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Progress in better understanding and modeling Earth surface systems requires an ongoing integration of data and numerical models. Advances are currently hampered by technical barriers that inhibit finding, accessing, and executing modeling software with related datasets. We propose a design framework for Data Components, which are software packages that provide access to particular research datasets or types of data. Because they use a standard interface based on the Basic Model Interface (BMI), Data Components can function as plug-and-play components within modeling frameworks to facilitate seamless data–model integration. To illustrate the design and potential applications of Data Components and their advantages, we present several case studies in Earth surface processes analysis and modeling. The results demonstrate that the Data Component design provides a consistent and efficient way to access heterogeneous datasets from multiple sources and to seamlessly integrate them with various models. This design supports the creation of open data–model integration workflows that can be discovered, accessed, and reproduced through online data sharing platforms, which promotes data reuse and improves research transparency and reproducibility. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive river discharge analysis to estimate past and future hydrological extremes across Morocco. Hydrological simulations with historical forcing and climate change scenario inputs have been performed to better understand the change in magnitude and frequency of extreme discharge events that cause flooding. Simulations are applied to all major rivers of Morocco, including a total of 16 basins that cover the majority of the country. An ensemble of temperature and precipitation input parameter sets was generated to analyze input uncertainty, an approach that can be extended to other regions of the world, including data-sparse regions. Parameter uncertainty was also included in the analyses. Historical simulations comprise the period 1979–2021, while future simulations (2015–2100) were performed under the Shared Socioeconomic Pathway (SSP) 2–4.5 and SSP5–8.5. Clear patterns of changing flood extremes are projected; these changes are significant when considered as a proportion of the land area of the country. Two types of basins have been identified, based on their different behavior in climate change scenarios. In the Northern/Mediterranean basins we observe a decrease in the frequency and intensity of events by 2050 under both SSPs, whereas for the remaining catchments higher and more frequent high-flow events in the form of flash floods are detected. Our analysis revealed that this is a consequence of the reduction in rainfall accumulation and intensity in both SSPs for the first type of basins, while the opposite applies to the other type. More generally, we propose a methodology that does not rely on observed time series of discharge, so especially for regions where those do not exist or are not available, and that can be applied to undertake future flood projections in the most data-scarce regions. This method allows future hydrological hazards to be estimated for essentially any region of the world. [ABSTRACT FROM AUTHOR]

Here we provide global estimates of the seasonal flux of sediment, on a river-by-river basis, under modern and prehuman conditions. Humans have simultaneously increased the sediment transport by global rivers through soil erosion (by 2.3 ± 0.6 billion metric tons per year), yet reduced the flux of sediment reaching the world's coasts (by 1.4 ± 0.3 billion metric tons per year) because of retention within reservoirs. Over 100 billion metric tons of sediment and 1 to 3 billion metric tons of carbon are now sequestered in reservoirs constructed largely within the past 50 years. African and Asian rivers carry a greatly reduced sediment toad; Indonesian rivers deliver much more sediment to coastal areas., Coastal retreat has major implications for human habitat, because >37% (2.1 billion people in 1994) of the world's population live within 100 km of a coastline, and approximately 44% live [...]

Computational modeling occupies a unique niche in Earth and environmental sciences. Models serve not just as scientific technology and infrastructure but also as digital containers of the scientific community's understanding of the natural world. As this understanding improves, so too must the associated software. This dual nature – models as both infrastructure and hypotheses – means that modeling software must be designed to evolve continually as geoscientific knowledge itself evolves. Here we describe design principles, protocols, and tools developed by the Community Surface Dynamics Modeling System (CSDMS) to promote a flexible, interoperable, and ever-improving research software ecosystem. These include a community repository for model sharing and metadata, interface and ontology standards for model interoperability, language-bridging tools, a modular programming library for model construction, modular software components for data access, and a Python-based execution and model-coupling framework. Methods of community support and engagement that help create a community-centered software ecosystem are also discussed. [ABSTRACT FROM AUTHOR]

Each year throughout the contiguous United States (CONUS), flood hazards cause damage amounting to billions of dollars in homeowner insurance claims. As climate change threatens to raise the frequency and severity of flooding in vulnerable areas, the ability to predict the number of property insurance claims resulting from flood events becomes increasingly important to flood resilience. Based on random forest, we develop a flood property Insurance Claims model (iClaim) by fusing records from the National Flood Insurance Program (NFIP), including building locations, topography, basin morphometry, and land cover, with data from multiple sources of hydrometeorological variables, including flood extent, precipitation, and operational river-stage and oceanic water-level measurements. The model utilizes two steps—damage level classification and claim number regression—and subsampling strategies designed accordingly to reduce overfitting and underfitting caused by the flood claim samples, which are unevenly distributed and widely ranged. We evaluate the model using 446,446 grid samples identified from 589 flood events occurring from 2016 to 2019 over CONUS, overlapping 258,159 claims out of a total of 287,439 NFIP records of the same period. Our rigorous validation yields acceptable performance at the grid/event, county/event, and event accumulative level, with R2 over 0.5, 0.9, and 0.95, respectively. We conclude that the iClaim model can be used in many application scenarios, including assessing flood impact and improving flood resilience. [ABSTRACT FROM AUTHOR]

Geographic simulation models can be used to explore and better understand the geographical environment. Recent advances in geographic and socio-environmental research have led to a dramatic increase in the number of models used for this purpose. Some model repositories provide opportunities for users to explore and apply models, but few provide a general evaluation method for assessing the applicability and recognition of models. In this study, an academic impact evaluation method for models is proposed. Five indices are designed based on their pertinence. The analytical hierarchy process is used to calculate the index weights, and the academic impacts of models are quantified with the weighted sum method. The time range is controlled to evaluate the life-term and annual academic impacts of the models. Some models that met the evaluation criteria from different domains are then evaluated. The results show that the academic impact of a model can be quantified with the proposed method, and the major research areas that models impact are identified. [ABSTRACT FROM AUTHOR]

Accelerated glacier‐snow‐permafrost erosion due to global warming amplifies the sediment availability in cold environments and affects the time‐varying suspended sediment concentration (SSC) and discharge (Q) relationship. Here, the sediment‐availability‐transport (SAT) model is proposed to simulate dynamic SSC‐Q relationships by integrating the sediment availability coupled by thermal processes, fluvial processes and long‐term storage exhaustion into a sediment rating curve (SSC = a × Qb with a and b as fitting parameters). In the SAT‐model, increased sediment sources from glacier‐snow‐permafrost erosion are captured by changes in basin temperature, showing an exponential amplification of SSC when basin temperature increases. Enhanced fluvial erosion by the elevated water supply from rainfall and meltwater is captured by the factor of runoff surge, which results in a linear amplification of SSC. The SAT‐model is validated for the permafrost‐dominated Tuotuohe basin on Tibetan Plateau utilizing multi‐decadal daily SSC/Q in‐situ observations (1985–2017). Results show that sediment rating curves for Tuotuohe display significant inter‐annual variations. The higher parameter‐b in a warmer and wetter climate confirms the increased sediment availability due to the expanded erodible landscapes and gullying‐enhanced connectivity between channels and slopes. Through capturing such time‐varying sediment availability, the SAT‐model can robustly reproduce the long‐term evolution, seasonality, and various event‐scale hysteresis of SSC, including clockwise, counter‐clockwise, figure‐eight, counter‐figure‐eight, and more complex hysteresis loops. Overall, the SAT‐model can explain over 75% of long‐term SSC variance with stable performance under hydroclimate abrupt changes, outperforming the conventional and static sediment rating curve approach by 20%. The SAT‐model not only advances understanding of sediment transport mechanisms by integrating thermal‐ and fluvial‐erosion processes, but also provides a model framework to simulate and project future sediment loads in other cold basins. Key Points: Glacier‐snow‐permafrost melting elevates sediment availability by enlarging erodible landscapes and enhancing channel‐slope connectivityA sediment‐availability‐transport (SAT)‐model is developed to simulate dynamic suspended sediment concentration (SSC)‐discharge relations by integrating sediment availability controlled by thermal/fluvial processesThe SAT‐model can robustly reproduce the long‐term evolution, seasonality and various event‐scale hysteresis of SSC for cold basins [ABSTRACT FROM AUTHOR]

Approximately 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. Key Points: Climate warming expands the erodible landscape and increases fluvial water and sediment fluxes on the Tibetan PlateauAir temperature regulates seasonal discharge and sediment dynamics by controlling glacier‐snow melt and permafrost processesIncreasing rainstorms results in more frequent fluvial extreme events [ABSTRACT FROM AUTHOR]

Accurate determination of past flooding characteristics is necessary to effectively predict the future flood disaster risk and dominant controls. However, understanding the effects of environmental forcing on past flooding frequency and magnitude is difficult owing to the deficiency of observations (data available for less than 10 % of the world's rivers) and extremely short measurement time series (<100 years). In this study, a numerical model, HYDROTREND, which generates synthetic time series of daily water discharge at a river outlet, was applied to the Yalu River to (1) reconstruct annual peak discharges over the past 1000 years and estimate flood annual exceedance probabilities and (2) identify and quantify the impacts of climate change and human activity (runoff yield induced by deforestation and dam retention) on the flooding frequency and magnitude. Climate data obtained from meteorological stations and ECHO-G climate model output, morphological characteristics (hypsometry, drainage area, river length, slope, and lapse rate), and hydrological properties (groundwater properties, canopy interception effects, cascade reservoir retention effect, and saturated hydraulic conductivity) form significant reliable model inputs. Monitored for decades, some proxies on ancient floods allow for accurate calibration and validation of numerical modeling. Simulations match well the present-day monitored data (1958–2012) and the literature records of historical flood events (1000–1958). They indicate that flood frequencies of the Yalu River increased during 1000–1940, followed by a decrease until the present day. Frequency trends were strongly modulated by climate variability, particularly by the intensity and frequency of rainfall events. The magnitudes of larger floods, events with a return period of 50 to 100 years, increased by 19.1 % and 13.9 %, respectively, due to climate variability over the last millennium. Anthropogenic processes were found to either enhance or reduce flooding, depending on the type of human activities. Deforestation increased the magnitude of larger floods (100- and 50-year floods) by 19.2 %–20.3 %, but the construction of cascade reservoirs in 1940 significantly reduced their magnitude by 36.7 % to 41.7 %. We conclude that under intensified climate change and human activities in the future, effective river engineering should be considered, particularly for small- and medium-sized mountainous river systems, which are at a higher risk of flood disasters owing to their relatively poor hydrological regulation capacity. [ABSTRACT FROM AUTHOR]

Accurate determination of past flooding characteristics is necessary to effectively predict future flood disaster risk and the dominant controls. However, understanding the role of environmental forcing on past flooding frequency and magnitude is difficult due to the deficiency of observations and too short measurement time series. Here, a numerical model HydroTrend, that generates synthetic time series of daily water discharge at a river outlet, is applied to Yalu River to: (1) reconstruct annual peak discharges over the past 1000 years and estimate flood annual exceedance probabilities; (2) identify and quantify the impacts of climate change and human activity (runoff yield induced by deforestation and dam retention) on the flooding frequency and magnitude. Climate data obtained from meteorological stations and ECHO-G climate model output, morphological characteristics (hypsometry, drainage area, River length, slope and Lapse rate) and hydrological properties (groundwater properties, canopy interception effects, cascade reservoirs retention effect and saturated hydraulic conductivity) are form the significant reliable model inputs. Monitored for decades and some proxies on ancient floods allow for accurate calibration and validation of numerical modeling. Simulations match well present-day monitored data (1958-2012) and historical flood events literature records (1000-1958). They indicate that flood frequencies of Yalu River increased during AD 1000-1940, followed by a decrease until the present day. Frequency trends were strongly modulated by climate variability, particularly by intensity and frequency of rainfall events. The magnitudes of larger floods, events with a return period of 50 to 100 years, increased by 19.1 and 13.9%, respectively, due to climate variability over the last millennium. Anthropogenic processes were found to either enhance or reduce flooding, depending on the type of the human activities. Deforestation increased the magnitude of larger floods by 19.2-20.3%, but the construction of cascade reservoirs in AD 1940 significantly reduced their magnitude by 36.7 to 41.7%. We conclude that under intensified climate change and human activity in the future, effective river engineering should be considered, particularly for small and medium-sized mountainous river systems, which are at higher risk of flood disasters due to their relatively poor capacity for hydrological regulation. [ABSTRACT FROM AUTHOR]

Remote sensing analysis is routinely used to map flooding extent either retrospectively or in near-real time. For flood emergency response, remote-sensing-based flood mapping is highly valuable as it can offer continued observational information about the flood extent over large geographical domains. Information about the floodwater depth across the inundated domain is important for damage assessment, rescue, and prioritizing of relief resource allocation, but cannot be readily estimated from remote sensing analysis. The Floodwater Depth Estimation Tool (FwDET) was developed to augment remote sensing analysis by calculating water depth based solely on an inundation map with an associated digital elevation model (DEM). The tool was shown to be accurate and was used in flood response activations by the Global Flood Partnership. Here we present a new version of the tool, FwDET v2.0, which enables water depth estimation for coastal flooding. FwDET v2.0 features a new flood boundary identification scheme which accounts for the lack of confinement of coastal flood domains at the shoreline. A new algorithm is used to calculate the local floodwater elevation for each cell, which improves the tool's runtime by a factor of 15 and alleviates inaccurate local boundary assignment across permanent water bodies. FwDET v2.0 is evaluated against physically based hydrodynamic simulations in both riverine and coastal case studies. The results show good correspondence, with an average difference of 0.18 and 0.31 m for the coastal (using a 1 m DEM) and riverine (using a 10 m DEM) case studies, respectively. A FwDET v2.0 application of using remote-sensing-derived flood maps is presented for three case studies. These case studies showcase FwDET v2.0 ability to efficiently provide a synoptic assessment of floodwater. Limitations include challenges in obtaining high-resolution DEMs and increases in uncertainty when applied for highly fragmented flood inundation domains. [ABSTRACT FROM AUTHOR]

The Surface Water and Ocean Topography (SWOT) mission will measure water surface elevations and inundation extents of rivers of the world but with limited temporal sampling. By comparing flood location and duration of 4,664 past flood events recorded by the Dartmouth Flood Observatory to SWOT's orbit ephemeris, we estimate that SWOT would have seen 55% of these, with higher probabilities associated with more extreme events and with those that displaced more than 10,000 people. However, SWOT measurements will exhibit uneven temporal sampling and may require a combination of data obtained at different times to accurately characterize large events. This is illustrated using recent flooding in the United States, in eastern Iowa and in Houston and surrounding areas from Hurricane Harvey. SWOT data have significant potential to improve flood forecasting models by offering data needed to enhance flow routing modeling, provided that users can overcome the potential hurdles associated with its temporal and spatial sampling characteristics. Plain Language Summary: The Surface Water and Ocean Topography (SWOT) satellite mission will simultaneously measure water surface elevations and inundated areas for the Earth's land surface. Such information can be valuable for improving flood models and their calibration; however, SWOT temporal sampling will be limited, with most locations in the world being seen once every 7 to 10 days, which may cause it to miss floods. Using a record of global flood information, including duration and location, compiled by the Dartmouth Flood Observatory and the expected satellite orbit, we estimated that, if already operational, SWOT would have collected at least one measurement over 55% of these events. We illustrate SWOT data coverage using flood inundation maps generated for flooding in eastern Iowa (2008) and in Houston and surrounding areas, Texas, caused by Hurricane Harvey (2017). Due to the novelty of this kind of hydrological information, particularly in the way SWOT samples rivers in time and space, early engagement of potential users may be instrumental to maximize the utility of this open source of worldwide observations of rivers, lakes, and inundated land. Key Points: SWOT temporal and spatial observation capabilities and limitations are evaluated using recent floods in eastern Iowa and from Hurricane HarveyDuring its life cycle, SWOT may observe hundreds of flood events, including over data‐scarce regionsDartmouth Flood Observatory data suggest that more destructive floods tend to last longer and are more likely to be observed by SWOT [ABSTRACT FROM AUTHOR]

The lower Yellow River channel was maintained by artificial levees between 1580 and 1849. During this period, 280 levee breaches occurred. To estimate sediment storage on the floodplains outside the levees, a regression model with a decadal time step was developed to calculate the outflow ratio for the years when levee breaching occurred. Uncertainty analysis was used to identify the likely outflow ratio. Key variables of the model include annual water discharge, a proxy for levee conditions, and potential bankfull discharge of the channel before flood season. Uncertainty analysis reveals an outflow ratio of 0.35–0.56. We estimate that during this period, 18.8–30.1% of the total ~312 Gt of sediment load was deposited on the floodplains outside the levees. Human‐accelerated erosion in the Loess Plateau caused a 4‐fold increase in sediment delivery to the lower Yellow River, which could not be accommodated by channel morphodynamic changes. As a result, 21.2–27.5% of the total sediment load was deposited within the levees, creating a super‐elevated channel bed that facilitated an uncommonly high breach outflow ratio. Hence, the factor of a large super‐elevation relative to the mean main channel depth should be considered when designing diversions to restore floodplains. © 2018 John Wiley & Sons, Ltd. Around 24% of the sediment was deposited in the channel belt and floodplains within levees, 19–30% was trapped in the floodplains outside the levees, and the rest was delivered to the delta area. Human‐accelerated erosion in the Loess Plateau caused a super‐elevated channel bed on the lower river, which favors sediment trapping in the floodplains outside the levees. [ABSTRACT FROM AUTHOR]

Abstract The Congo River is the world's second largest river in terms of drainage area and water discharge. Monitored for decades, a large dataset is available, onshore for both the hydrology and sediment load, and offshore by many paleo-environmental proxies compiled at the Late-Quaternary time-scale. These numerous data allow for accurate calibration of numerical modeling. In this study, we aim to numerically quantify the evolution of sediment supply leaving the tropical Congo watershed during the last 155 ka and to decipher the forcing parameters that control this sediment supply over glacial/interglacial stages. For this, a modified version of the model HydroTrend, that besides morphologic, climatic, hydrologic, lithologic, land cover and anthropogenic factors now also considers sediment deposition on the floodplain, is used. In addition, a method to quantify the impact of natural vegetation changes is developed. Simulations match well the present-day observed data. They indicate that a significant portion of suspended sediments is trapped on the floodplain. Long-term simulations indicate that environmental changes between glacial and interglacial stages account for a 30% maximum variation of sediment supply. Climatic changes - precipitation and temperature, account for a maximum decrease in sediment supply of 20% during cold periods while conversely, induced land cover changes (loss of forest during colder and dryer stages) lead to enhanced sediment supply up to 30%. Over a longer period, the average sediment supply remained almost constant during glacial and interglacial periods, while peaks may have occurred during a warming period, just before forests had time to recover the catchment, i.e. during post-glacial periods. These moderate changes in sediment export, despite major changes in climate and vegetation cover, can be explained by the efficiency of sediment trapping of large tropical catchments that buffer fluvial fluxes towards the ocean. [ABSTRACT FROM AUTHOR]

Floods are costly to global economies and can be exceptionally lethal. The ability to produce consistent flood hazard maps over large areas could provide a significant contribution to reducing such losses, as the lack of knowledge concerning flood risk is a major factor in the transformation of river floods into flood disasters. In order to accurately reproduce flooding in river channels and floodplains, high spatial resolution hydrodynamic models are needed. Despite being computationally expensive, recent advances have made their continental to global implementation feasible, although inputs for long-term simulations may require the use of reanalysis meteorological products especially in data-poor regions. We employ a coupled hydrologic/hydrodynamic model cascade forced by the 20CRv2 reanalysis data set and evaluate its ability to reproduce flood inundation area and volume for Australia during the 1973-2012 period. Ensemble simulations using the reanalysis data were performed to account for uncertainty in the meteorology and compared with a validated benchmark simulation. Results show that the reanalysis ensemble capture the inundated areas and volumes relatively well, with correlations for the ensemble mean of 0.82 and 0.85 for area and volume, respectively, although the meteorological ensemble spread propagates in large uncertainty of the simulated flood characteristics. [ABSTRACT FROM AUTHOR]

The distinctive plan-view shape of the Ebro Delta coast reveals a rich morphologic history. The degree to which the form and depositional history of the Ebro and other deltas represent autogenic (internal) dynamics or allogenic (external) forcing remains a prominent challenge for paleo-environmental reconstructions. Here we use simple coastal and fluvial morphodynamic models to quantify paleo-environmental changes affecting the Ebro Delta over the late Holocene. Our findings show that these models are able to broadly reproduce the Ebro Delta morphology, with simple fluvial and wave climate histories. Based on numerical model experiments and the preserved and modern shape of the Ebro Delta plain, we estimate that a phase of rapid shoreline progradation began approximately 2100 years BP, requiring approximately a doubling in coarse-grained fluvial sediment supply to the delta. River profile simulations suggest that an instantaneous and sustained increase in coarse-grained sediment supply to the delta requires a combined increase in both flood discharge and sediment supply from the drainage basin. The persistence of rapid delta progradation throughout the last 2100 years suggests an anthropogenic control on sediment supply and flood intensity. Using proxy records of the North Atlantic Oscillation, we do not find evidence that changes in wave climate aided this delta expansion. Our findings highlight how scenario-based investigations of deltaic systems using simple models can assist first-order quantitative paleo-environmental reconstructions, elucidating the effects of past human influence and climate change, and allowing a better understanding of the future of deltaic landforms. [ABSTRACT FROM AUTHOR]

Recent discharge observations are lacking for most rivers globally. Discharge can be estimated from remotely sensed floodplain and channel inundation area, but there is currently no method that can be automatically extended to many rivers. We examined whether automated monitoring is feasible by statistically relating inundation estimates from moderate to coarse (>0.05°) resolution remote sensing to monthly station discharge records. Inundation extents were derived from optical MODIS data and passive microwave sensors, and compared to monthly discharge records from over 8000 gauging stations and satellite altimetry observations for 442 reaches of large rivers. An automated statistical method selected grid cells to construct 'satellite gauging reaches' (SGRs). MODIS SGRs were generally more accurate than passive microwave SGRs, but there were complementary strengths. The rivers widely varied in size, regime, and morphology. As expected performance was low ( R < 0.7) for many (86%), often small or regulated, rivers, but 1263 successful SGRs remained. High monthly discharge variability enhanced performance: a standard deviation of 100-1000 m3 s−1 yielded ca. 50% chance of R > 0.6. The best results ( R > 0.9) were obtained for large unregulated lowland rivers, particularly in tropical and boreal regions. Relatively poor results were obtained in arid regions, where flow pulses are few and recede rapidly, and in temperate regions, where many rivers are modified and contained. Provided discharge variations produce clear changes in inundated area and gauge records are available for part of the satellite record, SGRs can retrieve monthly river discharge values back to around 1998 and up to present. [ABSTRACT FROM AUTHOR]

The Poyang Lake catchment, an important sub-catchment of Changjiang, experienced ‘Little Ice Age’ (LIA) and accelerating intensity of human activities during the last 1000 years. As such, the area and time period serve as a perfect case to study the variations in water and sediment discharge under combined natural and anthropogenic impact. Simulation results of the model HydroTrend indicate that the annual average cumulative water discharge of the five rivers entering Poyang Lake over the last 1000 years is 103.65 ± 1.80 km3, and climate change is the dominating factor determining water discharge variations over time. Influenced by the LIA (AD 1451–1850), the total water discharge of the five rivers was reduced by 10%. Sediment load discharging into Poyang Lake by the five rivers was only 9.21 ± 0.43 Mt yr−1 between AD 1000 and 1700, when the anthropogenic impact on the landscape was still low. However, with the human activities accelerating during the past 300 years, the sediment load entering Poyang Lake underwent a drastic change. Because of intensified soil loss, the total sediment load entering Poyang Lake during AD 1800–1950 increased by 58.7%, compared with AD 1000–1700. After AD 1950, the sediment load variation is mainly reflected by the combined impact of dam emplacement and soil erosion. As sediment interception by dams continuously increased over time, the total sediment load entering Poyang Lake during AD 1990–2000 is only 60.9% of that of the highest riverine sediment flux during AD 1951–1980, which is almost equal to that of the lowest level during AD 1000–1700. The sediment load of many rivers in the world exhibited similar variation trends as that of Poyang Lake under combined impact of climate change and human activities. Better understanding the mechanisms of these variation trends is helpful to analyzing the formation and evolution of an estuary-shelf sedimentary system over the Holocene. [ABSTRACT FROM AUTHOR]

Current models aiming to simulate contemporary sediment yield (SY) implicitly assume that tectonic effects are either irrelevant or are reflected by catchment topography. In this study we analyse the relation between SY and seismic activity, a component of tectonic processes. Results show a spatial correlation between SY and seismic activity expressed as the estimated peak ground acceleration (PGA) with a 10% exceedance probability in 50 years. PGA has a significant impact on the spatial variation of SY, even after correcting for cross-correlations with topography, lithology or other factors that may influence SY. Based on three distinct data sets, we demonstrate that this effect is significant both for small catchments in Europe (0.3–3940 km2) and for large river systems worldwide (1580–6.15×106 km2) and that seismic activity may be even more important for explaining regional variation in SY than land use or many other commonly considered factors (e.g. catchment area, climate). We show that explicitly considering seismic activity may lead to SY-estimates that easily deviate a factor 2 or more compared to estimates that do not consider seismic activity. This is not only the case for highly seismically active regions: also in regions with a weak to moderate seismic regime seismic activity helps explaining regional patterns in SY. We argue that these findings have important implications for a better understanding of SY and its sensitivity to human impacts, as well as for our comprehension of sediment fluxes at longer timescales. [ABSTRACT FROM PUBLISHER]

Abstract: Fluvial sediment discharge can vary in response to climate changes and human activities, which in return influences human settlements and ecosystems through coastline progradation and retreat. To understand the mechanisms controlling the variations of fluvial water and sediment discharge for the Ebro drainage basin, Spain, we apply a hydrological model HydroTrend. Comparison of model results with a 47-year observational record (AD 1953–1999) suggests that the model adequately captures annual average water discharge (simulated 408m3 s−1 versus observed 425m3 s−1) and sediment load (simulated 0.3Mtyr−1 versus observed 0.28±0.04Mtyr−1) for the Ebro basin. A long-term (4000-year) simulation, driven by paleoclimate and anthropogenic land cover change scenarios, indicates that water discharge is controlled by the changes in precipitation, which has a high annual variability but no long-term trend. Modeled suspended sediment load, however, has an increasing trend over time, which is closely related to anthropogenic land cover variations with no significant correlation to climatic changes. The simulation suggests that 4000years ago the annual sediment load to the ocean was 30.5Mtyr−1, which increased over time to 47.2Mtyr−1 (AD 1860–1960). In the second half of the 20th century, the emplacement of large dams resulted in a dramatic decrease in suspended sediment discharge, eventually reducing the flux to the ocean by more than 99% (mean value changes from 38.1Mtyr−1 to 0.3Mtyr−1). [Copyright &y& Elsevier]

Abstract: This paper focuses on the delivery of water and sediment to the northern Adriatic to better understand the short-term evolution of continental margin sedimentation under natural and human impact. For that reason, the Po and six Apennine rivers (Metauro, Musone, Potenza, Tronto, Chienti and Pescara) are investigated. The climate-driven hydrological model HydroTrend is used to simulate discharge and sediment loads where observational data are limited. The northern Apennine hinterland has a significant impact on the sediment flux leaving the Po River, contributing 56% of the sediment it delivers to the Adriatic Sea. The Po River experienced a strong decrease in its sediment load (17.2–6.4Mt/yr) across 1933–1987, in contrast to a small increase in its water discharge. The rivers draining the southern Apennine hinterland contribute more than 50% of the sediment load entering the Adriatic Sea, and this is in spite of human modification of their discharge through numerous small reservoirs that invariably reduce a river''s sediment load. As a result, hyperpycnal flows, which historically carried 20–40% of the sediment flux from these Apennine rivers, become rare. Sediment load reduction is also reflected by retreat of the Apennine coastline. Based on the ART model (used in HydroTrend), the total sediment load to the northern Adriatic is 43MT/yr where the northern Alpine rivers contribute 8MT/yr, the Po River 13MT/yr and the Apennine rivers contribute 22MT/yr. [Copyright &y& Elsevier]

A global scale approach involving data assimilation schemes (e.g. Distributed Oceanographic Data System) is designed to simulate the discharge of sediment to the coastal ocean at the dynamic level (daily). The result is either a realtime, hindcast or forecast picture of coastal hydrology optimized to estimate sediment loads of rivers. The approach links a compendium of global and regional web-based databases into a GIS system. Relational and spatial methods (i.e. RiverTools®, HYDRO1k, ArcInfo®,) facilitate the process of data acquisition useful to sediment discharge models (i.e. HydroTrend). As a climate-driven hydrological model, HydroTrend incorporates drainage basin properties (river networks, hypsometry, relief, lakes or reservoirs, distributary channels) through high-resolution digital elevation models, along with other biophysical parameters I basin-average temperature, precipitation, evapo-transpiration. canopy, soil depth, hydraulic conductivity, ice fields). The schema is designed to provide important boundary conditions for marine sediment-dispersal models, concomitant with ocean data (wind, wave, currents). Considering that <4% of world-rivers are monitored for their sediment loads, the approach provides a unique means to predict the sediment flux across an entire coastline at a high-resolution temporal scale. Model comparison to long-term (1950-1994) observations from the Lanyang River (Hsi), Taiwan is shown to capture average conditions and inter- and intra-annual variability of water discharge, sediment concentration and loads. [ABSTRACT FROM AUTHOR]