Rodrigo Cienfuegos

Sea state is a key variable in ocean and coastal dynamics. The sea state is either sparsely measured by wave buoys and satellites or modelled over large scales. Only a few attempts have been devoted to sea state measurements covering a large domain; in particular its estimation from optical images. With optical technologies becoming omnipresent, optical images offer incomparable spatial resolution from diverse sensors such as shore-based cameras, airborne drones (unmanned aerial vehicles/UAVs), or satellites. Here, we present a standalone methodology to derive the water surface elevation anomaly induced by wind-generated ocean waves from optical imagery. The methodology was tested on drone and satellite images and compared against ground truth. The results show a clear dependence on the relative azimuth view angle in relation to the wave crest. A simple correction is proposed to overcome this bias. Overall, the presented methodology offers a practical way of estimating ocean waves f...

Due to Chile’s notorious and frequent seismic activity, earthquake- and tsunami-related studies have become a priority in the interest of developing effective countermeasures to mitigate their impacts and to improve the country’s resilience. Mitigation measures are key to accomplish these objectives. Therefore, this investigation adopts a tsunami damage assessment framework to evaluate the direct benefits of tsunami mitigation works implemented by the Chilean government in the town of Dichato in the aftermath of the 2010 tsunami. We perform an ex post analysis of the potential damage reduction produced by these works studying what would have been the consequences on the built environment if they were in place for the tsunami that hit this area after the Maule earthquake in February 27, 2010. We use state-of-the-art tsunami simulation models at high resolution to assess the reduction in tsunami intensity measures, which serve as input to evaluate the benefit from averted damage again...

Multi-hazard evaluations are fundamental inputs for disaster risk management plans and the implementation of resilient urban environments, adapted to extreme natural events. Risk assessments from natural hazards have been typically restricted to the analysis of single hazards or focused on the vulnerability of specific targets, which might result in an underestimation of the risk level. This study presents a practical and effective methodology applied to two Chilean coastal cities to characterize risk in data-poor regions, which integrates multi-hazard and multi-vulnerability analyses through physically-based models and easily accessible data. A matrix approach was used to cross the degree of exposure to floods, landslides, tsunamis, and earthquakes hazards, and two dimensions of vulnerability (physical, socio-economical). This information is used to provide the guidelines to lead the development of resilience thinking and disaster risk management in Chile years after the major and ...

Wave breaking is one of the main forcing mechanisms in coastal hydrodynamics, driving mean water levels and currents. Understanding its behavior is key in the goal of improving our comprehension of coastal morphodynamics variations. One way to improve our understanding is through the use of numerical models, such as phase-resolving numerical models based on the Boussinesq equations (Kirby, 2016), which are modified to include breaking by the inclusion of a breaking criteria and a dissipation mechanism. Since there is not a universal law capable of characterizing the wave breaking, the existing models must be calibrated. Traditionally, this is done by adjusting wave height profiles and other free surface statistical parameters without explicitly considering the time-space location and duration of the breaking process. Consequently, it is possible to calibrate a model that accurately represents wave elevation statistics parameters, such as wave height and wave set-up; however, it migh...

Dans ce travail nous developpons un modele numerique de propagation de houle base sur les equations faiblement dispersives de la famille de Boussinesq (Serre). Un schema aux volumes finis de 4eme ordre qui utilise une reconstruction compacte des flux aux interfaces est propose afin d'integrer dans le temps et l'espace les equations de Serre. Le modele mathematique permet une description de la propagation d'ondes de gravite pour des ecoulements a surface libre a forte courbure sur un profil de plage quelconque depuis des profondeurs intermediaires et jusqu'au trait de cote. Par ailleurs, nous decrivons l'implementation de conditions aux limites permettant la representation du mouvement de jet de rive pres du trait de cote, l'absorption et generation d'ondes au large, ainsi que la reflexion totale sur une paroi verticale. Dans la seconde partie de la these, la problematique du deferlement induit par les variations bathymetriques est abordee. La theorie des chocs dans le cadre des equations de l'eau peu profonde, ainsi que le concept de rouleau de deferlement tel qu'il a ete introduit par Svendsen en 1984, fournissent les elements necessaires au developpement d'une nouvelle parametrisation du phenomene. Cette approche utilise un modele de type couche de melange, a la fois dans l'equation de continuite (transfert local de masse et d'energie potentielle) et de conservation de la quantite de mouvement (deficit local de QOM), afin de prendre en compte la dissipation d'energie et reproduire en meme temps les asymetries horizontales et verticales des vagues. Le modele de propagation de houle ainsi obtenu est valide a l'aide de nombreuses experiences en laboratoire.

On April 1st2014 a 8.1 Mw Earthquake occurred at 23:46:50 UTC (20:46:50 local time) with its epicenter located off the coast of Pisagua, 68 km north of the city of Iquique (An et al., 2014). The potential risk of earthquake and tsunami in this area was widely recognized by the scientific community (Chlieh et al., 2004). Nevertheless, the energy released by this earthquake and the associated slip distribution was much less than expected. In the present contribution, we will reassess the tsunami hazard for the North of Chile taking into account the occurrence of the recent events, focusing on the potential impact that a worse case scenario could produce in the city of Iquique. For that purpose, an updated tsunami source will be derived using updated information on the seismic and co-seismic tectonic displacements that is available from historical, geological information, and the dense GPS and seismometer networks available in the North of Chile. The updated tsunami source will be used...

ABSTRACT On April 1st, 2014, an earthquake with moment magnitude Mw 8.2 occurred off the coast of northern Chile, generating a tsunami that prompted evacuation along the Chilean coast. Here, tsunami characteristics are analyzed through a combination of field data and numerical modeling. Despite the earthquake magnitude, the tsunami was moderate, with a relatively uniform distribution of runup, which peaked at 4.6 m. This is explained by a concentrated maximal slip at intermediate depth on the megathrust, resulting in a rapid decay of tsunami energy. The tsunami temporal evolution varied, with locations showing sustained tsunami energy, while others showed increased tsunami energy at different times after the earthquake. These are the result of the interaction of long period standing oscillations and trapped edge wave activity controlled by inner shelf slopes. Understaing these processes is relevant for the region, which still posses a significant tsunamigenic potential.

ABSTRACT On 27 February, 2010 a magnitude Mw 8.8 earthquake occurred off the coast of Chile's Maule region some 100 km N of Concepción, causing substantial damage and loss of life on Chile's mainland and the Juan Fernandez archipelago. The majority of the 521 fatalities are attributed to the earthquake, while the tsunami accounts for 124 victims. Fortunately, ancestral knowledge from past tsunamis such as the giant 1960 event, as well as tsunami education and evacuation exercises prompted most coastal residents to spontaneously evacuate to high ground after the earthquake. The majority of the tsunami victims were tourists staying overnight in low lying camp grounds along the coast. A multi-disciplinary international tsunami survey team (ITST) was deployed within days of the event to document flow depths, runup heights, inundation distances, sediment deposition, damage patterns at various scales, performance of the man-made infrastructure and impact on the natural environment. The 3 to 25 March ITST covered an 800 km stretch of coastline from Quintero to Mehuín in various subgroups the Pacific Islands of Santa María, Juan Fernández Archipelago, and Rapa Nui (Easter), while Mocha Island was surveyed 21 to 23 May, 2010. The collected survey data includes more than 400 tsunami runup and flow depth measurements. The tsunami impact peaked with a localized maximum runup of 29 m on a coastal bluff at Constitución and 23 m on marine terraces on Mocha Island. A significant variation in tsunami impact was observed along Chile's mainland both at local and regional scales. Inundation and damage also occurred several kilometres inland along rivers. Eyewitness tsunami videos are analysed and flooding velocities presented. Observations from the Chile tsunami are compared against the 1960 Chile, 2004 Indian Ocean and 2011 Tohoku Japan tsunamis. The tsunamigenic seafloor displacements were partially characterized based on coastal uplift measurements along a 100 km stretch of coastline between Caleta Chome and Punta Morguilla. More than 2 m vertical uplift were measured on Santa Maria Island. Tsunami propagation in the Pacific Ocean is simulated using the benchmarked tsunami model MOST (Titov and Gonzalez, 1997; Titov and Synolakis, 1998). For initial conditions the inversion model of Lorito et al. (2011) is utilized. The model results highlight the directivity of the highest tsunami waves towards Juan Fernández and Easter Island during the transoceanic propagation. The team interviewed numerous eyewitnesses and educated residents about tsunami hazards since community-based education and awareness programs are essential to save lives in locales at risk from locally generated tsunamis.

Dans ce travail nous developpons un modele numerique de propagation de houle base sur les equations faiblement dispersives de la famille de Boussinesq (Serre). Un schema aux volumes finis de 4eme ordre qui utilise une reconstruction compacte des flux aux interfaces est propose afin d'integrer dans le temps et l'espace les equations de Serre. Le modele mathematique permet une description de la propagation d'ondes de gravite pour des ecoulements a surface libre a forte courbure sur un profil de plage quelconque depuis des profondeurs intermediaires et jusqu'au trait de cote. Par ailleurs, nous decrivons l'implementation de conditions aux limites permettant la representation du mouvement de jet de rive pres du trait de cote, l'absorption et generation d'ondes au large, ainsi que la reflexion totale sur une paroi verticale. Dans la seconde partie de la these, la problematique du deferlement induit par les variations bathymetriques est abordee. La theorie des chocs dans le cadre des equations de l'eau peu profonde, ainsi que le concept de rouleau de deferlement tel qu'il a ete introduit par Svendsen en 1984, fournissent les elements necessaires au developpement d'une nouvelle parametrisation du phenomene. Cette approche utilise un modele de type couche de melange, a la fois dans l'equation de continuite (transfert local de masse et d'energie potentielle) et de conservation de la quantite de mouvement (deficit local de QOM), afin de prendre en compte la dissipation d'energie et reproduire en meme temps les asymetries horizontales et verticales des vagues. Le modele de propagation de houle ainsi obtenu est valide a l'aide de nombreuses experiences en laboratoire.

ABSTRACT The ensuing tsunami from the Mw=8.8 2010 Chilean earthquake was one of the most destructive events on Chilean history (Fritz et al. 2011). It caused not only major damage and loss of infrastructure on several locations, but also drastic morphological changes on coastal environments (Cienfuegos et al., 2010). The large scale and magnitude of the change could be considered effectively as system resets. This situation presented a unique opportunity to witness the natural recovery of some coastal landforms such as sand spits. The Mataquito River mouth, located just in front of the rupture area where most of the earthquake energy was released (Lay et al. 2010), is an example of a natural coastal system heavily affected by the 2010 tsunami: its 8 km-long sand spit almost completely disappeared under the combined action of tsunami waves and the relatively large land subsidence (Vargas et al. 2011). After the earthquake and tsunami, we have monitored the coastal evolution of the river mouth using different techniques such as site surveys, airborne and satellite images, to characterize qualitatively and identify the main processes driving the formation and recovery of the sand spit by waves and wind. This was complemented with forcing information like wind, waves and river discharge in order to better understand the system dynamics. Our observations evidenced a massive accretion and a surprisingly fast coastal recovery . In fact, most of the original configuration of the spit was reformed in less than 18 months. On the contrary, Duao beach, located 15 km north of Mataquito, experienced a dramatic erosion probably by land subsidence and consequent beach response to incoming wave climate. In this work we discuss on the role of waves, longshore currents, river hydrology and land subsidence in determining the rapid coastal evolution experienced in the Mataquito area. Moreover, this ongoing research will adress whether morphological changes are definitive or not. References Cienfuegos et al. 2010. "Observations on morphological changes by the impact of the February 27, 2010 tsunami along the coastline of V-VI-VII Regions". AGU Chapman Conference on Giant Earthquakes and Their Tsunamis, Viña del Mar, Chile. Fritz et al. 2011. "Field Survey of the 27 February 2010 Tsunami, Chile". Pure and Applied Geophysics, 2011. doi:10.1007/s00024- 011-0283-5. Lay et al. 2010. "Teleseismic inversion for rupture process of the 27 February 2010 Chile earthquake". Geophysical Research Letters, 37, L13301, doi:10.1029/2010GL043379.

ABSTRACT Tsunamis hit humans and coastal landscapes causing casualties, economical losses, environmental, and morphological changes. On February 27 th 2010, Chile suffered one of the worst earthquake and tsunamis that ever hit his coast with significant consequences in human lives and infrastructure. In terms of coastal landforms, several river mouths and beaches were affected, and co-seismic displacements produced subsidence and uplift in different areas. The Mataquito River mouth and the Duao beach, located in the Maule region few kilometers away from each other, are two examples of coastal systems that were differently impacted by tsunami waves and land subsidence. While a large sand spit present in the river mouth almost disappeared under the combined action of subsidence and tsunami currents, Duao beach was barely impacted by the event. In this paper we study the post-tsunami evolution process and the different morphological changes they have experienced since February 2010. Our findings confirm that the footprint of an earthquake/tsunami is very much influenced by local hydro-climatic forcings and co-seismic land level changes. Over these last three years, both systems have evolved rapidly to configurations that differ from the ones they had prior to the earthquake and tsunami. Keywords , beach and river mouth morphodynamics,

This paper presents a new depth inversion methodology from video imagery. The strength of the method is the use of a fully non-linear Boussinesq wave model in combination with a very complete video-derived laboratory wave observation that includes period, celerity and wave height. Compared to the previous use of wave dispersion formulas, here the better description of wave dynamics substantially improves bathymetry estimation. For the considered laboratory case, error on bathymetry is as small as 8 % whereas other formulations, shallow water or non-linear derived solution can only attain 24 % and 14 %, respectively. More in-depth analysis on the error shows a fair sensitivity on video-derived breaker height and describes the large contribution of nonlinearities. The recent possibility of using Serre's dispersion relation in combination with video-derived wave height provides a reasonable performance and should be further envisaged for one-dimensional depth inversion. Future extensions of this work involve the use of a two-dimensional Boussinesq model to include more hydrodynamics processes such as wave-driven circulation over three-dimensional surfzone sandbars.

We present experimental and numerical analysis of nonlinear processes responsible for generating infragravity waves in the nearshore. We provide new experimental data on random wave propagation and associated velocity profiles in the shoaling and surf zones of a very mild slope beach. We analyze low frequency wave generation mechanisms and dynamics along the beach and examine in detail the ability of the fully nonlinear Boussinesq- type model SERR1D (Cienfuegos et al., 2010) to reproduce the complex dynamics of high frequency wave propagation and energy transfer mechanisms that enhance infragravity wave generation in the laboratory.

On February 27, 2010, a magnitude M= 8.8 earthquake occurred off the coast of Chile's Maule region causing substantial damage and loss of life. Ancestral tsunami knowledge from the 1960 event combined with education and evacuation exercises prompted most ...

A conceptual analysis of the coupling between bars and infragravity waves is performed combining laboratory experiments and numerical modeling. Experiments are carried out in a wave flume with a barred profile. The Boussinesq fully-nonlinear model SERR1D is validated with the laboratory data and a sensitivity analysis is performed next to study the influence on the infragravity wave dynamics of bar amplitude and location, and swash zone slope. A novel technique of incident and reflected motions separation that conserves temporal characteristics is applied. We observe that changing bar characteristics induces substantial variations in trapped energy. Interestingly, a modification of swash zone slope has a large influence on the reflected component, controlling amplitude and phase time-lag, and consequently on the resonant pattern. Variations of trapped infragravity energy induced by changes of swash zone slope reach 25 %. These changes in infragravity pattern consequently affect shor...

A non-uniform alongshore wave forcing on an experimental uneven mobile bathymetry create mean circulation on a rip channel. A 2D numerical hydrodynamic model that integrates the non-linear shallow-water equations in a shock-capturing finite-volume framework is used to validate the nearshore circulation, and drifters displacement.

Enhancing the performance of clarifiers requires a thorough understanding of their hydraulics. Fluorescence spectroscopy and acoustic doppler velocimeter (ADV) profiling generally have been used separately to evaluate secondary settlers. We propose that simultaneous use of these techniques is needed to obtain a more reliable and useful evaluation. Experiments were performed on laboratory- and full-scale clarifiers. Factors affecting Fluorescein and Rhodamine 6G properties were identified. Underestimations up to 500% in fluorescence intensities may be derived from differential fluorescence quenching by oxygen. A careful control and interpretation of fluorescent dye experiments is needed to minimize artifacts in real settings. While flow-curve tests constructed under controlled conditions provided a more accurate overall quantitative estimation of the hydraulic performance, ADV velocity and turbulence profiling provided a detailed spatial understanding of flow patterns that was used to troubleshoot and fix the causes of hydraulic short-circuits.

On 27 February 2010, a magnitude M w = 8.8 earthquake occurred off the coast of Chile’s Maule region causing substantial damage and loss of life. Ancestral tsunami knowledge from the 1960 event combined with education and evacuation exercises prompted most coastal residents to spontaneously evacuate after the earthquake. Many of the tsunami victims were tourists in coastal campgrounds. The international tsunami survey team (ITST) was deployed within days of the event and surveyed 800 km of coastline from Quintero to Mehuín and the Pacific Islands of Santa María, Mocha, Juan Fernández Archipelago, and Rapa Nui (Easter). The collected survey data include more than 400 tsunami flow depth, runup and coastal uplift measurements. The tsunami peaked with a localized runup of 29 m on a coastal bluff at Constitución. The observed runup distributions exhibit significant variations on local and regional scales. Observations from the 2010 and 1960 Chile tsunamis are compared.