TY - JOUR A1 - Stolle, Amelie A1 - Schwanghart, Wolfgang A1 - Andermann, Christoff A1 - Bernhardt, Anne A1 - Fort, Monique A1 - Jansen, John D. A1 - Wittmann, Hella A1 - Merchel, Silke A1 - Rugel, Georg A1 - Adhikari, Basanta Raj A1 - Korup, Oliver T1 - Protracted river response to medieval earthquakes JF - Earth surface processes and landforms : the journal of the British Geomorphological Research Group N2 - Mountain rivers respond to strong earthquakes by rapidly aggrading to accommodate excess sediment delivered by co-seismic landslides. Detailed sediment budgets indicate that rivers need several years to decades to recover from seismic disturbances, depending on how recovery is defined. We examine three principal proxies of river recovery after earthquake-induced sediment pulses around Pokhara, Nepal's second largest city. Freshly exhumed cohorts of floodplain trees in growth position indicate rapid and pulsed sedimentation that formed a fan covering 150 km2 in a Lesser Himalayan basin with tens of metres of debris between the 11th and 15th centuries AD. Radiocarbon dates of buried trees are consistent with those of nearby valley deposits linked to major medieval earthquakes, such that we can estimate average rates of re-incision since. We combine high-resolution digital elevation data, geodetic field surveys, aerial photos, and dated tree trunks to reconstruct geomorphic marker surfaces. The volumes of sediment relative to these surfaces require average net sediment yields of up to 4200 t km–2 yr–1 for the 650 years since the last inferred earthquake-triggered sediment pulse. The lithological composition of channel bedload differs from that of local bedrock, confirming that rivers are still mostly evacuating medieval valley fills, locally incising at rates of up to 0.2 m yr–1. Pronounced knickpoints and epigenetic gorges at tributary junctions further illustrate the protracted fluvial response; only the distal portions of the earthquake-derived sediment wedges have been cut to near their base. Our results challenge the notion that mountain rivers recover speedily from earthquakes within years to decades. The valley fills around Pokhara show that even highly erosive Himalayan rivers may need more than several centuries to adjust to catastrophic perturbations. Our results motivate some rethinking of post-seismic hazard appraisals and infrastructural planning in active mountain regions. KW - fluvial response KW - sediment yield KW - earthquakes KW - Nepal KW - Himalaya Y1 - 2018 U6 - https://doi.org/10.1002/esp.4517 SN - 0197-9337 SN - 1096-9837 VL - 44 IS - 1 SP - 331 EP - 341 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Schwanghart, Wolfgang A1 - Bernhardt, Anne A1 - Stolle, Amelie A1 - Hoelzmann, Philipp A1 - Adhikari, Basanta R. A1 - Andermann, Christoff A1 - Tofelde, Stefanie A1 - Merchel, Silke A1 - Rugel, Georg A1 - Fort, Monique A1 - Korup, Oliver T1 - Repeated catastrophic valley infill following medieval earthquakes in the Nepal Himalaya JF - Science N2 - Geomorphic footprints of past large Himalayan earthquakes are elusive, although they are urgently needed for gauging and predicting recovery times of seismically perturbed mountain landscapes. We present evidence of catastrophic valley infill following at least three medieval earthquakes in the Nepal Himalaya. Radiocarbon dates from peat beds, plant macrofossils, and humic silts in fine-grained tributary sediments near Pokhara, Nepal’s second-largest city, match the timing of nearby M > 8 earthquakes in ~1100, 1255, and 1344 C.E. The upstream dip of tributary valley fills and x-ray fluorescence spectrometry of their provenance rule out local sources. Instead, geomorphic and sedimentary evidence is consistent with catastrophic fluvial aggradation and debris flows that had plugged several tributaries with tens of meters of calcareous sediment from a Higher Himalayan source >60 kilometers away. Y1 - 2016 U6 - https://doi.org/10.1126/science.aac9865 SN - 0036-8075 SN - 1095-9203 VL - 351 SP - 147 EP - 150 PB - American Assoc. for the Advancement of Science CY - Washington ER - TY - JOUR A1 - Stolle, Amelie A1 - Bernhardt, Anne A1 - Schwanghart, Wolfgang A1 - Hoelzmann, Philipp A1 - Adhikari, Basanta R. A1 - Fort, Monique A1 - Korup, Oliver T1 - Catastrophic valley fills record large Himalayan earthquakes, Pokhara, Nepal JF - Quaternary science reviews : the international multidisciplinary research and review journal KW - Catastrophic valley infill KW - Great Himalayan earthquakes KW - Radiocarbon age dating KW - Provenance analysis KW - Paleoseismology KW - Nepal Y1 - 2017 U6 - https://doi.org/10.1016/j.quascirev.2017.10.015 SN - 0277-3791 VL - 177 SP - 88 EP - 103 PB - Elsevier CY - Oxford ER -