Avance en la prevención de desastres naturales en la cuenca del río Paute, Ecuador

Abstract

Advances in the prevention of natural disasters in the rio Paute drainage, Ecuador The enormous Josefina landslide that dammed the Paute river in March 1993 and its terrible consequences have clearly shown the importance of recognising natural disaster phenomena and the lack or prevention studies. Based on this experience, the Swiss Disaster Relief Unit together with Ecuadorian institutions began a multidisciplinary pilot project in 1994 to run until 1997 to study and monitor the different natural phenomena that could affect the Paute river basin whose area is 3.700 km2. Here are located Cuenca, the third city of the country, and the rural regions for a total of 700.000 inhabitants. Some results of the first year of studies are herein presented for 2 of the 6 fields of research. The geological studies have identified the unstable terrains and mapped the geology, the phenomena and the hazards at 1:25.000 scale covering 380 km2. The unstable zones were classified as active, latent or relict which embrace volumes between 1 x 105 and 1 x 109 m3 . These instabilities are chiefly related to incompetent sedimentary and metamorphic rocks and coluvial deposits or eluvions. The phenomena are aggravated in the rainy seasons. Sixteen zones of major active landslides were identified, which were studied on a scale of 1:10.000 with speed vector maps. A special case is the Paccha landslide that attained movements up to 8.400 cm /year. A geodesic monitoring network has been installed to investigate more precisely these zones. In the area of hydrometeorology an automatic network is being implemented to monitor and give flood alerts. Also flood studies in the four rivers of the city of Cuenca (Pop. 400.000) shows its high vulnerability based upon flood propagation models for 10 yrs. and 1000 yrs. The regions of risk were identified in probable inundation maps, complemented with recommendations and conclusions. In addition the project strengthens the seismological network in Southern Ecuador and the limnological monitoring of the Josefina Lakes. Finally we are collaborating to improve Civil Defence and to transfer new technology with outside professional help and teaching. The interinstitutional collaboration and the continuos diffusion of the results have already promoted regional planning and infrastructure development.