that the simulated hypoxic area is in agreement with the observations from the year 1991, as long as hypoxia is defined as oxygen concentrations below 3 mg/L rather than below 2 mg/L. (3) The first three modes from an Empirical Orthogonal Function (EOF) analysis of the numerical model output results explain 62%, 8.1% and 4.9% of the variability of the hypoxic area. The Principle Component time series is cross-correlated with wind, dissolved inorganic nitrogen concentration and river discharge. (4) Scenario experiments with the same nitrogen loading, but different duration of upwelling favorable wind, indicate that the upwelling favorable wind is important for hypoxic area development. However, a long duration of upwelling wind decreases the area. (5) Scenario experiments with the same nitrogen loading, but different discharges, indicate that increasing river discharge by 50% increases the area by 42%. Additionally, scenario experiments with the same river discharge, but different nitrogen concentrations, indicate that reducing the nitrogen concentration by 50% decreases the area by 75%. (6) Scenario experiments with the same nitrogen loading, but different flow diver- sions, indicate that if the Atchafalaya River discharges increased to 66.7%, the total hypoxic area increases the hypoxic area by 30%, and most of the hypoxic area moved from east to west Louisiana shelf. Additionally, if the Atchafalaya River discharge decreased to zero, the total hypoxic area increases by 13%. (7) Scenario experiments with the same nitrogen loading, but different nitrogen forms, indicate that if all the nitrogen was in the inorganic forms, the hypoxic area increases by 15%. These results have multiple implications for understanding the mechanisms that control the oxygen dynamics, reevaluating management strategies, and improving the observational methods.