Landslides, hurricanes, and sediment sourcing impact basin-scale erosion estimates in Luquillo, Puerto Rico

Abstract Accurately inferring erosion rates from cosmogenic isotope concentrations in river sand assumes temporally steady concentrations; few studies test this assumption. Following Hurricane Maria in Puerto Rico, we quantified temporal variability in meteoric and in situ 10Be (10Bem, 10Bei) on sand-sized grains of riverine transported material in landslide-prone basins. We analyzed 20 samples collected over 18 months from the channels of two nested watersheds: the Icacos (3.14 km2, 0.09% active landslide area) and Guaba basins (0.11 km2, 1.23% active landslide area). 10Bei concentrations in Icacos basin sediment remained steady over time whereas concentrations in Guaba basin sediment were initially half those in the Icacos basin and increased linearly over 18 months, constraining recovery time to