Role of debris flow on the change of 10Be concentration in rapidly eroding watersheds: a case study on the Seti River, central Nepal
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The concentration of cosmogenic 10Be in riverine sediments has been widely used as a proxy for catchment-wide denudation rate (CWDR). One of the key assumptions of this approach is that sediments originating from sub-basins with different erosional histories are well mixed. A tragic debris flow occurred in the Seti River watershed, central Nepal, on May 5, 2012. This catastrophic debris flow was triggered by slope failure on the peak of Annapurna IV and resulted in many casualties in the lower Seti Khola. However, it provided an opportunity to test the assumption of equal mixing of sediments in an understudied rapidly eroding watershed. This study documents the CWDR of 10Be to evaluate the extent of the influence of episodic erosional processes such as debris flow on the spatio-temporal redistribution of 10Be concentrations. Our data show that the debris flow caused little change in CWDR across the debris flow event. In addition to isotopic measurement, we calculated denudation rates by using the modeled concentrations in pre- and post-landslide sediments based on the local 10Be production rate. The modeled result showed little change across the event, indicating that the debris flow in May 2012 played a minor role in sediment evacuation, despite the rapid erosion in the catchment. Our study concludes that although the 2012 event caused many casualties and severe damage, it was a low-magnitude, high frequency event.
KeywordsSeti River Beryllium-10 (10Be) Catchment-wide denudation rate (CWDR) Debris flow Episodic erosional processes
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This research was supported by the College of Education, Korea University Grant in 2016. We would express sincere thanks to Ms. Su Young Lee, Prof. Kanhaiya Sapkota and Narendra Khanal for their help on initiation of this research and field survey. The early version of this manuscript was greatly improved thanks to the comments by Dr. J.M. Byun.
- Bhandary N, Dahal R., Okamura M (2012) Preliminary understanding of the Seti River debris-flood in Pokhara, Nepal, on May 5th, 2012-A report based on a quick field visit program. ISSMGE Bulletin 6 (4): 8–18Google Scholar
- Bollinger L, Avouac J, Beyssac O, et al. (2004) Thermal structure and exhumation history of the Lesser Himalaya in central Nepal. Tectonics 23: TC5015. DOI: 10.1029/2003TC001564Google Scholar
- Bookhagen B, Burbank DW (2006) Topography, relief, and TRMM-derived rainfall variations along the Himalaya. Geophysical Research Letters 33(8): L08405. DOI: 10.1029/2006GL026037Google Scholar
- Bookhagen B, Burbank DW (2010) Toward a complete Himalayan hydrological budget: Spatiotemporal distribution of snowmelt and rainfall and their impact on river discharge. Journal of Geophysical Research: Earth Surface 115(F3). DOI: 10.1029/2009JF001426Google Scholar
- Chmeleff J, von Blanckenburg F, Kossert K, et al. (2010) Determination of the 10Be half-life by multicollector ICP-MS and liquid scintillation counting. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 268 (2): 192–199. DOI: 10.1016/j.nimb.2009.09.012CrossRefGoogle Scholar
- Coe JA, Godt JW, Parise M, et al. (2003) Estimating debris-flow probability using fan stratigraphy, historic records, and drainage-basin morphology, Interstate 70 highway corridor, central Colorado, USA. In: Proc 3rd Int Conf on Debris Flow Hazard Mitigation. Mechanics, Prediction, and Assessment No. 2. Davos, Swiss. pp 1085-1096Google Scholar
- Gabet E, Langner H, Burbank DW, et al. (2004a) Geomorphic controls on chemical weathering rates in the High Himalayas of Nepal. In: Proceedings AGU Fall Meeting Abstracts.Google Scholar
- Herman F, Copeland P, Avouac JP, et al. (2010) Exhumation, crustal deformation, and thermal structure of the Nepal Himalaya derived from the inversion of thermochronological and thermobarometric data and modeling of the topography. Journal of Geophysical Research: Solid Earth 115(B6). DOI: 10.1029/2008JB006126Google Scholar
- Korschinek G, Bergmaier A, Faestermann T, et al. (2010) A new value for the half-life of 10Be by heavy-ion elastic recoil detection and liquid scintillation counting. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 268 (2): 187–191. DOI: 10.1016/j.nimb.2009.09.020CrossRefGoogle Scholar
- NASA (2012) Landslide and Deadly Flood in Nepal: Image of the Day. (Available online at: http://earthobservatory. nasa.gov/IOTD/view.php?id=78070&src=iotdrss, accessed on 24 May 2012)Google Scholar
- Petley D, Stark C (2012) Understanding the Seti River landslide in Nepal. (Available online at: http://blogs.agu.org/landslideblog/2012/05/23/understanding-the-seti-riverlandslide-in-nepal l, accessed on 2012-05-25).Google Scholar
- West AJ, Hetzel R, Li G, et al. (2014) Dilution of 10Be in detrital quartz by earthquake-induced landslides: Implications for determining denudation rates and potential to provide insights into landslide sediment dynamics. Earth and Planetary Science Letters 396: 143–153. DOI: 10.1016/j.epsl.2014.03.058CrossRefGoogle Scholar
- Wittmann H, von Blanckenburg F, Maurice L, et al. (2010) Sediment production and delivery in the Amazon River basin quantified by in situ-produced cosmogenic nuclides and recent river loads. Geological Society of America Bulletin B30317. DOI: 10.1130/B30317.1Google Scholar
- Yanites BJ, Tucker GE, Anderson RS (2009) Numerical and analytical models of cosmogenic radionuclide dynamics in landslide-dominated drainage basins. Journal of Geophysical Research: Earth Surface 114(F1). DOI: 10.1029/2008JF 00108Google Scholar