Evaluation of exposure to mass movement processes using UAV-acquired aerial imagery: insights after the 2021 El Chiquihuite hill disaster, Estado de Mexico, Mexico
Authors: Garnica-Peña Ricardo , Alcántara-Ayala Irasema 
Published: June 2022

&lt;p&gt;Due to geological, geomorphological, hydrometeorological and anthropic factors, the occurrence of mass movement processes is recurrent in the Metropolitan Area of the Valley of Mexico (MAVM). Historically, earthquake and precipitation events have triggered landslides in the mountainous areas of the MAVM.&lt;/p&gt;&lt;p&gt;These events occur in densely populated areas on which disaster risk has been constructed. Given that families have settled for decades in areas highly susceptible to landslides, disaster risk is the expression of the growing exposure of vulnerable groups of people to this and other types of hazards. A recent example of this problem is found in the north of the city, on the so-called El Chiquihuite hill, located in the mountainous area of &amp;#8203;&amp;#8203;the Sierra de Guadalupe, which forms the northern limit of the city.&lt;/p&gt;&lt;p&gt;The Sierra de Guadalupe is made up of volcanic structures, such as collapsed domes and stratovolcanoes, which have associated fall deposits, pyroclastic flows, and mudflows. Among these domes is the Cerro El Chiquihuite in which the occurrence of rock falls is constant and represents a serious hazard to the inhabitants located at the base of the slopes of this volcanic complex. This was made clear on September 10, 2021, when 200 tons of rocks fell, burying a dozen homes which involved four fatal victims.&lt;/p&gt;&lt;p&gt;The Sierra de Guadalupe is composed by volcanic structures, such as collapsed domes and stratovolcanoes, that have associated fallout deposits, pyroclastic flows, and mudflows. Among these domes is El Chiquihuite hill, in which the occurrence of rockfalls is constant and represents a serious hazard for the inhabitants living at the base of the slopes of this volcanic complex. This became clear on September 10, 2021, when 200 tons of rocks fell, burying a dozen homes and causing four fatalities.&lt;/p&gt;&lt;p&gt;In the affected area, evaluations have been carried out focused mainly on the study of the hazard associated with the fall of rock masses, but little has been done to evaluate the exposure and vulnerability conditions of the population that inhabits the area. In this work we analyse through very high-resolution aerial images, the level of exposure of the houses that are located on the slopes of El Chiquihuite hill. This work consisted in the acquisition of photographs using an Unmanned Aerial Vehicle and the corresponding processing to obtain detailed cartography and three-dimensional models that served as tools to evaluate the exposure conditions, as well as to extract some characteristics of the houses.&lt;/p&gt;&lt;p&gt;The results of this work can be used by Civil Protection authorities to design both prevention and response plans through the use of large-scale mapping. In addition, this type of method can be replicated to monitor the processes of urban expansion on the slopes of El Chiquihuite hill to monitor, manage and reduce the exposure of families to the continuous occurrence of mass movement processes.&lt;/p&gt;