TY - JOUR A1 - Tolorza, Violeta A1 - Mohr, Christian Heinrich A1 - Carretier, Sebastien A1 - Serey, Amador A1 - Sepulveda, Sergio A. A1 - Tapia, Joseline A1 - Pinto, Luisa T1 - Suspended sediments in chilean rivers reveal low postseismic erosion after the maule earthquake (Mw 8.8) during a severe drought JF - Journal of geophysical research : Earth surface N2 - We address the question of whether all large-magnitude earthquakes produce an erosion peak in the subaerial components of fluvial catchments. We evaluate the sediment flux response to the Maule earthquake in the Chilean Andes (Mw 8.8) using daily suspended sediment records from 31 river gauges. The catchments cover drainage areas of 350 to around 10,000 km(2), including a wide range of topographic slopes and vegetation cover of the Andean western flank. We compare the 3- to 8-year postseismic record of sediment flux to each of the following preseismic periods: (1) all preseismic data, (2) a 3-year period prior to the seismic event, and (3) the driest preseismic periods, as drought conditions prevailed in the postseismic period. Following the earthquake, no increases in suspended sediment flux were observed for moderate to high percentiles of the streamflow distribution (mean, median, and >= 75th percentile). However, more than half of the examined stations showed increased sediment flux during baseflow. By using a Random Forest approach, we evaluate the contributions of seismic intensities, peak ground accelerations, co-seismic landslides, hydroclimatic conditions, topography, lithology, and land cover to explain the observed changes in suspended sediment concentration and fluxes. We find that the best predictors are hillslope gradient, low-vegetation cover, and changes in streamflow discharge. This finding suggests a combined first-order control of topography, land cover, and hydrology on the catchment-wide erosion response. We infer a reduced sediment connectivity due to the postseismic drought, which increased the residence time of sediment detached and remobilized following the Maule earthquake. KW - earthquake KW - suspended sediment KW - Maule megathrust KW - Chile KW - catchment Y1 - 2019 U6 - https://doi.org/10.1029/2018JF004766 SN - 2169-9003 SN - 2169-9011 VL - 124 IS - 6 SP - 1378 EP - 1397 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Mohr, Christian Heinrich A1 - Coppus, Ruben A1 - Iroume, Andres A1 - Huber, Anton A1 - Bronstert, Axel T1 - Runoff generation and soil erosion processes after clear cutting JF - Journal of geophysical research : Earth surface N2 - Timber harvesting by clear cutting is known to impose environmental impacts, including severe disturbance of the soil hydraulic properties which intensify the frequency and magnitude of surface runoff and soil erosion. However, it remains unanswered if harvest areas act as sources or sinks for runoff and soil erosion and whether such behavior operates in a steady state or evolves through time. For this purpose, 92 small-scale rainfall simulations of different intensities were carried out under pine plantation conditions and on two clear-cut harvest areas of different age. Nonparametrical Random Forest statistical models were set up to quantify the impact of environmental variables on the hydrological and erosion response. Regardless of the applied rainfall intensity, runoff always initiated first and yielded most under plantation cover. Counter to expectations, infiltration rates increased after logging activities. Once a threshold rainfall intensity of 20mm/h was exceeded, the younger harvest area started to act as a source for both runoff and erosion after connectivity was established, whereas it remained a sink under lower applied rainfall intensities. The results suggest that the impact of microtopography on surface runoff connectivity and water-repellent properties of the topsoil act as first-order controls for the hydrological and erosion processes in such environments. Fast rainfall-runoff response, sediment-discharge-hystereses, and enhanced postlogging groundwater recharge at catchment scale support our interpretation. At the end, we show the need to account for nonstationary hydrological and erosional behavior of harvest areas, a fact previously unappreciated in predictive models. KW - infiltration KW - runoff KW - erosion KW - connectivity KW - rainfall simulation KW - catchment Y1 - 2013 U6 - https://doi.org/10.1002/jgrf.20047 SN - 2169-9003 VL - 118 IS - 2 SP - 814 EP - 831 PB - American Geophysical Union CY - Washington ER -