Hydrological Changes in the Runoff Pattern of La Estrella River, Costa Rica after the 1991 Limon Earthquake

In 1991, Costa Rica suffered an earthquake with a magnitude of 7.7 Mw on the Richter scale that lifted several sections of the Caribbean coastal platform. On average, the continental plate tilted by 0.7 metres, producing an immediate effect over the hydro-morphological conditions of numerous rivers in the region. The earthquake also triggered multiple landslides in the surrounding basins. Consequently, land use was heavily modified, resulting in higher local runoff coefficients. The increase in sediment load also modified the cross-sections in the deposition areas of the lowermost parts of the basins.

This study presents the impacts derived from such changes in the Estrella River, precisely at the epicentre of the earthquake. The Estrella River is an economically important area in the Caribbean coast of Costa Rica dedicated to production of banana. We present the analysis of unit hydrographs derived from a record of 40 years of events in La Estrella River and the changes observed in the runoff pattern derived from the earthquake of 1991.