Channel morphology in an active volcanic complex under humid tropical conditions

Active volcanic landscapes are among the most energetic sedimentary systems on Earth. Rivers that flow through these terrains are extremely dynamic and experience rapid changes in their channel morphology. Channel morphology classification in humid tropical contexts near to active volcanoes has received little attention within geomorphological science. We applied diverse remote sensing techniques and carried out field observations to characterize with high-spatial resolution the channel morphology of four rivers that drain from the Irazú-Turrialba Volcanic Complex located in Costa Rica. This particular environment has extreme precipitation events, frequent high-magnitude earthquakes, dense vegetation, and active volcanic activity. We found that this highly energetic landscape contains unusual single-thread and multithread channels with steep-slopes, high-confinement, and coarse sediments, mainly composed of boulders. We therefore review the applicability of existing channel morphology classification schemes to this particular environment. Our findings provide novel insights into fluvial geomorphology around active volcanoes with tropical humid climates. • Fluvial geomorphology in this highly energetic volcanic complex is dominated by colluvial and pseudo meandering channels which are steep, confined, and transport limited. • Existing channel morphology classification schemes partially fail when applied to this particular environment. • Main sediment sources are located in key landforms such as craters and caldera collapses.