Based on the analysis of the latest multispectral satellite images provided by the United States Space Agency (NASA) and the European Space Agency (ESA), a group of academics and researchers from the Geo-information and Remote Sensing Laboratory of the Institute of Geography of The Pontifical Catholic University of Valparaíso prepared a map of the fire and affected areas to understand how the incident behaved, its progress and geographical conditions.
The report indicates that it was inevitable that the fire, which began as a forest fire, would end up affecting the surrounding urban settlements, also that the weather conditions were conducive to triggering a mega fire, that the topographic irregularity of the area turned the fire into an eruptive one and that the Lake Peñuelas acted as a natural firebreak to stop the advance from its origin near Route 68 towards Valparaíso.
The work was developed by the director of the Geo-information and Remote Perception Laboratory of the PUCV, Roberto Chávez, together with the researchers Matías Pérez, Sebastián Fuentes and Gabriel Castro. The academic of the PUCV Institute of Geography Luis Álvarez and the professor of the University of Chile, Miguel Castillo, who is part of the Forest Fire Engineering Laboratory of the study house, also participated in the preparation. The scientists carried out the evaluation of the burned area and severity of the fire using a satellite analysis technique that yields precise indices by comparing an image before the fire and one after the fire.
The first satellite image was taken by the ESA Sentinel 3 satellite on February 3, 2024 at 11:33 local time, which is completely free of clouds, allowing you to observe the multiple active hotspots and smoke plumes. projecting towards the north. The image corresponds, in scientific terms, to a visualization called “fire scar” or “fire scar” using the combination of SWIR, NIR and Red spectral bands of the multispectral image, which, explained Roberto Chavez, “are multispectral captures of certain information or images beyond the visible spectrum, which is what our eyes would capture if we were on top of an airplane. These images have visible bands (red, green and blue), but they also have other parts of the electromagnetic spectrum that our eyes cannot perceive.”
On the other hand, the cloud-free image was available prior to the fire, on December 20, 2023, while the capture after the fire corresponds to February 5, 2024, a date on which the emergency, leaving some minor advance vectors active. Those records were captured by Landsat satellites, which take images every 16 days.
The scientists calculated the normalized burnt area index (NBR) for the images before and after the fire, and then, by subtraction or difference between the two (dNBR), estimate the severity of the fire in terms of burned vegetation cover. According to this mathematics, the affected area reaches 9,429 hectares, which considers areas of low, medium and high severity.
“The severity estimates depend on the biophysical criteria of the area, this means that they are patterns, there are elements that appear and disappear in the territory and that are captured by the spectral bands of the satellite, this is the fuel that is found at the territorial which is basically vegetation, dry grass, bushes, trees, forest plantations and wood, which is also in the houses that were affected later,” Chávez pointed out.
Report
Through the calculation, the first events of the catastrophe were observed. “In the sector where the fire started (La Engorda sector in Las Tablas), the severity is low-medium, but to the extent that the fire was projected towards abyssal structures (ravines and ravines), the level of severity increased. In this first section of advance, the main vegetation affected by the fire corresponded to adult mosaics of Eucalyptus globulus and semi-dense shrublands interspersed with other tree species, including aromatic pine and remnants of distinguished pine. All of these formations have high ignition power and flammability, further accentuated by the low humidity of the fine fuel on the floor of the leaf litter, grasslands and organic mantle,” the report says.
In this abrupt topography, the fire gains size and advances towards populated areas. “On this route, and after passing the Lago Peñuelas Reserve in its advance towards the north, the fire encounters a chain of hills dominated by adult palm groves and mixtures of scrub in the high parts and remnants of forests at the bottom of ravines. In fact, by observing the red stripes (of greater severity) projected to the axis of the Viña del Mar estuary, it was possible to identify the streams of El Quiteño, El Salto, and Marga Marga, where the fire acquired extreme behavior due to the supply of oxygen as a result of the inclination of the flames on a slope, and direction downwind which, in the initial development of the emergency, had a propagation vector from the Southwest to the North-Northeast. Something similar occurred in the ravines on the southern slopes of the Estero de Viña del Mar basin and also in the focus in the El Rincón sector of Villa Alemana,” indicates the work carried out at the PUCV.
The group of scientists reached a series of worrying conclusions for the Valparaíso Region, among them, the assertion of academic Luis Álvarez, who explains in the report that “every megafire that starts out as a forest fire ends up as structural because any focus of the peripheral arc of the Greater Valparaíso is inevitably projected into the city”, so the professor also assures that “the suburban peripheries and the conditions of rurality, with respect to their uses in the surrounding arc to the south of the area, is a vulnerability that must be addressed from end to end because Fire is incubated and projected there as a risk due to the deterioration and abandonment of plantations, especially highly combustible eucalyptus trees. The owners are absent due to lack of opportunity because the land is superfluous, a place that is not cared for burns due to negligence, accidents or pyromania. In this case, the main focus began in Las Tablas or Camino Viejo to Santiago, which is in a state of abandonment, it is a place of clandestine dumping and garbage.”
Finally, the researcher stressed that the purpose of the report is to explain from the objectivity of science the variables that can cause fires, “the projection of the fire and the eruptive condition respond to the development of the report, there are explanations for the inhabitants who must adhere to the knowledge, a more educated city is also a safer city.
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