High-resolution fluvial geomorphology of dynamic volcanic environments of Costa Rica, Central America

Costa Rica is a small humid tropical country with an extension of 51,179 km², it has an extensive network of diverse streams and rivers controlled by diverse environmental and geological conditions. Rugged terrain, active volcanism, and tectonic activity, along with intense and frequent precipitation, result in a dynamic drainage system characterized by a wide array of erosive and depositional fluvial landforms. Over 33% of Costa Rica’s territory is composed of Quaternary-Pleistocene volcanic landforms. These dynamic and high sediment source environments play a crucial role in the economy and society of the country. From the energy supply point of view, over 70% of the country’s electricity generation comes from hydropower plants located within volcanic formations. Mountain and highland volcanic areas are also the main source of drinking water for most of the population that live in the central part of Costa Rica.

Using remote sensing techniques (UAV photogrammetry and satellite imagery), bidimensional hydraulic modelling and raster analysis we analyzed with high-resolution (<1m/pixel) five fluvial-volcanic environments with different environmental conditions: (i) the effects of explosive phreatic eruptions on the channel morphology of the Pénjamo River located on the Rincón de la Vieja Volcano; (ii) severe bank erosion caused by an extreme precipitation event that damaged multiple structures along the Turrialba River, Turrialba Volcano; (iii) alluvial fan geomorphology of the Reventado River and it’s hazard implications to Cartago City, Irazú Volcano; (iv) confined urban streams and vegetation connectivity analysis of San José City, Irazú Volcano; (v) river dynamics and channel morphology  in extinct Pleistocene volcanic formations, San Lorencito River.

The use of the high-resolution assets allowed us to get novel insights on how channel morphology is composed in these extremely dynamic environments. Also, analyze how channels adjust to high sediment yield due to climatic or eruptive events. Some main outcomes of our research show that: (i) rivers in these steep environments flow confined mostly with single-thread morphologies and coarse sediments (boulders); (ii) volcanic phreatic eruptions generated hyperconcentrated flows (lahars) that caused severe bank erosion; (iii) vegetation in confined urban rivers play a key role in ecosystem management and environmental development; (iv) rivers that flow from active volcanoes transport extreme amounts of sediments and represent a major hazard for populated areas of Costa Rica.

Our results contribute to a better understanding of how river dynamics function under diverse volcanic environments of the country. Since over 40% of the country’s population lives within volcanic formations the data we provide contributes for a better environmental and risk assessment.