@article{RamachandranRupakhetiLawrence2020,
  author    = {Ramachandran, Srikanthan and Rupakheti, Maheswar and Lawrence, Mark},
  title     = {Black carbon dominates the aerosol absorption over the Indo-Gangetic Plain and the Himalayan foothills},
  series = {Environment international : a journal of science, technology, health, monitoring and policy},
  volume    = {142},
  journal   = {Environment international : a journal of science, technology, health, monitoring and policy},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0160-4120},
  doi       = {10.1016/j.envint.2020.105814},
  pages     = {12},
  year      = {2020},
  abstract  = {This study, based on new and high quality in situ observations, quantifies for the first time, the individual contributions of light-absorbing aerosols (black carbon (BC), brown carbon (BrC) and dust) to aerosol absorption over the Indo-Gangetic Plain (IGP) and the Himalayan foothill region, a relatively poorly studied region with several sensitive ecosystems of global importance, as well as highly vulnerable populations. The annual and seasonal average single scattering albedo (SSA) over Kathmandu is the lowest of all the locations. The SSA over Kathmandu is < 0.89 during all seasons, which confirms the dominance of light-absorbing carbonaceous aerosols from local and regional sources over Kathmandu. It is observed here that the SSA decreases with increasing elevation, confirming the dominance of light absorbing carbonaceous aerosols at higher elevations. In contrast, the SSA over the IGP does not exhibit a pronounced spatial variation. BC dominates (>= 75\%) the aerosol absorption over the IGP and the Himalayan foothills throughout the year. Higher BC concentration at elevated locations in the Himalayas leads to lower SSA at elevated locations in the Himalayas. The contribution of dust to aerosol absorption is higher throughout the year over the IGP than over the Himalayan foothills. The aerosol absorption over South Asia is very high, exceeding available observations over East Asia, and also exceeds previous model estimates. This quantification will be valuable as observational constraints to help improve regional simulations of climate change, impacts on the glaciers and the hydrological cycle, and will help to direct the focus towards BC as the main contributor to aerosol-induced warming in the region.},
  language  = {en}
}
@phdthesis{Fischer2022,
  author    = {Fischer, Melanie},
  title     = {Outburst floods in the Greater Himalayas},
  doi       = {10.25932/publishup-56997},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-569972},
  school      = {Universit{\"a}t Potsdam},
  pages     = {xviii, 155},
  year      = {2022},
  abstract  = {High-mountain regions provide valuable ecosystem services, including food, water, and energy production, to more than 900 million people worldwide. Projections hold, that this population number will rapidly increase in the next decades, accompanied by a continued urbanisation of cities located in mountain valleys. One of the manifestations of this ongoing socio-economic change of mountain societies is a rise in settlement areas and transportation infrastructure while an increased power need fuels the construction of hydropower plants along rivers in the high-mountain regions of the world. However, physical processes governing the cryosphere of these regions are highly sensitive to changes in climate and a global warming will likely alter the conditions in the headwaters of high-mountain rivers. One of the potential implications of this change is an increase in frequency and magnitude of outburst floods - highly dynamic flows capable of carrying large amounts of water and sediments. Sudden outbursts from lakes formed behind natural dams are complex geomorphological processes and are often part of a hazard cascade. In contrast to other types of natural hazards in high-alpine areas, for example landslides or avalanches, outburst floods are highly infrequent. Therefore, observations and data describing for example the mode of outburst or the hydraulic properties of the downstream propagating flow are very limited, which is a major challenge in contemporary (glacial) lake outburst flood research. Although glacial lake outburst floods (GLOFs) and landslide-dammed lake outburst floods (LLOFs) are rare, a number of documented events caused high fatality counts and damage. The highest documented losses due to outburst floods since the start of the 20th century were induced by only a few high-discharge events. Thus, outburst floods can be a significant hazard to downvalley communities and infrastructure in high-mountain regions worldwide. This thesis focuses on the Greater Himalayan region, a vast mountain belt stretching across 0.89 million km2. Although potentially hundreds of outburst floods have occurred there since the beginning of the 20th century, data on these events is still scarce. Projections of cryospheric change, including glacier-mass wastage and permafrost degradation, will likely result in an overall increase of the water volume stored in meltwater lakes as well as the destabilisation of mountain slopes in the Greater Himalayan region. Thus, the potential for outburst floods to affect the increasingly more densely populated valleys of this mountain belt is also likely to increase in the future. A prime example of one of these valleys is the Pokhara valley in Nepal, which is drained by the Seti Khola, a river crossing one of the steepest topographic gradients in the Himalayas. This valley is also home to Nepal's second largest, rapidly growing city, Pokhara, which currently has a population of more than half a million people - some of which live in informal settlements within the floodplain of the Seti Khola. Although there is ample evidence for past outburst floods along this river in recent and historic times, these events have hardly been quantified. The main motivation of my thesis is to address the data scarcity on past and potential future outburst floods in the Greater Himalayan region, both at a regional and at a local scale. For the former, I compiled an inventory of >3,000 moraine-dammed lakes, of which about 1\% had a documented sudden failure in the past four decades. I used this data to test whether a number of predictors that have been widely applied in previous GLOF assessments are statistically relevant when estimating past GLOF susceptibility. For this, I set up four Bayesian multi-level logistic regression models, in which I explored the credibility of the predictors lake area, lake-area dynamics, lake elevation, parent-glacier-mass balance, and monsoonality. By using a hierarchical approach consisting of two levels, this probabilistic framework also allowed for spatial variability on GLOF susceptibility across the vast study area, which until now had not been considered in studies of this scale. The model results suggest that in the Nyainqentanglha and Eastern Himalayas - regions with strong negative glacier-mass balances - lakes have been more prone to release GLOFs than in regions with less negative or even stable glacier-mass balances. Similarly, larger lakes in larger catchments had, on average, a higher probability to have had a GLOF in the past four decades. Yet, monsoonality, lake elevation, and lake-area dynamics were more ambiguous. This challenges the credibility of a lake's rapid growth in surface area as an indicator of a pending outburst; a metric that has been applied to regional GLOF assessments worldwide. At a local scale, my thesis aims to overcome data scarcity concerning the flow characteristics of the catastrophic May 2012 flood along the Seti Khola, which caused 72 fatalities, as well as potentially much larger predecessors, which deposited >1 km³ of sediment in the Pokhara valley between the 12th and 14th century CE. To reconstruct peak discharges, flow depths, and flow velocities of the 2012 flood, I mapped the extents of flood sediments from RapidEye satellite imagery and used these as a proxy for inundation limits. To constrain the latter for the Mediaeval events, I utilised outcrops of slackwater deposits in the fills of tributary valleys. Using steady-state hydrodynamic modelling for a wide range of plausible scenarios, from meteorological (1,000 m³ s-1) to cataclysmic outburst floods (600,000 m³ s-1), I assessed the likely initial discharges of the recent and the Mediaeval floods based on the lowest mismatch between sedimentary evidence and simulated flood limits. One-dimensional HEC-RAS simulations suggest, that the 2012 flood most likely had a peak discharge of 3,700 m³ s-1 in the upper Seti Khola and attenuated to 500 m³ s-1 when arriving in Pokhara's suburbs some 15 km downstream. Simulations of flow in two-dimensions with orders of magnitude higher peak discharges in ANUGA show extensive backwater effects in the main tributary valleys. These backwater effects match the locations of slackwater deposits and, hence, attest for the flood character of Mediaeval sediment pulses. This thesis provides first quantitative proof for the hypothesis, that the latter were linked to earthquake-triggered outbursts of large former lakes in the headwaters of the Seti Khola - producing floods with peak discharges of >50,000 m³ s-1. Building on this improved understanding of past floods along the Seti Khola, my thesis continues with an analysis of the impacts of potential future outburst floods on land cover, including built-up areas and infrastructure mapped from high-resolution satellite and OpenStreetMap data. HEC-RAS simulations of ten flood scenarios, with peak discharges ranging from 1,000 to 10,000 m³ s-1, show that the relative inundation hazard is highest in Pokhara's north-western suburbs. There, the potential effects of hydraulic ponding upstream of narrow gorges might locally sustain higher flow depths. Yet, along this reach, informal settlements and gravel mining activities are close to the active channel. By tracing the construction dynamics in two of these potentially affected informal settlements on multi-temporal RapidEye, PlanetScope, and Google Earth imagery, I found that exposure increased locally between three- to twentyfold in just over a decade (2008 to 2021). In conclusion, this thesis provides new quantitative insights into the past controls on the susceptibility of glacial lakes to sudden outburst at a regional scale and the flow dynamics of propagating flood waves released by past events at a local scale, which can aid future hazard assessments on transient scales in the Greater Himalayan region. My subsequent exploration of the impacts of potential future outburst floods to exposed infrastructure and (informal) settlements might provide valuable inputs to anticipatory assessments of multiple risks in the Pokhara valley.},
  language  = {en}
}
@article{NorrisCarvalhoJonesetal.2017,
  author    = {Norris, Jesse and Carvalho, Leila M. V. and Jones, Charles and Cannon, Forest and Bookhagen, Bodo and Palazzi, Elisa and Tahir, Adnan Ahmad},
  title     = {The spatiotemporal variability of precipitation over the Himalaya: evaluation of one-year WRF model simulation},
  series = {Climate dynamics : observational, theoretical and computational research on the climate system},
  volume    = {49},
  journal   = {Climate dynamics : observational, theoretical and computational research on the climate system},
  publisher = {Springer},
  address   = {New York},
  issn      = {0930-7575},
  doi       = {10.1007/s00382-016-3414-y},
  pages     = {2179 -- 2204},
  year      = {2017},
  abstract  = {The Weather Research and Forecasting (WRF) model is used to simulate the spatiotemporal distribution of precipitation over central Asia over the year April 2005 through March 2006. Experiments are performed at 6.7 km horizontal grid spacing, with an emphasis on winter and summer precipitation over the Himalaya. The model and the Tropical Rainfall Measuring Mission show a similar inter-seasonal cycle of precipitation, from extratropical cyclones to monsoon precipitation, with agreement also in the diurnal cycle of monsoon precipitation. In winter months, WRF compares better in timeseries of daily precipitation to stations below than above 3-km elevation, likely due to inferior measurement of snow than rain by the stations, highlighting the need for reliable snowfall measurements at high elevations in winter. In summer months, the nocturnal precipitation cycle in the foothills and valleys of the Himalaya is captured by this 6.7-km WRF simulation, while coarser simulations with convective parameterization show near zero nocturnal precipitation. In winter months, higher resolution is less important, serving only to slightly increase precipitation magnitudes due to steeper slopes. However, even in the 6.7-km simulation, afternoon precipitation is overestimated at high elevations, which can be reduced by even higher-resolution (2.2-km) simulations. These results indicate that WRF provides skillful simulations of precipitation relevant for studies of water resources over the complex terrain in the Himalaya.},
  language  = {en}
}
@article{SchwanghartWorniHuggeletal.2016,
  author    = {Schwanghart, Wolfgang and Worni, Raphael and Huggel, Christian and Stoffel, Markus and Korup, Oliver},
  title     = {Uncertainty in the Himalayan energy-water nexus: estimating regional exposure to glacial lake outburst floods},
  series = {Environmental research letters},
  volume    = {11},
  journal   = {Environmental research letters},
  publisher = {IOP Publ. Ltd.},
  address   = {Bristol},
  issn      = {1748-9326},
  doi       = {10.1088/1748-9326/11/7/074005},
  pages     = {9},
  year      = {2016},
  abstract  = {Himalayan water resources attract a rapidly growing number of hydroelectric power projects (HPP) to satisfy Asia's soaring energy demands. Yet HPP operating or planned in steep, glacier-fed mountain rivers face hazards of glacial lake outburst floods (GLOFs) that can damage hydropower infrastructure, alter water and sediment yields, and compromise livelihoods downstream. Detailed appraisals of such GLOF hazards are limited to case studies, however, and a more comprehensive, systematic analysis remains elusive. To this end we estimate the regional exposure of 257 Himalayan HPP to GLOFs, using a flood-wave propagation model fed by Monte Carlo-derived outburst volumes of >2300 glacial lakes. We interpret the spread of thus modeled peak discharges as a predictive uncertainty that arises mainly from outburst volumes and dam-breach rates that are difficult to assess before dams fail. With 66\% of sampled HPP are on potential GLOF tracks, up to one third of these HPP could experience GLOF discharges well above local design floods, as hydropower development continues to seek higher sites closer to glacial lakes. We compute that this systematic push of HPP into headwaters effectively doubles the uncertainty about GLOF peak discharge in these locations. Peak discharges farther downstream, in contrast, are easier to predict because GLOF waves attenuate rapidly. Considering this systematic pattern of regional GLOF exposure might aid the site selection of future Himalayan HPP. Our method can augment, and help to regularly update, current hazard assessments, given that global warming is likely changing the number and size of Himalayan meltwater lakes.},
  language  = {en}
}
@article{StruckAndermannHoviusetal.2015,
  author    = {Struck, Martin and Andermann, Christoff and Hovius, Niels and Korup, Oliver and Turowski, Jens M. and Bista, Raj and Pandit, Hari P. and Dahal, Ranjan K.},
  title     = {Monsoonal hillslope processes determine grain size-specific suspended sediment fluxes in a trans-Himalayan river},
  series = {Geophysical research letters},
  volume    = {42},
  journal   = {Geophysical research letters},
  number    = {7},
  publisher = {American Geophysical Union},
  address   = {Washington},
  issn      = {0094-8276},
  doi       = {10.1002/2015GL063360},
  pages     = {2302 -- 2308},
  year      = {2015},
  abstract  = {Sediments in rivers record the dynamics of erosion processes. While bulk sediment fluxes are easily and routinely obtained, sediment caliber remains underexplored when inferring erosion mechanisms. Yet sediment grain size distributions may be the key to discriminating their origin. We have studied grain size-specific suspended sediment fluxes in the Kali Gandaki, a major trans-Himalayan river. Two strategically located gauging stations enable tracing of sediment caliber on either side of the Himalayan orographic barrier. The data show that fine sediment input into the northern headwaters is persistent, while coarse sediment comes from the High Himalayas during the summer monsoon. A temporally matching landslide inventory similarly indicates the prominence of monsoon-driven hillslope mass wasting. Thus, mechanisms of sediment supply can leave strong traces in the fluvial caliber, which could project well beyond the mountain front and add to the variability of the sedimentary record of orogen erosion.},
  language  = {en}
}
@article{AndermannCraveGloaguenetal.2012,
  author    = {Andermann, Christoff and Crave, Alain and Gloaguen, Richard and Davy, Philippe and Bonnet, Stephane},
  title     = {Connecting source and transport: Suspended sediments in the Nepal Himalayas},
  series = {Earth \& planetary science letters},
  volume    = {351},
  journal   = {Earth \& planetary science letters},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0012-821X},
  doi       = {10.1016/j.epsl.2012.06.059},
  pages     = {158 -- 170},
  year      = {2012},
  abstract  = {Understanding the dynamics of sediment fluxes is a key issue to constrain modern erosion rates in mountain belts and determine the still debated level of control exerted by precipitation, topography and tectonics. The well defined monsoon seasonality in the Himalayas, together with active tectonics and strong relief provide an ideal environment to assess these possible interactions. For this purpose, we present a new compilation of daily suspended sediment data for 12 stations of the major rivers of the Nepal Himalayas. We analyze the relationships of sediment transport with daily river discharge and precipitation data as well as with morphometric parameters. We show that suspended sediment concentrations vary systematically through the seasons and asynchronously to river discharge displaying a hysteresis effect. This clockwise hysteresis effect disappears when suspended sediment fluxes are directly compared with direct storm discharge. Therefore we attribute the hysteresis effect to groundwater dilution rather than a sediment supply limitation. We infer a rating model to calculate erosion rates directly from long river discharge chronicles. We show that, when normalized by drainage area and mean sediment flux, all rivers exhibit the same trend. This similarity implies that all river basins have the same erosion behavior, independent of location, size and catchment characteristics. Erosion rates calculated from suspended sediment fluxes range between 0.1 and 2.8 mm/yr. The erosion rates of the three main basins of Nepal are in the range 0.9-1.5 mm/yr. Erosion rates in the Higher Himalayas are relatively low ( <0.5 mm/yr, except for Kali Gandaki), while in the Lesser Himalayas they range from 0.2 to 2 mm/yr. We propose that material transport in the rivers depends on hillslope sediment supply, which is, in turn, controlled by those rainfalls producing direct runoff. In other words, the rivers in the Nepal Himalayas are supply-limited and the hillsopes as a contributing source are transport-limited. We also show that erosion processes are not as much controlled by infrequently occurring extreme precipitation events, than by moderate ones with a high recurrence interval.},
  language  = {en}
}
@article{BloetheKorup2013,
  author    = {Bl{\"o}the, Jan Henrik and Korup, Oliver},
  title     = {Millennial lag times in the Himalayan sediment routing system},
  series = {Earth \& planetary science letters},
  volume    = {382},
  journal   = {Earth \& planetary science letters},
  number    = {20},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0012-821X},
  doi       = {10.1016/j.epsl.2013.08.044},
  pages     = {38 -- 46},
  year      = {2013},
  abstract  = {Any understanding of sediment routing from mountain belts to their forelands and offshore sinks remains incomplete without estimates of intermediate storage that decisively buffers sediment yields from erosion rates, attenuates water and sediment fluxes, and protects underlying bedrock from incision. We quantify for the first time the sediment stored in > 38000 mainly postglacial Himalayan valley fills, based on an empirical volume-area scaling of valley-fill outlines automatically extracted from digital topographic data. The estimated total volume of 690(+452/-242) km(3) is mostly contained in few large valley fills > 1 km(3), while catastrophic mass wasting adds another 177(31) km(3). Sediment storage volumes are highly disparate along the strike of the orogen. Much of the Himalaya's stock of sediment is sequestered in glacially scoured valleys that provide accommodation space for similar to 44\% of the total volume upstream of the rapidly exhuming and incising syntaxes. Conversely, the step-like long-wave topography of the central Himalayas limits glacier extent, and thus any significant glacier-derived storage of sediment away from tectonic basins. We show that exclusive removal of Himalayan valley fills could nourish contemporary sediment flux from the Indus and Brahmaputra basins for > 1 kyr, though individual fills may attain residence times of > 100 kyr. These millennial lag times in the Himalayan sediment routing system may sufficiently buffer signals of short-term seismic as well as climatic disturbances, thus complicating simple correlation and interpretation of sedimentary archives from the Himalayan orogen, its foreland, and its submarine fan systems. (C) 2013 Elsevier B.V. All rights reserved.},
  language  = {en}
}
@misc{SchwanghartWorniHuggeletal.2016,
  author    = {Schwanghart, Wolfgang and Worni, Raphael and Huggel, Christian and Stoffel, Markus and Korup, Oliver},
  title     = {Uncertainty in the Himalayan energy-water nexus},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-97136},
  pages     = {9},
  year      = {2016},
  abstract  = {Himalayan water resources attract a rapidly growing number of hydroelectric power projects (HPP) to satisfy Asia's soaring energy demands. Yet HPP operating or planned in steep, glacier-fed mountain rivers face hazards of glacial lake outburst floods (GLOFs) that can damage hydropower infrastructure, alter water and sediment yields, and compromise livelihoods downstream. Detailed appraisals of such GLOF hazards are limited to case studies, however, and a more comprehensive, systematic analysis remains elusive. To this end we estimate the regional exposure of 257 Himalayan HPP to GLOFs, using a flood-wave propagation model fed by Monte Carlo-derived outburst volumes of >2300 glacial lakes. We interpret the spread of thus modeled peak discharges as a predictive uncertainty that arises mainly from outburst volumes and dam-breach rates that are difficult to assess before dams fail. With 66\% of sampled HPP are on potential GLOF tracks, up to one third of these HPP could experience GLOF discharges well above local design floods, as hydropower development continues to seek higher sites closer to glacial lakes. We compute that this systematic push of HPP into headwaters effectively doubles the uncertainty about GLOF peak discharge in these locations. Peak discharges farther downstream, in contrast, are easier to predict because GLOF waves attenuate rapidly. Considering this systematic pattern of regional GLOF exposure might aid the site selection of future Himalayan HPP. Our method can augment, and help to regularly update, current hazard assessments, given that global warming is likely changing the number and size of Himalayan meltwater lakes.},
  language  = {en}
}
@article{SchwanghartWorniHuggeletal.2016,
  author    = {Schwanghart, Wolfgang and Worni, Raphael and Huggel, Christian and Stoffel, Markus and Korup, Oliver},
  title     = {Uncertainty in the Himalayan energy-water nexus},
  series = {Environmental research letters : ERL},
  volume    = {11},
  journal   = {Environmental research letters : ERL},
  publisher = {IOP Publ.},
  address   = {Bristol},
  issn      = {1748-9326},
  doi       = {10.1088/1748-9326/11/7/074005},
  pages     = {9},
  year      = {2016},
  abstract  = {Himalayan water resources attract a rapidly growing number of hydroelectric power projects (HPP) to satisfy Asia's soaring energy demands. Yet HPP operating or planned in steep, glacier-fed mountain rivers face hazards of glacial lake outburst floods (GLOFs) that can damage hydropower infrastructure, alter water and sediment yields, and compromise livelihoods downstream. Detailed appraisals of such GLOF hazards are limited to case studies, however, and a more comprehensive, systematic analysis remains elusive. To this end we estimate the regional exposure of 257 Himalayan HPP to GLOFs, using a flood-wave propagation model fed by Monte Carlo-derived outburst volumes of >2300 glacial lakes. We interpret the spread of thus modeled peak discharges as a predictive uncertainty that arises mainly from outburst volumes and dam-breach rates that are difficult to assess before dams fail. With 66\% of sampled HPP are on potential GLOF tracks, up to one third of these HPP could experience GLOF discharges well above local design floods, as hydropower development continues to seek higher sites closer to glacial lakes. We compute that this systematic push of HPP into headwaters effectively doubles the uncertainty about GLOF peak discharge in these locations. Peak discharges farther downstream, in contrast, are easier to predict because GLOF waves attenuate rapidly. Considering this systematic pattern of regional GLOF exposure might aid the site selection of future Himalayan HPP. Our method can augment, and help to regularly update, current hazard assessments, given that global warming is likely changing the number and size of Himalayan meltwater lakes.},
  language  = {en}
}