Costa Rica features three major drainage basins, encompassing 34 watersheds with numerous rivers and tributaries, one large lake for hydroelectric generation, and two major aquifers that store 90% of the municipal, industrial and agricultural water. Additionally, volcanic activity has formed highly permeable subterranean layers within the fragmented igneous lava. This phenomenon coupled with high rainfall has created the formation of aquifers in the central and northern part of Costa Rica’s Central Valley, where more than half of the population lives. These aquifers are called the Upper and Lower Colima and are separated by a layer that acts as a semi-permeable aquitard, which allows the descending and ascending vertical transfer of water, a valuable asset considering annual precipitation in Costa Rica can range anywhere from four to eighteen feet annually. Source
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| A map illustrating the vast and entangled river systems throughout Costa Rica. |
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| A water flow grid of Costa Rica, illustrating the direction of flow throughout the country as a result of its complex geographic terrain. |
Unfortunately, the Atlantic Ocean side of Costa Rica is challenged with storm water drainage problems where water tables are not very deep, and the propensity for flooding is higher. Coupled with heavy rainfall (often an effect of high wind hurricanes), and sizeable earthquake activity, Costa Rica’s landscape is often burdened with landslides. Landslide effects on alluvial fans include direct deposition of material on fan surfaces alone the coast; fissuring and displacement of fan materials; alterations to drainage basins such as devegetation, denudation, and changes in channel networks; and generation of large amounts of sediment that may be transported to fans by post-earthquake water flows and debris flows. Source
These photos illustrate the incredible damage that can result from the extreme impact a landslide in Costa Rica can have on the landscape.
Landslide from Costa Rica Earthquake 9-5-2012
A landslide from mass rainfall in Costa Rica 12-29-11
Below is a photo of a steep cliff face wall, a zone of active slope
failure, from the dome at Costa Rica’s Poás Volcano after a small eruption in January
2008. At the root of the cliff lies a terrace of debris from mass wasting falls.
Here, an Earth Scientist examines Early Holocene fluvial sediments, in Esterillos, Costa Rica, from deposits on the Atlantic side of the
country, exhibiting great amounts of weathering due to the humid and tropical
climate.
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