@article{BufeTurowskiBurbanketal.2019,
  author    = {Bufe, Aaron and Turowski, Jens M. and Burbank, Douglas W. and Paola, Chris and Wickert, Andrew D. and Tofelde, Stefanie},
  title     = {Controls on the lateral channel-migration rate of braided channel systems in coarse non-cohesive sediment},
  series = {Earth surface processes and landforms : the journal of the British Geomorphological Research Group},
  volume    = {44},
  journal   = {Earth surface processes and landforms : the journal of the British Geomorphological Research Group},
  number    = {14},
  publisher = {Wiley},
  address   = {Hoboken},
  issn      = {0197-9337},
  doi       = {10.1002/esp.4710},
  pages     = {2823 -- 2836},
  year      = {2019},
  abstract  = {Lateral movements of alluvial river channels control the extent and reworking rates of alluvial fans, floodplains, deltas, and alluvial sections of bedrock rivers. These lateral movements can occur by gradual channel migration or by sudden changes in channel position (avulsions). Whereas models exist for rates of river avulsion, we lack a detailed understanding of the rates of lateral channel migration on the scale of a channel belt. In a two-step process, we develop here an expression for the lateral migration rate of braided channel systems in coarse, non-cohesive sediment. On the basis of photographic and topographic data from laboratory experiments of braided channels performed under constant external boundary conditions, we first explore the impact of autogenic variations of the channel-system geometry (i.e. channel-bank heights, water depths, channel-system width, and channel slope) on channel-migration rates. In agreement with theoretical expectations, we find that, under such constant boundary conditions, the laterally reworked volume of sediment is constant and lateral channel-migration rates scale inversely with the channel-bank height. Furthermore, when channel-bank heights are accounted for, lateral migration rates are independent of the remaining channel geometry parameters. These constraints allow us, in a second step, to derive two alternative expressions for lateral channel-migration rates under different boundary conditions using dimensional analysis. Fits of a compilation of laboratory experiments to these expressions suggest that, for a given channel bank-height, migration rates are strongly sensitive to water discharges and more weakly sensitive to sediment discharges. In addition, external perturbations, such as changes in sediment and water discharges or base level fall, can indirectly affect lateral channel-migration rates by modulating channel-bank heights.},
  language  = {en}
}
@article{CookTurowskiHovius2020,
  author    = {Cook, Kristen L. and Turowski, Jens M. and Hovius, Niels},
  title     = {Width control on event-scale deposition and evacuation of sediment in bedrock-confined channels},
  series = {Earth surface processes and landforms : the journal of the British Geomorphological Research Group},
  volume    = {45},
  journal   = {Earth surface processes and landforms : the journal of the British Geomorphological Research Group},
  number    = {14},
  publisher = {Wiley},
  address   = {Hoboken},
  issn      = {0197-9337},
  doi       = {10.1002/esp.4993},
  pages     = {3702 -- 3713},
  year      = {2020},
  abstract  = {In mixed bedrock-alluvial rivers, the response of the system to a flood event can be affected by a number of factors, including coarse sediment availability in the channel, sediment supply from the hillslopes and upstream, flood sequencing and coarse sediment grain size distribution. However, the impact of along-stream changes in channel width on bedload transport dynamics remains largely unexplored. We combine field data, theory and numerical modelling to address this gap. First, we present observations from the Daan River gorge in western Taiwan, where the river flows through a 1 km long 20-50 m wide bedrock gorge bounded upstream and downstream by wide braidplains. We documented two flood events during which coarse sediment evacuation and redeposition appear to cause changes of up to several metres in channel bed elevation. Motivated by this case study, we examined the relationships between discharge, channel width and bedload transport capacity, and show that for a given slope narrow channels transport bedload more efficiently than wide ones at low discharges, whereas wider channels are more efficient at high discharges. We used the model sedFlow to explore this effect, running a random sequence of floods through a channel with a narrow gorge section bounded upstream and downstream by wider reaches. Channel response to imposed floods is complex, as high and low discharges drive different spatial patterns of erosion and deposition, and the channel may experience both of these regimes during the peak and recession periods of each flood. Our modelling suggests that width differences alone can drive substantial variations in sediment flux and bed response, without the need for variations in sediment supply or mobility. The fluctuations in sediment transport rates that result from width variations can lead to intermittent bed exposure, driving incision in different segments of the channel during different portions of the hydrograph.},
  language  = {en}
}
@article{GollyTurowskiBadouxetal.2017,
  author    = {Golly, Antonius and Turowski, Jens M. and Badoux, Alexandre and Hovius, Niels},
  title     = {Controls and feedbacks in the coupling of mountain channels and hillslopes},
  series = {Geology},
  volume    = {45},
  journal   = {Geology},
  publisher = {Geological Society of America},
  address   = {Boulder},
  issn      = {0091-7613},
  doi       = {10.1130/G38831.1},
  pages     = {307 -- 310},
  year      = {2017},
  abstract  = {Mountain channels can be strongly coupled with adjacent hillslopes, exchanging both mass and energy. However, hypotheses of the underlying cause and effect relations are based on indirect observations that do not resolve the mechanics of channel-hillslope coupling at the process scale. Here we present direct observational data of a coupled channel-hillslope system in the catchment area of the Erlenbach, a mountain stream in Switzerland. A slow-moving landslide flanking this alpine stream failed after a flood had eroded an alluvial step in the channel at its base, representing evidence for an upsystem link in channel-hillslope coupling. Progressive accumulation of landslide debris in the channel resulted in a renewed step, stabilizing the hillslope and restoring the channel step in a downsystem link. Thus, upsystem and downsystem coupling mechanisms are joined in a negative feedback cycle. In this cycle, debuttressing and rebuttressing due to channel bed erosion and alluviation are the dominant controls on hillslope stability. Based on an order of magnitude estimate it is plausible that the observed feedback mechanism is a relevant process in the production of coarse (>2 mm) sediment in the Erlenbach.},
  language  = {en}
}
@misc{MarcBehlingAndermannetal.2019,
  author    = {Marc, Odin and Behling, Robert and Andermann, Christoff and Turowski, Jens M. and Illien, Luc and Roessner, Sigrid and Hovius, Niels},
  title     = {Long-term erosion of the Nepal Himalayas by bedrock landsliding},
  series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  number    = {646},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-42502},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-425022},
  pages     = {22},
  year      = {2019},
  abstract  = {In active mountain belts with steep terrain, bedrock landsliding is a major erosional agent. In the Himalayas, landsliding is driven by annual hydro-meteorological forcing due to the summer monsoon and by rarer, exceptional events, such as earthquakes. Independent methods yield erosion rate estimates that appear to increase with sampling time, suggesting that rare, high-magnitude erosion events dominate the erosional budget. Nevertheless, until now, neither the contribution of monsoon and earthquakes to landslide erosion nor the proportion of erosion due to rare, giant landslides have been quantified in the Himalayas. We address these challenges by combining and analysing earthquake- and monsoon-induced landslide inventories across different timescales. With time series of 5 m satellite images over four main valleys in central Nepal, we comprehensively mapped landslides caused by the monsoon from 2010 to 2018. We found no clear correlation between monsoon properties and landsliding and a similar mean landsliding rate for all valleys, except in 2015, where the valleys affected by the earthquake featured ∼ 5-8 times more landsliding than the pre-earthquake mean rate. The longterm size-frequency distribution of monsoon-induced landsliding (MIL) was derived from these inventories and from an inventory of landslides larger than ∼ 0.1 km 2 that occurred between 1972 and 2014. Using a published landslide inventory for the Gorkha 2015 earthquake, we derive the size-frequency distribution for earthquake-induced landsliding (EQIL). These two distributions are dominated by infrequent, large and giant landslides but under-predict an estimated Holocene frequency of giant landslides (> 1 km 3 ) which we derived from a literature compilation. This discrepancy can be resolved when modelling the effect of a full distribution of earthquakes of variable magnitude and when considering that a shallower earthquake may cause larger landslides. In this case, EQIL and MIL contribute about equally to a total long-term erosion of ∼ 2 ± 0.75 mm yr -1 in agreement with most thermo-chronological data. Independently of the specific total and relative erosion rates, the heavy-tailed size-frequency distribution from MIL and EQIL and the very large maximal landslide size in the Himalayas indicate that mean landslide erosion rates increase with sampling time, as has been observed for independent erosion estimates. Further, we find that the sampling timescale required to adequately capture the frequency of the largest landslides, which is necessary for deriving long-term mean erosion rates, is often much longer than the averaging time of cosmogenic 10 Be methods. This observation presents a strong caveat when interpreting spatial or temporal variability in erosion rates from this method. Thus, in areas where a very large, rare landslide contributes heavily to long-term erosion (as the Himalayas), we recommend 10 Be sample in catchments with source areas > 10 000 km 2 to reduce the method mean bias to below ∼ 20 \% of the long-term erosion.},
  language  = {en}
}
@article{MarcBehlingAndermannetal.2019,
  author    = {Marc, Odin and Behling, Robert and Andermann, Christoff and Turowski, Jens M. and Illien, Luc and Roessner, Sigrid and Hovius, Niels},
  title     = {Long-term erosion of the Nepal Himalayas by bedrock landsliding},
  series = {Earth surface dynamics},
  volume    = {7},
  journal   = {Earth surface dynamics},
  number    = {1},
  publisher = {Copernicus},
  address   = {G{\"o}ttingen},
  issn      = {2196-6311},
  doi       = {10.5194/esurf-7-107-2019},
  pages     = {107 -- 128},
  year      = {2019},
  abstract  = {In active mountain belts with steep terrain, bedrock landsliding is a major erosional agent. In the Himalayas, landsliding is driven by annual hydro-meteorological forcing due to the summer monsoon and by rarer, exceptional events, such as earthquakes. Independent methods yield erosion rate estimates that appear to increase with sampling time, suggesting that rare, high-magnitude erosion events dominate the erosional budget. Nevertheless, until now, neither the contribution of monsoon and earthquakes to landslide erosion nor the proportion of erosion due to rare, giant landslides have been quantified in the Himalayas. We address these challenges by combining and analysing earthquake- and monsoon-induced landslide inventories across different timescales. With time series of 5 m satellite images over four main valleys in central Nepal, we comprehensively mapped landslides caused by the monsoon from 2010 to 2018. We found no clear correlation between monsoon properties and landsliding and a similar mean landsliding rate for all valleys, except in 2015, where the valleys affected by the earthquake featured similar to 5-8 times more landsliding than the pre-earthquake mean rate. The longterm size-frequency distribution of monsoon-induced landsliding (MIL) was derived from these inventories and from an inventory of landslides larger than similar to 0.1 km(2) that occurred between 1972 and 2014. Using a published landslide inventory for the Gorkha 2015 earthquake, we derive the size-frequency distribution for earthquakeinduced landsliding (EQIL). These two distributions are dominated by infrequent, large and giant landslides but under-predict an estimated Holocene frequency of giant landslides (> 1 km(3)) which we derived from a literature compilation. This discrepancy can be resolved when modelling the effect of a full distribution of earthquakes of variable magnitude and when considering that a shallower earthquake may cause larger landslides. In this case, EQIL and MIL contribute about equally to a total long-term erosion of similar to 2 +/- 0.75 mm yr(-1) in agreement with most thermo-chronological data. Independently of the specific total and relative erosion rates, the heavy-tailed size-frequency distribution from MIL and EQIL and the very large maximal landslide size in the Himalayas indicate that mean landslide erosion rates increase with sampling time, as has been observed for independent erosion estimates. Further, we find that the sampling timescale required to adequately capture the frequency of the largest landslides, which is necessary for deriving long-term mean erosion rates, is often much longer than the averaging time of cosmogenic Be-10 methods. This observation presents a strong caveat when interpreting spatial or temporal variability in erosion rates from this method. Thus, in areas where a very large, rare landslide contributes heavily to long-term erosion (as the Himalayas), we recommend Be-10 sample in catchments with source areas > 10 000 km(2) to reduce the method mean bias to below similar to 20 \% of the long-term erosion.},
  language  = {en}
}
@article{NativTurowski2020,
  author    = {Nativ, Ron and Turowski, Jens M.},
  title     = {Site dependence of fluvial incision rate scaling with timescale},
  series = {Journal of geophysical research : Earth surface},
  volume    = {125},
  journal   = {Journal of geophysical research : Earth surface},
  number    = {11},
  publisher = {American Geophysical Union},
  address   = {Washington},
  issn      = {2169-9003},
  doi       = {10.1029/2020JF005808},
  pages     = {21},
  year      = {2020},
  abstract  = {Global measurements of incision rate typically show a negative scaling with the timescale over which they were averaged, a phenomenon referred to as the "Sadler effect." This time dependency is thought to result from hiatus periods between incision phases, which leads to a power law scaling of incision rate with timescale. Alternatively, the "Sadler effect" has been argued to be a consequence of the mobility of the modern river bed, where the timescale dependency of incision rates arises from a bias due to the choice of the reference system. In this case, incision rates should be independent of the timescale, provided that the correct reference system is chosen. It is unclear which model best explains the "Sadler effect," and, if a timescale dependency exists, which mathematical formulation can be used to describe it. Here, we present a compilation of 581 bedrock incision rates from 34 studies, averaged over timescales ranging from single floods to millions of years. We constrain the functional relationship between incision rate and timescale and show that time-independent incision rate is inconsistent with the global data. Using a power law dependence, a single constant power is inconsistent with the distribution of observed exponents. Therefore, the scaling exponent is site dependent. Consequently, incision rates measured over contrasting timescales cannot be meaningfully compared between different field sites without properly considering the "Sadler effect." We explore the controls on the variable exponents and propose an empirical equation to correct observed incision rates for their timescale dependency.},
  language  = {en}
}
@article{ScheingrossHoviusDellingeretal.2019,
  author    = {Scheingross, Joel S. and Hovius, Niels and Dellinger, M. and Hilton, R. G. and Repasch, M. and Sachse, Dirk and Grocke, D. R. and Vieth-Hillebrand, Andrea and Turowski, Jens M.},
  title     = {Preservation of organic carbon during active fluvial transport and particle abrasion},
  series = {Geology},
  volume    = {47},
  journal   = {Geology},
  number    = {10},
  publisher = {American Institute of Physics},
  address   = {Boulder},
  issn      = {0091-7613},
  doi       = {10.1130/G46442.1},
  pages     = {958 -- 962},
  year      = {2019},
  abstract  = {Oxidation of particulate organic carbon (POC) during fluvial transit releases CO2 to the atmosphere and can influence global climate. Field data show large POC oxidation fluxes in lowland rivers; however, it is unclear if POC losses occur predominantly during in-river transport, where POC is in continual motion within an aerated environment, or during transient storage in floodplains, which may be anoxic. Determination of the locus of POC oxidation in lowland rivers is needed to develop process-based models to predict POC losses, constrain carbon budgets, and unravel links between climate and erosion. However, sediment exchange between rivers and floodplains makes differentiating POC oxidation during in-river transport from oxidation during floodplain storage difficult. Here, we isolated inriver POC oxidation using flume experiments transporting petrogenic and biospheric POC without floodplain storage. Our experiments showed solid phase POC losses of 0\%-10\% over similar to 10(3) km of fluvial transport, compared to similar to 7\% to >50\% losses observed in rivers over similar distances. The production of dissolved organic carbon (DOC) and dissolved rhenium (a proxy for petrogenic POC oxidation) was consistent with small POC lasses, and replicate experiments in static water tanks gave similar results. Our results show that fluvial sediment transport, particle abrasion, and turbulent mixing have a minimal role on POC oxidation, and they suggest that POC losses may accrue primarily in floodplain storage.},
  language  = {en}
}
@article{SchoepaChaoLipovskyetal.2018,
  author    = {Sch{\"o}pa, Anne and Chao, Wei-An and Lipovsky, Bradley P. and Hovius, Niels and White, Robert S. and Green, Robert G. and Turowski, Jens M.},
  title     = {Dynamics of the Askja caldera July 2014 landslide, Iceland, from seismic signal analysis},
  series = {Earth surface dynamics},
  volume    = {6},
  journal   = {Earth surface dynamics},
  number    = {2},
  publisher = {Copernicus},
  address   = {G{\"o}ttingen},
  issn      = {2196-6311},
  doi       = {10.5194/esurf-6-467-2018},
  pages     = {467 -- 485},
  year      = {2018},
  abstract  = {Landslide hazard motivates the need for a deeper understanding of the events that occur before, during, and after catastrophic slope failures. Due to the destructive nature of such events, in situ observation is often difficult or impossible. Here, we use data from a network of 58 seismic stations to characterise a large landslide at the Askja caldera, Iceland, on 21 July 2014. High data quality and extensive network coverage allow us to analyse both long- and short-period signals associated with the landslide, and thereby obtain information about its triggering, initiation, timing, and propagation. At long periods, a landslide force history inversion shows that the Askja landslide was a single, large event starting at the SE corner of the caldera lake at 23:24:05 UTC and propagating to the NW in the following 2 min The bulk sliding mass was 7-16 x 10(10) kg, equivalent to a collapsed volume of 35-80 x 10(6) m(3). The sliding mass was displaced downslope by 1260 +/- 250 m. At short periods, a seismic tremor was observed for 30 min before the landslide. The tremor is approximately harmonic with a fundamental frequency of 2.3 Hz and shows time-dependent changes of its frequency content. We attribute the seismic tremor to stick-slip motion along the landslide failure plane. Accelerating motion leading up to the catastrophic slope failure culminated in an aseismic quiescent period for 2 min before the landslide. We propose that precursory seismic signals may be useful in landslide early-warning systems. The 8 h after the main landslide failure are characterised by smaller slope failures originating from the destabilised caldera wall decaying in frequency and magnitude. We introduce the term "afterslides" for this subsequent, declining slope activity after a large landslide.},
  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{TofeldeBufeTurowski2022,
  author    = {Tofelde, Stefanie and Bufe, Aaron and Turowski, Jens M.},
  title     = {Hillslope Sediment Supply Limits Alluvial Valley Width},
  series = {AGU Advances},
  journal   = {AGU Advances},
  publisher = {American Geophysical Union (AGU); Wiley},
  address   = {Hoboken, New Jersey, USA},
  issn      = {2576-604X},
  doi       = {10.1029/2021AV000641},
  pages     = {20},
  year      = {2022},
  abstract  = {River-valley morphology preserves information on tectonic and climatic conditions that shape landscapes. Observations suggest that river discharge and valley-wall lithology are the main controls on valley width. Yet, current models based on these observations fail to explain the full range of cross-sectional valley shapes in nature, suggesting hitherto unquantified controls on valley width. In particular, current models cannot explain the existence of paired terrace sequences that form under cyclic climate forcing. Paired river terraces are staircases of abandoned floodplains on both valley sides, and hence preserve past valley widths. Their formation requires alternating phases of predominantly river incision and predominantly lateral planation, plus progressive valley narrowing. While cyclic Quaternary climate changes can explain shifts between incision and lateral erosion, the driving mechanism of valley narrowing is unknown. Here, we extract valley geometries from climatically formed, alluvial river-terrace sequences and show that across our dataset, the total cumulative terrace height (here: total valley height) explains 90\%-99\% of the variance in valley width at the terrace sites. This finding suggests that valley height, or a parameter that scales linearly with valley height, controls valley width in addition to river discharge and lithology. To explain this valley-width-height relationship, we reformulate existing valley-width models and suggest that, when adjusting to new boundary conditions, alluvial valleys evolve to a width at which sediment removal from valley walls matches lateral sediment supply from hillslope erosion. Such a hillslope-channel coupling is not captured in current valley-evolution models. Our model can explain the existence of paired terrace sequences under cyclic climate forcing and relates valley width to measurable field parameters. Therefore, it facilitates the reconstruction of past climatic and tectonic conditions from valley topography.},
  language  = {en}
}
@misc{TofeldeBufeTurowski2022,
  author    = {Tofelde, Stefanie and Bufe, Aaron and Turowski, Jens M.},
  title     = {Hillslope Sediment Supply Limits Alluvial Valley Width},
  series = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  number    = {1289},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-57287},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-572879},
  pages     = {20},
  year      = {2022},
  abstract  = {River-valley morphology preserves information on tectonic and climatic conditions that shape landscapes. Observations suggest that river discharge and valley-wall lithology are the main controls on valley width. Yet, current models based on these observations fail to explain the full range of cross-sectional valley shapes in nature, suggesting hitherto unquantified controls on valley width. In particular, current models cannot explain the existence of paired terrace sequences that form under cyclic climate forcing. Paired river terraces are staircases of abandoned floodplains on both valley sides, and hence preserve past valley widths. Their formation requires alternating phases of predominantly river incision and predominantly lateral planation, plus progressive valley narrowing. While cyclic Quaternary climate changes can explain shifts between incision and lateral erosion, the driving mechanism of valley narrowing is unknown. Here, we extract valley geometries from climatically formed, alluvial river-terrace sequences and show that across our dataset, the total cumulative terrace height (here: total valley height) explains 90\%-99\% of the variance in valley width at the terrace sites. This finding suggests that valley height, or a parameter that scales linearly with valley height, controls valley width in addition to river discharge and lithology. To explain this valley-width-height relationship, we reformulate existing valley-width models and suggest that, when adjusting to new boundary conditions, alluvial valleys evolve to a width at which sediment removal from valley walls matches lateral sediment supply from hillslope erosion. Such a hillslope-channel coupling is not captured in current valley-evolution models. Our model can explain the existence of paired terrace sequences under cyclic climate forcing and relates valley width to measurable field parameters. Therefore, it facilitates the reconstruction of past climatic and tectonic conditions from valley topography.},
  language  = {en}
}