Slope instability in Nicaragua triggered by Hurricane Mitch: distribution of shallow mass movements

The heavy rains associated with Hurricane Mitch triggered off a number of slope instability processes in several Central American countries. Different instability processes have been acknowledged for the various mountainous regions of Nicaragua. An enormous movement of the Casita Volcano slopes resulted in numerous deaths and some deep movements have been reactivated. On the other hand, numerous shallow mass movements and debris flows have given rise to great material loss throughout a large part of Nicaraguan mountains.Mapping the shallow mass movements in an area of Central Nicaragua clearly reveals the close ties between their distribution and some geomorphological factors. A susceptibility model has been constructed for shallow mass movements based on field mapping of the shallow mass movement distribution, the geomorphological map as well as the digital slope and accumulated flow models. A logistical regression analysis was applied. The study area has been categorized into three classes of relative landslide susceptibility. Given that phenomena of this nature occur much more frequently in the high susceptibility class, 94% of the shallow mass movements that have been used to test the model are in the high and medium susceptibility classes . The geological and geomorphological conditions of the study area are representative of a large sector of the central Nicaraguan region. Consequently, the methodology followed in this paper is deemed to constitute a useful tool, both regarding the design of new infrastructures, and as a guide to the urban development of the area.