Fluvial Sediment Flux Research Articles

Characterization of sediment organic matter in the outer Yangtze River Estuary using stable isotopes, optical techniques, and FT-ICR-MS: Implications for the carbon burial mechanism

The burial of sediment organic matter (SOM) in the estuary and shelf plays an important role in the global carbon cycle. However, it is challenging to determine the source, composition, and burial of SOM in the coastal sea, especially at the molecular level. This was explored in the coastal area outside the largest Yangtze River of China with multiple techniques including elemental and stable isotopic analysis, absorption spectroscopy, fluorescence excitation-emission matrices coupled with parallel factor analysis (EEMs-PARAFAC), and ultra-high resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). The end-member mixing analysis based on δ13C and δ15N showed a dominance of marine contribution (up to 70%) at most stations while the terrestrial contribution increased to >55% nearshore in summer at a high fluvial sediment flux. This was consistent with the offshore decreasing humic-like C1 and C2, humification index (HIX), %lignin-like compounds, and %CHO but increasing tryptophan-like C3, biological index (BIX), %protein-like compounds, and %CHOS from EEMs-PARAFAC and FT-ICR-MS analysis. The %clay correlated positively with SOM content, HIX, %lignin-like compounds, O/C, and modified aromaticity index (AImod) but correlated negatively with %C3, H/C, and the relative abundance of labile formulas (MLBL), while %silt showed contrasting correlations. These results indicated the fine clay sediments adsorbed more humified, aromatic, oxygenated, and terrestrial compounds that were probably more resistant to biodegradation and thus had a higher burial efficiency than those on the silty sediments. Principal component analysis based on SOM indices further revealed different characteristics of SOM in the nearshore, northern offshore, and southern offshore regions, which were probably dependent on the delivery by local current systems. Overall, these findings contributed to unraveling the source and molecular composition of SOM associated with different grain size sediments and local current delivery, which are fundamental for understanding the factors underlying carbon burial in the complex coastal environment.

Impacts of climate change and freeze–thaw cycles on water and sediment fluxes in the headwater region of the Yangtze River, Qinghai–Tibet Plateau

Variations in the suspended sediment on the Qinghai–Tibet Plateau have important implications for aquatic ecosystems. Although changes in the cryosphere induced by climate change have been shown to increase sediment yields, their impacts on water and sediment dynamics in headwater regions remain poorly investigated. Here, we examined the responses of runoff and suspended sediment dynamics to changes in the climate and ground freeze–thaw cycle in the source region of the Yangtze River (SRYR) from 1964 to 2019. Long–term daily in situ water and sediment observations provided evidence that climate change controlled change in seasonal and annual water–sediment dynamics by regulating air temperature and precipitation. Attribution analysis showed that precipitation (∼41.93 %, through driving rainfall splash, overland flow erosion, and mass wasting) and land surface temperature (∼30.66 %, through driving freeze–thaw erosion) were the major factors contributing to increasing fluvial sediment fluxes over the past 30 years. We found that freeze–thaw cycles changed the soil erosion patterns by governing the thermal state of the near–surface active layer and driving associated thermal processes. Furthermore, the extension of the thawing duration and the advance of the thawing starting date (at an average rate of 13.5 days/10 yr) exacerbated freeze–thaw erosion, leading to elevated sediment fluxes in the initial thaw and initial freezing periods. This study highlights the need to focus on cryosphere–hydrology observations in terms of sediment dynamics; these findings are critical for soil and ecological protection in alpine headwater regions.

Longitudinal scour-bar pattern in large convergent estuaries on low-lying coastal plains

A seaward decrease–increase–decrease trend in the longitudinal bed level, defined as scour-bar pattern, is observed in several large estuaries on low-lying coastal plains such as the Amazon, Yangtze and Fly. Why this pattern forms has not yet been well explained. The mechanism for the formation of this pattern is explored here using a one-dimensional morphodynamic model, with varied geometry, fluvial water discharge, sediment flux and tide. Results show that for those estuaries with bed slopes in the order of 10−5 and sediment concentration in the order of 0.1 kg m−3, bars are likely to occur for channels with relatively weak convergence and wide mouth, while scours are nearly ubiquitous. Scours are classified as fluvial and tidal based on the relative strength of river and tide, which can be distinguished by bed slope and water depth. A balance between river and tide can lead to no scours or bars. Sediment reduction and sea level rise enhances the relative strength of tide, and transition of a fluvial scour to a tidal scour may occur.

The Influence of Transport Stage on Preserved Fluvial Cross Strata

AbstractFluvial cross strata are depositional products of bedform migration that record formative flow and sediment transport conditions on planetary bodies. Bedform evolution varies with transport stage even under constant flow depths, but our understanding of how prevailing sediment transport conditions affect preserved cross strata is limited. Here, we analyzed experimental bedform evolution and preserved set thickness spanning threshold‐of‐motion to suspension‐dominated transport conditions at multiple equilibrium flow depths. Results show that bedform trough depth and mean preserved set thickness have a parabolic dependence on transport stage, with maximum values observed at intermediate transport stages. Our results indicate that transport stage is a key control on the flow‐depth‐normalized set thickness but set thickness is a poor indicator of flow depth. Thus, the dependence of bedform dimensions on transport stage should be considered in paleohydraulic reconstruction, and the analysis of set thickness may aid in the estimation of ancient fluvial sediment flux.

Global rates and patterns of channel migration in river deltas

River deltas are dynamic systems whose channels can widen, narrow, migrate, avulse, and bifurcate to form new channel networks through time. With hundreds of millions of people living on these globally ubiquitous systems, it is critically important to understand and predict how delta channel networks will evolve over time. Although much work has been done to understand drivers of channel migration on the individual channel scale, a global-scale analysis of the current state of delta morphological change has not been attempted. In this study, we present a methodology for the automatic extraction of channel migration vectors from remotely sensed imagery by combining deep learning and principles from particle image velocimetry (PIV). This methodology is implemented on 48 river delta systems to create a global dataset of decadal-scale delta channel migration. By comparing delta channel migration distributions with a variety of known external forcings, we find that global patterns of channel migration can largely be reconciled with the level of fluvial forcing acting on the delta, sediment flux magnitude, and frequency of flood events. An understanding of modern rates and patterns of channel migration in river deltas is critical for successfully predicting future changes to delta systems and for informing decision makers striving for deltaic resilience.

Exceptional increases in fluvial sediment fluxes in a warmer and wetter High Mountain Asia.

Rivers originating in High Mountain Asia are crucial lifelines for one-third of the world’s population. These fragile headwaters are now experiencing amplified climate change, glacier melt, and permafrost thaw. Observational data from 28 headwater basins demonstrate substantial increases in both annual runoff and annual sediment fluxes across the past six decades. The increases are accelerating from the mid-1990s in response to a warmer and wetter climate. The total sediment flux from High Mountain Asia is projected to more than double by 2050 under an extreme climate change scenario. These findings have far-reaching implications for the region’s hydropower, food, and environmental security.

Sediment Coarsening in Tidal Flats and Stable Coastline of the Abandoned Southern Yellow River Sub-Delta in Response to Fluvial Sediment Flux Decrease During the Past Decades

Due to remarkable reduction of sediment supply, the vulnerability of Yellow River deltaic system increased and ecological impacts occurred to some extent. To have a comprehensive and quantitative understanding of the morphological evolution of deltas, surficial sediments of tidal flat along the abandoned southern Yellow River sub-delta and two adjacent coastal units were systematically collected and evaluated by grain-size analysis in the study. The results reveal that surficial sediments of the abandoned southern Yellow River sub-delta have been coarsening significantly since the 1980s, as characterized by a decrease in both the mud content and the clay/mud ratio. In particular, the transition from cohesive to non-cohesive sediment was completed between 2007 and 2013. With a sharp decrease in sediment flux from the Yellow River estuary, the flood currents from the submarine coastal slope carry few fine particles into the tidal zone, whereas the ebb currents with reverse direction remove some fine particles from the tidal flat. This is a major cause of sediment coarsening in the tidal flat. As sediment coarsening, the coastline of the abandoned southern Yellow River sub-delta has remained stable. The significant change in the grain size of the tidal flat surficial sediments may have a profound impact on the future coastal geomorphic evolution.

Evidence for enhanced fluvial channel mobility and fine sediment export due to precipitation seasonality during the Paleocene-Eocene thermal maximum

Abstract The Paleocene-Eocene thermal maximum (PETM) was the most extreme example of an abrupt global warming event in the Cenozoic, and it is widely discussed as a past analog for contemporary climate change. Anomalous accumulation of terrigenous mud in marginal shelf environments and concentration of sand in terrestrial deposits during the PETM have both been inferred to represent an increase in fluvial sediment flux. A corresponding increase in water discharge or river slope would have been required to transport this additional sediment. However, in many locations, evidence for changes in fluvial slope is weak, and geochemical proxies and climate models indicate that while runoff variability may have increased, mean annual precipitation was unaffected or potentially decreased. Here, we explored whether changes in river morphodynamics under variable-discharge conditions could have contributed to increased fluvial sand concentration during the PETM. Using field observations, we reconstructed channel paleohydraulics, mobility, and avulsion behavior for the Wasatch Formation (Piceance Basin, Colorado, USA). Our data provide no evidence for changes in fluvial slope during the PETM, and thus no evidence for enhanced sediment discharge. However, our data do show evidence of increased fluvial bar reworking and advection of sediment to floodplains during channel avulsion, consistent with experimental studies of alluvial systems subjected to variable discharge. High discharge variability increases channel mobility and floodplain reworking, which retains coarse sediment while remobilizing and exporting fine sediment through the alluvial system. This mechanism can explain anomalous fine sediment accumulation on continental shelves without invoking sustained increases in fluvial sediment and water discharge.

Changes in sediment, nutrients and major ions in the world largest reservoir: Effects of damming and reservoir operation

River damming and reservoir operation alter hydrological process, raising concerns over far-reaching influence on fluvial water, biogeochemistry and sediment fluxes due to the common occurrence of fragmented river landscapes around the world. Here, we investigated carbon, nutrients, and geochemical conditions in the world's largest reservoir, the Three Gorge Reservoir (TGR) in China, under three different dam operations. We also analyzed long-term trends of sediment and geochemistry in response to the reservoir building and operation. We found a drastically reduced average sediment load of 32 ± 29 Mt/y during the post -TGR, which accounts for only 6.4% of the average annual sediment load (501 Mt/y) during the period, of 1950–2000. Cumulatively, over 2004–2018, sediment inflow to the TGR totaled 2090 Mt and sediment outflow (i.e. downstream of the TGR) was 480 Mt, resulting in a total of 1610 Mt (or 77%) sediment trapped in the Reservoir, equivalent to 107 Mt/y. The reservoir water is geochemically dominated by Ca2+ and HCO3− with low-moderate mineralization and excess nutrients. Concentrations of carbon, nutrients and major ions differ notably in response to reservoir operations with the highest nitrogen level under the sluicing period (SP). Major cations concentrations are low in the low water level period (LWLP), while major cations and Cl− and SO42− concentrations reach high in the SP. Concentrations of Cl−, SO42−, and Na++K+ increase 2-3-fold, increasing their relative abundance by a factor of 1.5–2. Nutrients show overall increases with considerable alteration of dominance for dissolved and particular species due to damming and anthropogenic inputs. Furthermore, dissolved inorganic nitrogen increases 8-fold during the last 50 years. The findings imply great effects of river damming and reservoir regulation on sediment transport, nutrient levels and major ion chemistry.

Air Temperature Regulates Erodible Landscape, Water, and Sediment Fluxes in the Permafrost‐Dominated Catchment on the Tibetan Plateau

AbstractApproximately 40% of the Tibetan Plateau (TP) is underlain by continuous permafrost, yet its impact on fluvial water and sediment dynamics remains poorly investigated. Here we show that water and sediment dynamics in the permafrost‐dominated Tuotuohe basin on the TP are driven by air temperature and permafrost thaw, based on 33‐year daily in situ observations (1985–2017). Air temperature regulates the seasonal patterns of discharge and suspended sediment concentration (SSC) by controlling the changes in active contributing drainage area (ACDA, the unfrozen erodible landscape that contributes hydrogeomorphic processes within a catchment) and governing multiple thermal processes such as glacier‐snow melt and permafrost thaw. Rainstorms determine the short‐lived fluvial extreme events by intensifying slope processes and channel erosion and likely also by enhancing thaw slumps. Furthermore, the SSCs at equal levels of discharges are lower in autumn (September–October) than in spring (May–June) and summer (July–August). This reduced sediment availability in autumn can possibly be attributed to the increased supra‐permafrost groundwater runoff and the reduced surface runoff and erosion. Due to rapid climate warming, the ACDA has increased significantly from 1985 to 2017, implying expanding erodible landscapes for hydrogeomorphic processes. As a result, the fluvial water and sediment fluxes have substantially increased. In a warmer and wetter future for the TP, the fluvial sediment fluxes of similar permafrost‐underlain basins will continue to increase with expanding erodible landscapes and intensifying thermal and pluvial‐driven geomorphic processes. Thus, permafrost thaw should be considered as an important driver of past and future water and sediment changes for the TP.

SO SÁNH MỘT SỐ ĐẶC ĐIỂM ĐỘNG LỰC VÀ TRẦM TÍCH VEN BỜ CHÂU THỔ SÔNG HỒNG VÀ DƯƠNG TỬ

The Red river delta coastal area (Vietnam) and Yangtze river delta coastal area (China) not only play an important role in developmental process of each country but also show typical characteristics of hydrodynamics and sediment dynamics of estuaries and delta coastal areas. Based on previous studied results of hydro-sediment dynamics in two delta coastal zones that were published, this paper gives a comparison of hydrodynamics and sediment dynamics of the coastal zones of Red river and Yangtze river. The results showed that there are some similar features of these two regions such as riverine hydrology, decreased fluvial sediment flux due to the dam, grain size of suspended sediment, alongshore sediment and morphological change. Besides, these two regions also have some distinct characteristics such as tidal regime and residual field currents.

A retrospective analysis on changes in sediment flux in the Mississippi River system: trends, driving forces, and implications

PURPOSE: The Mississippi River is the largest river in the USA and one of the most regulated rivers in the world. Understanding fluvial sediment flux changes in the Mississippi River system has critical implications for future sustainable development and management strategies. MATERIALS AND METHODS: We obtained annual runoff and suspended sediment series from the United States Geological Survey (USGS) Data Series. Here, we investigated temporal trends and historical phases of fluvial sediment flux, while also quantifying the driving forces of changes in sediment loads in the Mississippi River system using a sediment identity approach and the sediment survey records. RESULTS AND DISCUSSION: Since the earliest estimates (initially 400–500 Mt year⁻¹), land-ocean sediment reduction in the Mississippi River system has displayed two temporal phases, decreasing from 350 Mt year⁻¹ during 1952–1962 to 200 Mt year⁻¹ during 1963–2009. The decline in land-ocean sediment flux was the result of an increase in precipitation and water yield capacity being outweighed by a decrease in sediment concentration. It is estimated that a total of 24 Gt of sediment was trapped by dams and reservoirs from 1985 to 2015, while the amount of sediment reduction by soil conservation is estimated to be 15 Gt in the USA. We can deduce that reservoir construction was the dominant driver (~ 62%) influencing land-ocean sediment flux from the Mississippi River system during 1985–2015. During 1950s–1960s, reservoirs played an overwhelmingly primary role in reducing riverine sediments. In the Missouri River basin, the largest contributor of sediment to the lower Mississippi River, we found a dominant role (> 53%) of reservoirs on tributaries in trapping sediments. The decrease in land-ocean sediment flux has caused degradation of the Mississippi River delta. CONCLUSIONS: Human activities are the main factors influencing changes in land-ocean sediment flux. Therefore, there is an urgent need of a basin-wide strategic plan to maximize the benefits and minimize the risks in order to achieve sustainable management of the drainage basin and river delta.

Projections of declining fluvial sediment delivery to major deltas worldwide in response to climate change and anthropogenic stress

Deltas are resource rich, low-lying areas where vulnerability to flooding is exacerbated by natural and anthropogenically induced subsidence and geocentric sea-level rise, threatening the large populations often found in these settings. Delta ‘drowning’ is potentially offset by deposition of sediment on the delta surface, making the delivery of fluvial sediment to the delta a key balancing control in offsetting relative sea-level rise, provided that sediment can be dispersed across the subaerial delta. Here we analyse projected changes in fluvial sediment flux over the 21st century to 47 of the world’s major deltas under 12 environmental change scenarios. The 12 scenarios were constructed using four climate pathways (Representative Concentration Pathways 2.6, 4.5, 6.0 and 8.5), three socioeconomic pathways (Shared Socioeconomic Pathways 1, 2 and 3), and one reservoir construction timeline. A majority (33/47) of the investigated deltas are projected to experience reductions in sediment flux by the end of the century, when considering the average of the scenarios, with mean and maximum declines of 38% and 83%, respectively, between 1990–2019 and 2070–2099. These declines are driven by the effects of anthropogenic activities (changing land management practices and dam construction) overwhelming the effects of future climate change. The results frame the extent and magnitude of future sustainability of major global deltas. They highlight the consequences of direct (e.g. damming) and indirect (e.g. climate change) alteration of fluvial sediment flux dynamics and stress the need for further in-depth analysis for individual deltas to aid in developing appropriate management measures.

A Two Decadal (1993–2012) Numerical Assessment of Sediment Dynamics in the Northern Gulf of Mexico

We adapted the coupled ocean-sediment transport model to the northern Gulf of Mexico to examine sediment dynamics on seasonal-to-decadal time scales as well as its response to decreased fluvial inputs from the Mississippi-Atchafalaya River. Sediment transport on the shelf exhibited contrasting conditions in a year, with strong westward transport in spring, fall, and winter, and relatively weak eastward transport in summer. Sedimentation rate varied from almost zero on the open shelf to more than 10 cm/year near river mouths. A phase shift in river discharge was detected in 1999 and was associated with the El Niño-Southern Oscillation (ENSO) event, after which, water and sediment fluxes decreased by ~20% and ~40%, respectively. Two sensitivity tests were carried out to examine the response of sediment dynamics to high and low river discharge, respectively. With a decreased fluvial supply, sediment flux and sedimentation rate were largely reduced in areas proximal to the deltas, which might accelerate the land loss in down-coast bays and estuaries. The results of two sensitivity tests indicated the decreased river discharge would largely affect sediment balance in waters around the delta. The impact from decreased fluvial input was minimum on the sandy shoals ~100 km west of the Mississippi Delta, where deposition of fluvial sediments was highly affected by winds.

Exploring Wave and Sea‐Level Rise Effects on Delta Morphodynamics With a Coupled River‐Ocean Model

Deltas, which are often densely populated, have become more vulnerable to flooding due to increasing rates of sea‐level rise and decreasing sediment supply. These landscapes grow through the successive stacking of delta lobes, as abrupt changes in the river's course episodically alter the river mouth's location. The dynamics of these channel avulsions determine the location and size of delta lobes. We use a newly developed coupled model of river and coastal processes to explore how changing wave climates (varying wave heights and offshore approach angles) and a range of sea‐level rise rates affect avulsion processes and large‐scale delta morphology. Although the relative impacts of the fluvial sediment flux and wave influence have long been studied and more recently quantified, we find that the sign and magnitude of wave climate diffusivity both play important roles in determining not only delta morphology but also avulsion dynamics. We also find, surprisingly, that increasing sea‐level rise rates do not always accelerate avulsions. If the river channel is prograding rapidly enough, relative to the rate of sea‐level rise, then avulsion frequency will not be significantly affected by the rate of sea‐level rise. This finding highlights important differences between wave and river‐dominated deltas, as well as between prototypical deltas and experimental deltas created in the lab. The wave climate, sea‐level rise rate, and critical superelevation required to trigger an avulsion all play important roles in determining the degree of autogenic variability operating in delta systems, which has implications for both avulsion dynamics and interpretation of delta stratigraphy.

Fluvial Response to a Period of Hydrometeorological Change and Landscape Disturbance in the Canadian High Arctic

AbstractRecords of fluvial suspended sediment fluxes are sensitive indicators of hydrometeorological and permafrost change. Here we document the watershed‐scale suspended sediment flux response to a period of hydrometeorological change and landscape disturbance in two High Arctic rivers. Net in‐channel and extra‐channel sediment storage and changing hydrometeorological conditions dampen the downstream transport of increased sediment delivery from localized permafrost slope disturbances. Our results show that the impact of permafrost disturbance is likely a smaller effect than a shift toward a pluvially (rainfall) dominated hydrological regime in these environments. Suspended sediment transport is energy limited under contemporary hydrometeorological conditions, and the transition from a nival to pluvial dominated flow and sediment transfer regime will likely accelerate landscape change in the High Arctic.

Humans are the most significant global geomorphological driving force of the 21st century

The transformation of the Earth’s land surface by mineral extraction and construction is on a scale greater than natural erosive terrestrial geological processes. Mineral extraction statistics can be used as a proxy to measure the size of the total anthropogenic global sediment flux related to mineral extraction and construction. It is demonstrated that the annual direct anthropogenic contribution to the global production of sediment in 2015 was conservatively some 316 Gt (150 km3), a figure more than 24 times greater than the sediment supplied annually by the world’s major rivers to the oceans. The major long-term acceleration in anthropogenic sediment flux started just after the Second World War and anthropogenic sediment flux overtook natural fluvial sediment flux in the mid-1950s. Humans are now the major global geomorphological driving force and an important component of Earth System processes in landscape evolution. The changing magnitude of anthropogenic sediments and landforms over time are significant factors in the characterisation of the proposed new epoch of geological time – the Anthropocene.

Aeolian dust supply from the Yellow River floodplain to the Pleistocene loess deposits of the Mangshan Plateau, central China: Evidence from zircon U-Pb age spectra

The thick loess-palaeosol sequences in the Mangshan Loess Plateau (MLP; central China) along the south bank of the lower reach of the Yellow River provide high-resolution records of Quaternary climate change. In addition, substantial increases in grain-size and accumulation rate have been inferred in the upper part of the loess sequence, above palaeosol layer S2. This study investigates the sources of the long-term dust supply to the MLP and explores the mechanism behind the sudden increase in sediment delivery and coarsening of the loess deposits since S2 (∼240 ka) by using end member modelling of the loess grain-size dataset and single-grain zircon U-Pb dating. Our results indicate that the lower Yellow River floodplain, directly north of the MLP, served as a major dust supply for the plateau at least since the deposition of loess unit L9 and indirectly suggest that the integration of the Yellow River and the disappearance of the Sanmen palaeolake took place before L9 (∼900 ka). The sudden change in sedimentology of the Mangshan sequence above palaeosol unit S2 may result from an increased fluvial sediment flux being transported to the lower reaches of the Yellow River because of tectonic movements (initiated) in the Weihe Basin around 240 ka. Furthermore, sediment coarsening can be explained by the gradual southward migration of the lower Yellow River floodplain towards the MLP since the deposition of palaeosol S2. The migration is evidenced by the formation of an impressive scarp, and is likely caused by tectonic tilting of the floodplain area.

Coupling Climate Conditions, Sediment Sources and Sediment Transport in an Alpine Basin

AbstractIn a fluvial system, mountain basins control sediment export to the lowland rivers. Hence, analysis of erosion processes and sediment delivery patterns in mountain basins is a key factor for many applications such as land‐use management, hazard assessment and infrastructure design. Several studies have investigated the alterations triggered by recent climatic change on the hydrological regime, while only a few works have explored the consequences on fluvial sediment dynamics. Here, we combined and analyzed the quasi‐unique dataset of climatic conditions, landform response and sediment export produced, since 1986 in the Rio Cordon basin (5 km2, Eastern Italian Alps) to examine the sediment delivery processes occurring in the last 3 decades. The temperature, precipitation and fluvial sediment fluxes in the basin were analyzed using continuous measurement executed by a permanent monitoring station, while the evolution of sediment source areas was investigated using three sediment source inventories. The results showed that during the period 1986–1993 the sediment fluxes (339 Mg yr−1) reflected the stable trend of the climatic conditions. The period between the first and second source inventory (i.e. 1994–2006) was characterized by climatic fluctuations and by the occurrence of high magnitude floods. Nevertheless, a limited increase in the extent of sediment source areas was detected, suggesting that the increased sediment export (759 Mg yr−1) was mainly driven by in‐channel sediment supply. Notwithstanding the marked climate warming and the increased precipitation, a weak source area evolution and a reduction in sediment export (237 Mg yr−1) were observed during the period 2007–2015. In particular, the higher rainfall did not result in an intensification of flood events, stressing the absence of hillslope‐channel connectivity. Copyright © 2017 John Wiley & Sons, Ltd.

Perturbation of fluvial sediment fluxes following the 2008 Wenchuan earthquake

AbstractQuantifying the removal of co‐seismic landslide material after a large‐magnitude earthquake is central to our understanding of geomorphic recovery from seismic events and the topographic evolution of tectonically active mountain ranges. In order to gain more insight into the fluvial erosion response to co‐seismic landslides, we focus on the sediment fluxes of rivers flowing through the rupture zone of the 2008 Mw 7.9 Wenchuan earthquake in the Longmen Shan of the eastern Tibetan Plateau. Over the post‐seismic period of 2008–2013, we annually collected river sediment samples (0.25–1 mm) at 19 locations and measured the concentration of cosmogenic 10Be in quartz. When compared with published pre‐earthquake data, the 10Be concentrations declined dramatically after the earthquake at all sampling sites, but with significant spatial differences in the amplitude of this decrease, and were starting to increase toward pre‐earthquake level in several basins over the 5‐year survey. Our analysis shows that the amplitude of 10Be decrease is controlled by the amount of landslides directly connected to the river network. Calculations based on 10Be mixing budgets indicate that the sediment flux of the 0.25–1 mm size fraction increased up to sixfold following the Wenchuan earthquake. Our results also suggest that fluvial erosion became supply limited shortly after the earthquake, and predict that it could take a few years to several decades for fluvial sediment fluxes to go back to pre‐earthquake characteristics, depending on catchment properties. We also estimate that it will take at least decades and possibly up to thousands of years to remove the co‐seismic landslide materials from the catchments in the Longmen Shan. Copyright © 2017 John Wiley & Sons, Ltd.