Research Outputs
Land cover and potential for tsunami evacuation in rapidly growing urban areas. The case of Boca Sur (San Pedro de la Paz, Chile)
The destructive potential of a massive tsunami is not only related to society’s response capacity and evacuation plans, but also to the urban morphology and land cover. The Boca Sur neigh- borhood is one of the areas in central Chile that is most exposed to tsunamis, and it is framed in the context of increasing urban growth. Faced with the worst tsunami scenario (earthquake Mw = 9.0), residents’ evacuation potential is analyzed by using a least-cost-distance model, and two scenarios of land cover change are considered (2002 and 2018). Presently, the sector’s urban areas have grown by 83%, therefore its population has also grown. The evacuation times consider an average walking speed (1.22 m/s) for both years (2002 and 2018). This analysis establishes that over 40% of the study area is more than 60 min away from the safe zones established by authorities. This differs greatly from the 22-min average tsunami arrival time. Moreover, 19% of the area could not be evacuated in less than 30 min. Therefore, it can be concluded that the increased urbanization in the coastal area has not improved travel times, as urban planning did not consider the optimization of evacuation times to the designated safe zones. In this study, we propose new safe zones that would help reducing evacuation times to 30 min. In addition to the area’s high tsunami risk, the evacuated population’s strong travel time limitations are added, prioritizing the incorporation of social and urban resilience elements that help to effectively reduce the risk of disaster, by using land-use planning and community work.
Comparative analysis of tsunami recovery strategies in small communities in Japan and Chile
The Sendai Framework for Disaster Risk Reduction emphasizes the need to rebuild better after a disaster to ensure that the at-risk communities can withstand a similar or stronger shock in the future. In the present work, the authors analyzed the reconstruction paths through a comparative analysis of the perspective of a community in Japan and another in Chile, and their respective local governments. While both countries are at risk to tsunamis, they follow different reconstruction philosophies. Data was gathered through key informant interviews of community members and local government officials, by adapting and modifying the Building Resilience to Adapt to Climate Extremes and Disasters (BRACED) 3As framework to a tsunami scenario. The 3As represent anticipatory, adaptive, and absorptive capacities as well as transformative capacities and respondents were asked to rate this according to their perspectives. It was found that while both communities perceive that much is to be done in recovery, Kirikiri has a more holistic and similar perspective of the recovery with their government officials as compared to Dichato. This shows that community reconstruction and recovery from a disaster requires a holistic participation and understanding.
Damage assessment of the May 31st, 2019, Talcahuano tornado, Chile
On May 31st, 2019, a tornado hit the city of Talcahuano, Chile, generating significant damage to structures and leaving one person dead. The objective of the present paper is to report on damage to structures in Talcahuano. A preliminary survey was performed by the Municipality of Talcahuano and covered the entire affected area with a cellphone web application used to report the severity and distribution of damage. A more comprehensive damage survey was conducted in the Brisa del Sol neighborhood in the Medio Camino area by the UCSC team to assess the damage distribution within an area with well-defined and homogeneous building typologies. The results of the field surveys showed that the tornado behaved as a skipping tornado and that most damage to houses consisted of wall opening damage, roof sheathing failure, and wall cover removal (EF0), followed by partial roof removal(EF1). It was noticeable that self-built systems (house additions) were more damaged than original houses, which may be explained by the fact that such structures do not always meet minimum building standards. It is recommended that field surveys conducted by municipalities and the Ministry of Social Development considertypical damage types rather than just categories such as minor, moderate, or major. Finally, it is recommendedthat the feasibility of implementing mitigation measures such as stricter wind load provisions and dual-objective tornado design philosophy in the Concepci´on-Talcahuano area be analyzed.
Development and application of a tsunami fragility curve of the 2015 tsunami in Coquimbo, Chile
The last earthquake that affected the city of Coquimbo took place in September 2015 and had a magnitude of Mw=8.3, resulting in localized damage in low-lying areas of the city. In addition, another seismic gap north of the 2015 earthquake rupture area has been identified; therefore, a significant earthquake (Mw=8.2 to 8.5) and tsunami could occur in the near future. The present paper develops a tsunami fragility curve for the city of Coquimbo based on field survey data and tsunami numerical simulations. The inundation depth of the 2015 Chile tsunami in Coquimbo was estimated by means of numerical simulation with the Non-hydrostatic Evolution of Ocean WAVEs (NEOWAVE) model and five nested grids with a maximum grid resolution of 10 m. The fragility curve exhibited behavior similar to that of other curves in flat areas in Japan, where little damage was observed at relatively high inundation depths. In addition, it was observed that Coquimbo experienced less damage than Dichato (Chile); in fact, at an inundation depth of 2 m, Dichato had a ∼75 % probability of damage, while Coquimbo proved to have only a 20 % probability. The new fragility curve was used to estimate the damage by possible future tsunamis in the area. The damage assessment showed that ∼50 % of the structures in the low-lying area of Coquimbo have a high probability of damage in the case of a tsunami generated off the coast of the study area if the city is rebuilt with the same types of structures.
Riesgo de tsunami y planificación resiliente de la costa chilena: La localidad de Boca Sur, San Pedro de la Paz (37° S)
Se evalúa el riesgo de inundación por tsunami en la localidad de Boca Sur, comuna de San Pedro de La Paz (37ºS), Región del Biobío. Se consideró un escenario extremo de tsunami generado por un sismo de magnitud Mw= 9.0. La inundación por tsunami se obtuvo mediante modelación numérica usando el código NEOWAVE con 4 mallas anidadas de diferente resolución espacial y topo-batimetría de detalle. El análisis de vulnerabilidad consideró las dimensiones física, socioeconómica y organizacional, con datos obtenidos a través del Instituto Nacional de Estadística a nivel de manzana censal y encuestas a la población. Se determinó que el primer tren de ondas llega a la costa luego de 22 minutos de ocurrido el terremoto, alcanzando la cota de 5 msnm y alturas de fl ujo de hasta 2 m. Los factores de vulnerabilidad que explican el riesgo se asociaron a una alta precariedad de la vivienda, bajo nivel de bienestar social, alta densidad poblacional y bajo nivel de organización comunitaria de la población en caso de evacuación frente a tsunamis.
Vulnerability of physical infrastructure network components to damage from the 2015 Illapel Tsunami, Coquimbo, Chile
This study assesses physical infrastructure vulnerability for infrastructure network components exposed during the 2015 Illapel tsunami in Coquimbo, Chile. We analyse road and utility pole vulnerability to damage, based on interpolated and simulated tsunami hazard intensity (flow depth, flow velocity, hydrodynamic force and momentum flux) and network component characteristics. A Random Forest Model and Spearman’s Rank correlation test are applied to analyse variable importance and monotonic relationships, with respect to damage, between tsunami hazards and network component attributes. These models and tests reveal that flow depth correlates higher with damage, relative to flow velocity, hydrodynamic force and momentum flux. Scour (for roads and utility poles) and debris strikes (for utility poles) are strongly correlated with damage. A cumulative link model methodology is used to fit fragility curves. These fragility curves reveal that, in response to flow depth, Coquimbo roads have higher vulnerability than those analysed in previous tsunami event studies, while utility poles demonstrate lower vulnerability than with previous studies. Although we identify tsunami flow depth as the most important hydrodynamic hazard intensity metric, for causing road and utility pole damage, multiple characteristics correlate with damage and should also be considered when classifying infrastructure damage levels.
Risk factors and perceived restoration in a town destroyed by the 2010 Chile tsunami
A large earthquake and tsunami took place in February 2010, affecting a significant part of the Chilean coast (Maule earthquake, Mw of 8.8). Dichato (37° S), a small town located on Coliumo Bay, was one of the most devastated coastal areas and is currently under reconstruction. Therefore, the objective of this research is to analyze the risk factors that explain the disaster in 2010, as well as perceived restoration 6 years after the event. Numerical modeling of the 2010 Chile tsunami with four nested grids was applied to estimate the hazard. Physical, socioeconomic and educational dimensions of vulnerability were analyzed for pre- and post-disaster conditions. A perceived restoration study was performed to assess the effects of reconstruction on the community. It was focused on exploring the capacity of newly reconstructed neighborhoods to provide restorative experiences in case of disaster. The study was undertaken using the perceived restorativeness scale. The vulnerability variables that best explained the extent of the disaster were housing conditions, low household incomes and limited knowledge about tsunami events, which conditioned inadequate reactions to the emergency. These variables still constitute the same risks as a result of the reconstruction process, establishing that the occurrence of a similar event would result in a similar degree of devastation. For post-earthquake conditions, it was determined that all neighborhoods have the potential to be restorative environments soon after a tsunami. However, some neighborhoods are still located in areas devastated by the 2010 tsunami and again present high vulnerability to future tsunamis.
Understanding community-level flooding awareness in remote coastal towns in Northern Chile through community mapping
In 2015 and 2017 unusual ocean and atmospheric conditions produced many years’ worth of rainfall in short periods over Northern Chile’s Atacama Desert, resulting in catastrophic flooding in the town of Chañaral. However, the town is not only at risk of fluvial flooding, it is also at risk of tsunamis. Through a community mapping exercise, the authors attempted to establish the level of community awareness about tsunamis, and contrasted it with that of other types of water-related hazards facing the town (namely that of flooding due to high intensity rain). This was then compared with the results of field surveys and tsunami hazard simulations, indicating than overall the community appears to have better awareness than authorities about the threat posed by these types of events. The authors thus concluded that in cases when the community has a high level of hazard awareness (which in the case of Chile was the result of traditional knowledge being transmitted from previous generations) it would be advantageous to include them in discussions on how to improve disaster resilience.
The generation of new tsunami risk areas due to an intentionally biased reconstruction process: Case study of llico after the 2010 Chile tsunami
Tsunamis are among the most significant hazards in coastal settlements. Mitigation measures have been focused mainly on physical aspects, and few studies have addressed vulnerability and resilience in a multidimensional approach. The main objective of the present work is to assess changes in vulnerability and, consequently, risk, considering a time-space dimension. Three deterministic tsunami scenarios based on historical events were analyzed, and vulnerability analysis with an emphasis on social cohesion and community organization in prereconstruction (2012) and post-reconstruction (2017) conditions was carried out using physical, socioeconomic and social organization variables. The extreme scenario was found to be a 2010-like tsunami, and high levels of social trust and community cooperation were found in pre-reconstruction conditions, which decreased in post-reconstruction conditions due to the relocation of the affected population to other parts of the region. Therefore, it can be concluded that even though physical aspects are important for improving the livability of an affected place and the quality of life of its inhabitants, intentionally biased reconstruction processes (focused mainly on physical aspects) do not effectively reduce risk. Finally, it is crucial to include social capital and social resilience in public policies to implement more comprehensive and successful reconstruction processes.
Ex post analysis of engineered tsunami mitigation measures in the town of Dichato, Chile
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 against the costs of the mitigation measures. The obtained results show a reduction in the flooded area and a delay in the arrival times for the first smaller tsunami waves, but a negligible damage reduction when confronted to the largest waves. In conclusion, the tsunami mitigation measures would not have been effective to reduce the impact of the tsunami generated by the Maule earthquake in the town of Dichato, but could have had a benefit in retarding the inundation of low-land areas for the first smaller tsunami waves. The latter suggests that these works might be useful to mitigate storm waves or tsunamis of much smaller scales than the one that hit central-south Chile in 2010.