Descripción: According to the global predictions by the International Panel of Climate Change (IPCC), the sea-level rise due to ocean thermal expansion and glacier mass loss will average 0.09 - 0.88 m between 1990 and 2100, with a trend toward an increasing rise rate. Potential impacts of this increasing rise rate relate to changes in the coastal area, including floods, increased coastal retreat, and saline intrusion in the coastal acquiferous and estuaries. In order to achieve an appropriate coastal management scheme in the Province of Río Negro, the area was divided into zones to show information of the level of hazard on a simple map. To identify areas of geological hazard related to permanent and/ or episodic floods, a database was prepared. The threatened or in-danger areas were identified by means of coastal vulnerability indices, also called susceptibility indices, which were calculated by means of an algorithm that relates different variables obtained from coastal geology, and oceanographic and climatological information. This index is defined by seven variables and can be used to identify areas in risk of erosion or permanent/temporary flood. The most vulnerable areas to sea level rise are Balneario El Salado (Playas Doradas), San Antonio Oeste - San Antonio Este, Caleta de los Loros, and the Río Negro mouth. By contrast, vulnerability of the coastal area located to the south of Punta Pórfido is low. © 2004 Asociación Geológica Argentina.

Descripción: In the region of the Main Andes of San Juan, exists a high concentration of landslide deposits that can originate natural dams. The outburst of these dams generated by slide is a common process in this morphology. The analyses of satellite imagery and air photos of previous years allow reconstructing the characteristics and the origin of the slides that formed those natural dams. In this region of the Main Andes, the rapid uplift and erosion of the mountain chain has created abrupt slopes and an internal structure in the materials that determined an increase of the susceptibility to the slope collapse without triggers as the seismic activity or precipitations. The objectives of the present work are (1) to analyze the causes that formed the natural dam and produced the landslide dam and development of the Los Erizos lagoon in the middle course of the Santa Cruz river; (2) the outburst of the dam and their consequent flood; and (3) the morphologic characteristic of the study region. The temporary comparison between air photos with satellite imageries indicates that the natural dam was generated by slip of the western hillside of the Santa Cruz mountain range, located below the Cerro Estrella. However, the constant water flow to the lagoon, has increased its water level until reaching the maximum benchmark of the dam, produced the beginning of the lake drainage and weakening of the dam causing the outburst and its consequent flood. Based on satellite imagery, a temporary analysis of the lagoon is presented, indicating that monitoring is an important tool to alert in the whole San Juan river basin for possible natural dikes, preventing hazards to the populations down water. The alluvium of November 12 of 2005, discharged 32.100.000 m3 in 67 minutes and traveled 254 km in less than 12 hours.