Revista Geográfica de Chile Terra Australis

Analysis of land use change using remote sensing and GIS techniques in the Cazaderos forest, Loja province, Southern Ecuador

José Luis Muñoz Marcillo, Byron Cabrera Sinche, Theofilos Toulkeridis — Sat, 30 Dec 2023 00:00:00 -0300

The predominant aim of the current study has been to determine land use change over a period of eight years in the Cazaderos dry forest in the province of Loja in Ecuador using remote sensing and GIS techniques. The methodology employed included the application of supervised classification of multispectral satellite imag-es applied to freely available Landsat 8 images using Catalyst image processing software and the application of the Object Analysis technique, which is presented as the methodological protocol in remote sensing that offers the highest level of accuracy. This process was accompanied by complementary Geographical Infor-mation System (GIS) techniques that allowed spatialization and quantification of the resulting information. The Cazaderos dry forest in the period of analysis has suffered a significant spatial fragmentation dominated by the current presence of bare soils that were previously covered by dense shrubs and have undergone a process of deforestation. During the period 2013 - 2021 the deforestation process extended to an area of 1273.95 ha corresponding to 15.21% of the total surface of the study area while reforestation reached 1426.86 ha corresponding to 17.04% of the total surface.

Landscape modification induced by forest plantations in a section of the Maulino coastal forest, Chile

marco antonio pena, Alexandra Fuentes — Sat, 30 Dec 2023 00:00:00 -0300

In this work were quantified and assessed the recent changes in the landscape composition and configuration of the Maulino Coastal Forest, located in central Chile, strongly affected by the forest plantations expansion. To achieve that, a set of landscape metrics were applied on its main vegetation land covers; derived from the official vegetation and land use cadasters of 2009 and 2016. Within the relatively short study period addressed, it was possible to confirm important changes in the landscape of the study area, mainly driven by an increase in the area covered by forest in the form of relatively small, compact, and irregularly shaped patches, which influenced the constriction, disconnection, and distancing of those patches of native vegetation. These results widely agree with those referred by previous studies, thus confirming the permanence of the fragmenting process that have affected this type of forest and consequently, the urgency of implementing actions aimed to its management and conservation.

Settlement patterns in the rain flooding of the metropolitan nucleos of a city in northern Perú

Giancarlo Chapoñan Moyano, Percy Junior Castro Mejía, Erik Omar Escalona Aguilar — Sat, 30 Dec 2023 00:00:00 -0300

This research based its analysis on the construction of the risk of pluvial flooding in the study area with the purpose of establishing the relationship between settlement and urban waterproofing and how the occupation of the land and the location are involved in it. The results show that there is an inversely proportional relationship between Housing Density and the Soil Biotic Index, demonstrating that the formal settlement decreases its permeability at a speed 10 times greater than that of the informal settlement.

Fog water traps as a low-cost alternative source of water in coastal desert areas of the Pacific

Sat, 30 Dec 2023 00:00:00 -0300

Water scarcity is the most common concept associated with the desert. The Atacama Desert is worldly known as the aridest desert on Earth. However, some populations are established in this area, requiring water for living that promotes the search of alternative water sources, as fog catchers taking in advance the regional fog event known as Camanchaca. During 2015, the construction of fog trap units was carried out on a hill in the Falda Verde sector in Chañaral (North Chile). In the design of these new fog trap units it was considered to improve the anchoring system and the distribution and angles of the clamping tensioners in order that the structure could withstand the maximum wind speeds that have been registered in the area, while recording the water accumulated by these units during a period of 12 months determined an average catchment of 22 liters of water/m² per month.

Evaluation of vulnerability to Tsunamis in the city of Puntarenas, Costa Rica

Diego Mesén, Gustavo Barrantes Castillo — Sat, 30 Dec 2023 00:00:00 -0300

An estimate of vulnerability to tsunamis was made in the city of Puntarenas, Costa Rica, using the Minimum Geostatistical Units (UGM) contained in the 2011 Population and Housing Census for the country. Vulnerability was defined based on four subvariables: disabled and dependent population, poverty, education and exposure, which in turn were grouped into two variables: socioeconomic and environmental, to finally have a total of 13 explanatory indicators. Once the vulnerability scheme was defined, the census information was collected and the calculations were made. The results obtained were four maps for each subvariable and an integrated map of the vulnerability index.

Use of unmanned aerial vehicle (UAV) in the analysis of natural risks: Landslides in the Ancoa Reservoir Sector, Linares Province, Maule Region.

Sat, 30 Dec 2023 00:00:00 -0300

On July 20, 2022 at 9:00 p.m., a landslide-type mass removal was recorded on route L-39, specifically at km 30.7 of the area of the first viewpoint of the Ancoa Reservoir, which is frequented by residents and visitors who come to this tourist sector. The landslide generated a road cut of 200 m, with the affected area of the hillside approximately 5,251 m². UAV (Unmanned Aerial Vehicle) flight was carried out in the study area, to obtain geographic information, data collection and geomorphological surface processes of the landslide, based on orthophoto measurements and generation of surface elevation models (DSM). The results show that photogrammetry from UAVs provides flexible and effective tools to evaluate and analyze geomorphological characteristics, in addition to mapping and monitoring this type of mass removal, being the basis for generating multitemporal studies.

Hydrological modeling for the discharge production in an experimental area of the Guayas river basin, Ecuador

José Luis Muñoz Marcillo, Theofilos Toulkeridis — Sat, 30 Dec 2023 00:00:00 -0300

Hydrological simulation is a vital issue within the comprehensive management of hydrographic basins, with estimates being an input for decision-making by territorial managers. The objective of the current study is to conduct the hydrological modeling of an experimental basin of the Guayas River, where the discharge of the Baba River will be simulated using the HEC-HMS hydrological modeler. Hereby, the morphometric and hydrological modeling of the basin was performed from a global DEM (ASTER GDEM) in an environment of Geographic Information Systems (GIS) complemented with the analysis of thematic coverage of land types and uses as well as of precipitation data for the sector. The simulation of the discharge of the experimental basin determined that twenty percent of the precipitation that fell in the time window of analysis generated direct runoff and the residual eighty percent is attributed to abstractions. This is a condition that is given by the presence of agricultural crops corresponding to seventy percent forest masses, native forest and shrubby vegetation, as well as by the interception processes as well as water catchment systems in the urban area. The adequate results obtained in the application of the HEC - HMS model are based on the previous work of physical and hydrological characterization of the basin expressed through the physiographic structure of the basin and the valorization of the parameters that characterize the hydrological processes. This research tends to be useful for small hydrographic basins in Ecuador that play an important role in the ecosystem and lack of hydrometeorological information.

Hydrogeological investigation of the Paine Aquifer considering baseline conditions from 1970 and long - term analysis from 1990 to 2020

Sat, 30 Dec 2023 00:00:00 -0300

Groundwater resources are vital for meeting the world's freshwater needs, providing the primary source of drinking water for nearly half the global population, and are particularly important for agriculture and industry in dry regions. The Paine Basin, situated south of Santiago, Chile, has been heavily affected by an extended mega-drought, influencing water availability for various uses. Yet, comprehensive hydrogeological studies to understand the aquifer system and establish a baseline for future actions in the basin to better manage water resources have been lacking. Therefore, this study investigates the aquifer's conditions in 1970, considered closest to its undisturbed state. It uses water table and chemical data to discern groundwater flow directions and the relationship between the river and the aquifer. Subsequent temporal analyses using Mann-Kendall tests and Theil-Sen slope estimation on DGA well-level data aim to statistically verify the significance of water level declines. The findings confirm an east-to-west groundwater flow, corroborated by chemical signatures linking the Paine waters to the Maipo River, suggesting river recharge from the aquifer during that era. However, recent trends indicate a significant drop in water levels since the mega-drought began in 2010, not aligning with the increase in groundwater extractions starting in 2005. The above highlights that additional water sources, such as river infiltration or irrigation return flow, need to be considered to explain water level variability, which highlights the hydrology of the basin. Finally, trend analysis over the last 30 years indicates that hydrodynamic conditions have changed since the initial conditions were considered in 1970.

Analysis of the geographic coverage of public hospital beds in Chile

Manuel FUENZALIDA, Fernando Crespo, Italo Lanio — Sat, 30 Dec 2023 00:00:00 -0300

Currently it is possible to observe various problems in our country associated with access to the hospital system, which could be largely due to the location or territorial location of the population, by virtue of this, there is an interest in knowing if public hospital care depends to a great extent on where one lives in Chile. A cross-sectional study is carried out using the Hospital Discharge Statistical Report (years 2015 to 2019), selecting the 177 public hospitals that provide care for more than one of the following pathologies: Tumors, Diseases of the circulatory system, respiratory system, digestive and genitourinary system. Total hospital discharges were classified into three levels of geographic coverage based on the patient's place of residence: local, adjacent, and non-adjacent. The analysis database comprised of Discharges, Beds, ICU Beds, ICU Beds, Coverage 1, Coverage 2, and Coverage 3 was grouped using the K-Means method. It was possible to identify 5 classes that explain different levels of variability in the geographical coverage of a hospital, these being called: very low, medium low, medium, high and very high. The methodology used in this study, it was possible to obtain the result that there are patients better located in the territory and that, therefore, they have more expeditious access to take advantage of the supply of hospital beds based on their needs or preferences.

Editorial

Carlos Prado Casanova — Sat, 30 Dec 2023 00:00:00 -0300