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Physical modeling studies have endeavored to quantify the influence of plant biophysical parameters and hydrodynamics on wave-vegetation interactions and coastal protection. The accuracy with which such studies have characterized stem motion is limited by the predominant use of plant surrogates, and the few saltmarsh species considered in live vegetation studies. To address this, prototype-scale experiments were conducted in the outdoor Large Wave Canal of the Institut National de la Recherche Scientifique, Québec, in collaboration with the University of Ottawa and the National Research Council Canada, allowing novel characterization of live vegetation deformation under wave action. Two saltmarsh species were investigated (Spartina alterniflora, Spartina patens) under various irregular wave conditions (0.03 m< Hs Ts ≈ 2.5, 10 s). Stem deformation was characterized using submerged cameras and bending angle tracking, coupled with wave height and velocity measurements. Significant differences in stem flexibility were observed between species, with S. alterniflora exhibiting more rigid stems (EIalterniflora=0.051 Nm2) than S. patens (EIpatens=0.0015 Nm2; t-test; p

Extreme hydrodynamic events, such as tsunamis, can transport debris of a very wide range of dimensions, from cohesive sediments to debris such as trees and cars. Large sized floating debris are particularly hazardous for two main reasons: (i) they can accumulate in narrow passages, such as the case of log jams at bridges, and obstruct the flow, creating potential for further flooding; (ii) they can impact directly on structures transferring significant energy to them, due to their mass and velocity, which can lead to damage and even failure. The transport and the interactions of this type of debris is studied experimentally, often in the context of tsunamis and flash floods. However, numerical studies on large floating debris impact on structures are rare. Therefore, the present study aims to address this gap by numerically modelling of the flow-debris-structure interactions. First, the experiments of Stolle et al. (2018) are simulated numerically. These experiments involve a single positively buoyant container impact a structure as a result of being transported by a dam-break flow. The numerical simulations are carried using the open source DualSPHysics model based on the Smoothed Particle Hydrodynamics method. First, the hydrodynamics results were validated with data from Stolle et al. (2018). Subsequently, DualSPHysics was coupled with the Multiphysics engine CHRONO to simulate the container and its impact on the structure. The dam break event described in Stolle et al. (2018), was generated by modelling the movement of a swing gate using the experimental time series, with the container and the structure positioned at 3.2 m and 7.03 m, respectively, downstream of the reservoir consistently with Stolle et al. (2018). The trajectory as well as the velocity of the centroid of the container were tracked throughout the simulation. The agreement between the model and the experiment results is quantitatively assessed and it is shown that the model is accurate in reproducing the floating container trajectory, impact velocity and, in turn, force. In a second stage, numerical simulations beyond the conditions tested by Stolle et al. (2018) are used to investigate the role of the flow velocity, impact angle and location.

Permafrost coastlines represent a large portion of the world&rsquo, s coastal area and these areas have become increasingly vulnerable in the face of climate change. The predominant mechanism of coastal erosion in these areas has been identified through several observational studies as thermomechanical erosion&mdash, a joint removal of sediment through the melting of interstitial ice (thermal energy) and abrasion from incoming waves (mechanical energy). However, further developments are needed looking how common design parameters in coastal engineering (such as wave height, period, sediment size, etc.) contribute to the process. This paper presents the current state of the art with the objective of establishing the necessary research background to develop a process-based approach to predicting permafrost erosion. To that end, an overarching framework is presented that includes all major, erosion-relevant processes, while delineating means to accomplish permafrost modelling in experimental studies. Preliminary modelling of generations zero and one models, within this novel framework, was also performed to allow for early conclusions as to how well permafrost erosion can currently be modelled without more sophisticated setups.

Coastal areas are often important to economic, social, and environmental processes throughout the world. With changing climate and growing populations in these areas, coastal communities have become increasingly vulnerable to extreme flooding events, such as tsunami, storm surges, and flash floods. Within this new paradigm, there has been an effort to improve upon current methods of hazard assessment, particularly for tsunami. Recently, the American Society of Civil Engineers (ASCE) released the ASCE 7 Chapter 6 which was the world’s first standard, written in mandatory language, that addressed tsunami resilient design in a probabilistic manner for several of its prescriptions. While often the focus tends to be on mapping the hazards related to hydraulic loading conditions, post-tsunami field surveys from disaster-stricken coastal communities have also shown the importance of also considering the loads exerted by solid objects entrained within the inundating flows, commonly referred to as debris loading. Limited research has addressed debris hazard assessment in a comprehensive manner. Debris loading can be generally divided into two categories: impact and damming. Debris impact loads are caused by the rapid strike of solid objects against a structure. Debris damming loads are the result of the accumulation of debris at the face of or around a structure, causing thus an obstruction to the flow. The primary difference between these loads is the time period over which they act. The rapid loading due to debris impacts requires structural properties be considered in assessing the associated loads whereas debris damming loads are generally considered in a quasi-static manner. In assessing the hazard associated with both impact and damming loading conditions, methodologies must be developed to consider the likelihood of the load occurring and the magnitude of that load. The primary objective of this thesis was to develop a probabilistic framework for assessing debris hazards in extreme coastal flooding events. To achieve this objective, the components of the framework were split into three general categories: debris transport, debris damming, and debris impact. Several physical experimental studies were performed to address each of these components, representing the most comprehensive assessment of debris hazards in extreme flooding events to date., Küstengebiete auf der ganzen Welt sind oftmals wichtig für wirtschaftliche, soziale und ökologische Prozesse. Aufgrund des sich ändernden Klimas und der wachsenden Bevölkerung in diesen Gebieten sind Küstengemeinden zunehmend anfällig für extreme Überschwemmungen durch Tsunami, Sturmfluten und Sturzfluten. Innerhalb dieses neuen Paradigmas wurden Anstrengungen unternommen, um die derzeitigen Methoden zur Gefährdungsbeurteilung, insbesondere für Tsunami, zu verbessern. Die American Society of Civil Engineers (ASCE) veröffentlichte das ASCE 7 Chapter 6, den weltweit ersten verbindlichen Standard, der sich in mehreren seiner Vorschriften mit einem probabilistischen Ansatz mit tsunami-beständiger Konstruktion befasst. Während der Schwerpunkt häufig auf der Erfassung der Gefahren im Zusammenhang mit hydraulischen Belastungszuständen liegt, haben Felduntersuchungen in von Tsunami getroffenen Küstengebieten gezeigt, dass es wichtig ist, auch die Belastungen zu berücksichtigen, die von festen Gegenständen ausgehen, die im einströmenden Wasser als Treibgut mitgeführt werden. Umfassende Forschung zur Gefährdungsbeurteilung von Treibgut ist nur begrenzt vorhanden. Die Belastung durch Treibgut kann im Allgemeinen in zwei Kategorien unterteilt werden: Aufprall und Aufstau. Lasten aus dem Aufprall des Treibgutes werden durch das schnelle Auftreffen fester Gegenstände auf eine Struktur verursacht. Lasten aus dem Aufstauen sind das Ergebnis der Akkumulation von Treibgut an der Oberfläche oder um eine Struktur herum, was zu einer Behinderung der Strömung führt. Der Hauptunterschied zwischen diesen Lasten ist der Zeitraum, über den sie wirken. Die schnelle Belastung durch den Aufprall von Treibgut erfordert, dass bei der Beurteilung der damit verbundenen Belastungen strukturelle Eigenschaften berücksichtigt werden, wohingegen Lasten aus dem Aufstauen von Treibgut im Allgemeinen quasi-statisch berücksichtigt werden. Für die Bewertung der Gefährdung, die sowohl mit dem Aufprall als auch mit dem Aufstauen verbunden ist, müssen Methoden entwickelt werden, um die Wahrscheinlichkeit des Auftretens der Last und die Größe dieser Last zu berücksichtigen. Das Hauptziel der Dissertation war die Entwicklung eines probabilistischen Ansatzes zur Bewertung der Gefährdung durch Treibgut bei extremen Überflutungsereignissen an der Küste. Um dieses Ziel zu erreichen, wurden die Komponenten des Rahmens in drei allgemeine Kategorien unterteilt: Transport, Aufstau und Aufprall von Treibgut. Um jede dieser Komponenten zu untersuchen, wurden mehrere physikalisch-experimentelle Studien durchgeführt, die die bislang umfassendste Beurteilung der Gefährdung durch Treibgut bei extremen Überschwemmungen darstellen.

Presented at: Coastal Structures Conference 2019, Hannover, Germany, September 30th – October 2nd, 2019

This study investigates two gate devices which impound a volume of water, whose sudden release generates a dam-break wave. The aim is to identify the reciprocal interaction between the gate motion and the released volume of water. For the first time, lift gates and swing gates are systematically studied and compared. The influence by the opening of the gate on the evolving bore is related to the opening time. The overall objective of this study is to provide guidance as to how fast swing and lift gates need to open to effectively limit adverse effects on the formation of the dam-break wave. For this study, numerical simulations are conducted using the Smoothed Particle Hydrodynamics (SPH) formulation. The open source code DualSPHysics is used herein (Crespo et al., 2015). A calibrated setup is used to systematically investigate a large number of setups comprising constantly-accelerated lift gates and swing gates opening with constant angular velocities. To match opening procedures of existing test facilities, the distance from the gate edges to the bottom of the flume is a quadratic function in time, anticipating electrically- or gravity-driven gate concepts. Based on the analysis of the time-history of the water surface elevation, a more detailed criterion for acceptable opening times for both, swing and lift gates is provided. A comparison with existing guidance on minimum opening times for lift gates is also provided; moreover, the updated opening criteria is valid for the entire section downstream of the gates. The use of the updated opening diagrams allows to determine minimum opening times for future experimentation.

Tsunamis are among the most devastating and complex natural disasters, affecting coastal regions worldwide. Tsunami waves are generated through many natural phenomena, such as earthquakes, landslides, and volcanic eruptions. The waves travel at high speeds away from the source, potentially affecting multiple countries with very little warning. Over the past several decades, tsunamis such as the 2004 Indian Ocean, the 2010 Chilean, and the 2011 Tohoku Tsunami served as reminders of the potential devastation of these natural disasters, resulting in tragic loss of life and billions of dollars in damages. Forensic engineering field investigations and subsequent analysis of these events have demonstrated that infrastructure in these tsunami-prone regions was not adequately prepared for the extreme forces associated with a tsunami. As a result, there has been an increased research emphasis worldwide on the planning and design of infrastructure located in tsunami-prone areas to be better prepared for such future events. The present study aims to experimentally investigate and analyze the motion of debris carried by an inundating tsunami flood. One of the previous challenges involved in the evaluation of debris motion during such events was a lack of experimental methods that could non-invasively, quickly and accurately track the motion of debris at high velocities. This study introduces two innovative methods of tracking the debris. The first one used a novel camera-based tracking algorithm, while the second used Bluetooth and Inertial Measurement Unit sensors to track the debris within the inundating tsunami flood. The study outlines, for the first time, the technology and methods involved in the two tracking methods as it used both dry-test and wet-test experiments to evaluate the applicability of these methods in coastal and hydraulic engineering. This study used these two methods to evaluate the motion of debris from experiments conducted in a new Tsunami Wave Basin commissioned recently at Waseda University (Tokyo, Japan). The study examined the effect of the initial positioning of the debris, particularly focusing on the spreading area of the debris (determining thus their maximum displacement and the spreading angle of the debris). The results showed that an increase in the number of the debris resulted in an increase in the spreading angle of the debris and a decrease in the displacement of the debris. The increased number of debris also added significantly more variation in the final resting position of the debris due to the increased debris-debris collisions. The initial orientation of the debris also affected debris motion, particularly influencing the peak velocity of the debris and the distance from the initial debris resting position to where the peak velocity was observed.