Evolução morfodinâmica e riscos geológicos associados a zona costeira do Timor-Leste.

Abstract

The current and growing occupation of coastal environments, whether for the expansion and diversification of industrial areas, agriculture, or the growth of beach tourism, and its use without proper criteria, results in impacts and alterations that may lead to the degradation of the landscape and ecosystems, ultimately rendering the economic activities in these areas unfeasible. This, combined with the intense dynamics of the processes occurring in this environment—such as morphodynamics, sea level variations, erosion, and sediment transport—makes the coastal zone a highly complex area, with harmonious management being one of the greatest challenges of the 21st century. Considering the ability to utilize geological and oceanographic knowledge to diagnose environmental, topographical, eustatic, and geomorphological conditions, contributing to the identification of areas for human activities, preservation zones, and the mapping of geological hazard zones, this study aims to gain a deeper understanding of the main processes and conditions influencing the coastal morphodynamic evolution of Timor-Leste and identify the geological hazards present in this environment. For this purpose, an extensive literature review was conducted, utilizing doctoral theses, scientific articles, and books on topics ranging from regional geology and the formation of Timor Island, structural models, and tectonic evolution, to the concepts of morphodynamics and coastal evolution, geomorphological mapping and its various scales of work, geological hazards, and the region’s climate. Subsequently, a geomorphological mapping was carried out using GIS (Geographic Information Systems), employing QGIS 3.40 software at a 1:12,500 scale, covering the geomorphological units and subunits of the study area. Free satellite images were obtained from PlanetScope, with a spatial resolution of 3 meters per pixel, and free radar images from the ALOS PALSAR (Advanced Land Observing Satellite) remote sensor with a spatial resolution of 12.5 meters. The study area includes the coastal zones of the districts of Ainaro, Ambeno, Baucau, Bobonaro, Covalima, Díli (the capital), Lautém, Liquiçá, Manatuto, Manufahi, and Viqueque. Two main geomorphological units were identified: Coastal Plain and Mountains. A 10-day field survey was also conducted in April 2023 to collect sediment samples and describe sediment characteristics, as well as to verify the scale of work adopted in the geomorphological mapping. Finally, based on the studies and considering the morphodynamic aspects, the coastal region of Timor-Leste was divided into the northern and southern coasts, or, respectively, the Tectonic Coast¹ and Continental Shelf Reef Systems².