MARCA  logo usm

More news

Noticias

Categoría: Noticias

Tsunami Inundation detection model delivers data concerning evacuation times and propagation of waves in the Vergara Neighborhood.

By means of a quantitative analysis of the Vergara Neighborhood vulnerability, the initiative delivers data about the evacuation times and the propagation of waves in the event of a tsunami.

By means of a quantitative analysis of the Vergara Neighborhood vulnerability, the initiative delivers data about the evacuation times and the propagation of waves in the event of a tsunami.

 

file 20170821083244The main objective of the simulation model implemented by USM academics of the Departments of Architecture and Civil works is to analyze the vulnerability of the Great Valparaiso’s coastline in the event of a tsunami, specifically addressing the times of reaction, evacuation and the arrival of the first waves.

This research, -conducted within the collaborative framework between the think tank “Valparaiso Puerto Plus” and four V Region universities- pretends to be a contributor in terms of sectorial vulnerability, choosing Viña del Mar’s Vergara Neighborhood as the subject of the study, which geomorphological features makes it especially fragile against the impact of a flooding phenomenon triggered by a tsunami, vulnerability that has been recently incremented due to its high concentration of population and  amenities.

Among the geomorphological features that increase this area´s vulnerability, stands out the zone’s low elevation (less than 10 meters above sea level), the large extension of its coastal plain, which covers almost 2 km in certain spots and, lastly, the presence of the Marga- Marga estuary, a possible flooding entry point.

The study’s methodology took into account the implementation of a flooding computational model and an agent model. The first model evaluates aspects regarding the tsunami itself (arrival times, depth and area of flooding, flow speed, etc.), meanwhile, the second one consists in a modeling technique that codifies individual behavior during evacuation. Thus, the evacuation analysis of this proceeding allows calculating the required time to evacuate all the agents from a risk zone through the definition of a set of rules for their movement.

The agent evacuation model, additionally, was conducted in collaboration with the researcher Cyril Mokrani of the National Research Center for the Integrated Natural Disasters Management (CIGIDEN for its Spanish acronym). The team of professionals in charge of this model used the STOC-AGENT software, developed by Japan’s Port and Airport Research Institute (PARI). This allowed simulating pedestrian movement within the scenario studied (generated from seismic parameters similar to the 1730 earthquake) to then spatially superimpose this result with the expected propagation of a flooding caused by a tsunami.

Based on this, the professionals were able to calculate the required time to evacuate the zone and estimate the fatality rate corresponding to the people that would not be able to reach a secure zone before being overtaken by the propagating waters.

With this approach, the researchers concluded that the generated evacuation model illustrates that, in general, the Vergara Neighborhood inhabitants have good chances of evacuating in a reasonable amount of time after a high intensity, tsunami-generating earthquake (15 to 20 minutes). Nevertheless, there is a vulnerable area around the Casino that is topographically sunken and is farther away from the refuge or closest secure area. 

Additionally, it was shown that the time to reach the maximum water penetration is 45 minutes from the time of the tsunamigenic earthquake, which has direct influence on the percentage of the population reaching secure zones, the number of people moving towards refuge, and the percentage of fatalities (due to flooding). This last percentage could reach up to 5%, depending on the scenario of the catastrophe (night or morning peak time). 

These results have shown a great vulnerability of the area to the impact of near-field tsunamis. In the case of a seismic event of similar magnitude and location to the one registered in 1730, the tsunami could hit the researched coastline in only 18 minutes. Likewise, the low elevation of the Vergara Neighborhood (under 10 m.s.n.m.) would facilitate the propagation of inland flooding to up to 800 meters in some critical zones, as well as the water entry through the bed of the Marga-Marga estuary.

However, it is important to consider the last seismic experiences –for example, evacuation responses to the 2010 and 2015 earthquakes- where it has been called into question the real capacity of the population and emergency systems to respond rapidly and efficiently in the face of an event of such magnitude.

On this subject stand out traffic jams due to the use of cars to evacuate, low power and poorly situated sirens, which means the issued warnings are not heard by everyone, and the high influx of tourists in the area, who do not know the location of the evacuation routes and the corresponding secure zones.

Against this and, considering that structural solutions like the containment of an eventual flooding by means of dams and walls, are very complicated to execute in the short term, it is that this study calls to promote the evacuation as the most important response action against the threat of a tsunami. The last could be addressed through the creation a vertical evacuation spots system that would minimize the response time and the number of people moving, through systematic educational campaigns aimed at the population at large.

It is worth noting that the USM currently cooperates with the Hydrographic and Oceanographic Service of the Armada (SHOA for its Spanish acronym) in the elaboration and development of an Integrated Forecasting and Tsunami Warning system  (SIPAT for its Spanish acronym), that has been added to the National Tsunami Warning System, and whose main feature is the division of the country’s coastline in 21 different segments, with the objective of evacuating the population in the higher risk areas and not along the whole coast, as it was done in the past.  

 

Por ROBERTO BARRÍA, JORGE LEÓN Y PATRICIO CATALÁN
Académicos de los Departamentos de Arquitectura y Departamento de Obras Civiles
Universidad Técnica Federico Santa María

For further information: http://ingenium.usm.cl

Escrito por Super User 30 · Aug · 2017

[Volver]