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This study examines the role of topography as a dynamic boundary condition that limits the efficiency of fluvial erosion in the post-glacial Teton Range landscape. The volume of sediment currently stored in two major catchments was estimated using high-resolution LiDAR and geometric reconstructions of depth to bedrock. Seismic reflection data in Moran Bay reveals post-glacial sediment preserved behind a submerged moraine, which isolates the bay from the larger Jackson Lake depocenter. The volume of post-glacial sediment stored in the canyons and bay totals 173.82 ± 19.5336.0 (×10−3 km3), which translates to a catchment-wide sediment production rate of 0.17 ± 0.02 mm/yr. The rock-equivalent sediment volume in Moran Bay is 4.4 ± 0.9 (×10−3 km3), only ∼2.6% of the total post-glacial volume. While the estimated sediment production rate in the canyons is similar to the uplift rate, the denudation rate derived from Moran Bay sediment is 0.004 ± 0.001 mm/yr, implying highly inefficient post-glacial sediment transport. The fluvial system has been disequilibrated by glacial erosion such that interglacial valley profiles lack the steepness needed to transport sediment, delaying sediment evacuation until the next glacial advance, or until uplift sufficiently steepens the fluvial system so that it regains efficiency. Furthermore, colluvial production rates in the deglaciated valleys are close to long-term denudation and uplift rates, suggesting that once topography has been equilibrated to glacial erosion processes, subsequent glaciers do not need to produce much bedrock erosion, but mainly sweep out accumulated sediment to maintain equilibrium. • Sediment budget quantified for two catchments in the Teton Range, Wyoming. • Flattened post-glacial topography limits efficient fluvial erosion. • Sediment transport delayed until next glacial advance or uplift steepens system. • Colluvial production rates are close to long-term denudation and uplift rates. • Subsequent glaciers may not need to produce much bedrock erosion. [ABSTRACT FROM AUTHOR]

Nowadays there are numerous computational tools to forecast the evolution of the shoreline position in sandy coast environments. However, few studies have waited for the time horizon of the predictions to actually check the accuracy of the forecasted scenarios. Thus, this work proposed to assess the accuracy of medium-term predictions made with Long-Term Configuration (LTC) and GENEralised model for SImulating Shoreline change (GENESIS) numerical models for the time horizon of 15-year and evaluate the models' performance in forecasting the actual status of a complex sandy coastal stretch in 2018, the targeting year. The projection premises were already presented in Baptista et al. (2014) on which observational data used to calibrate and blind hindcast future scenarios of shoreline development was discussed. The case study focused on an area located downdrift of Poço da Cruz groin, on the northwest Portuguese coast, and considered two beach sectors in accordance with Baptista et al. (2014): sector AC, about 3.5 km long, and sector AB, about 2.4 km long and included in the first one. The whole coastal stretch is composed of sandy beaches, and past trends highlight erosion downdrift of Poço da Cruz groin due to the interruption of sediment transport. A monitoring program performed by the University of Aveiro between 2003 and 2018 (corresponding to the period of simulation presented in Baptista et al., 2014), including six topographic surveys, was considered for comparison with the projections previously made. An additional topographic survey performed in 2018, within COSMO programme, was also considered. Simulations results have proved divergent performances of LTC and GENESIS models, despite the equity of inputs parameters and modelling processes. It is concluded that GENESIS and LTC, considering the typical (TYP) wave climate (randomly generated to represent the typical frequencies of wave height and direction during five years), create an envelope (GENESIS below and LTC above) to the real average results. For TYP, GENESIS underestimates the mean retreat rates up to 23 m in sector AB and up to 23 m in AC; LTC overestimates the retreat up to 33 m in sector AB and up to 13 m in AC. Conversely, observed (OBS) wave climate (shorter characterisation period but maintaining the registered data sequence) projections overestimate the shoreline retreat in both coastal stretches, suggesting that a larger characterisation period should be more important than maintaining the sequence of recorded waves. For OBS, the models overestimate the mean retreat rates in both sectors: GENESIS overestimates up to 90 m in sector AB and up to 51 m in AC; LTC overestimates up to 60 m in AB and up to 60 m in AC. Also, the consideration of the artificial nourishment operations executed during the simulation period leads to better results in the LTC, which was overestimating the erosion rate. This showed that if all man-made interventions could be anticipated, the average retreat in the main sector, AC, would only be up to 5 % different from the projections made by Baptista et al. (2014) with LTC model and TYP wave climate. • Checked accuracy of 15-year forecasts. • Checked performance of LTC and GENESIS shoreline evolution models. • The wave sampling period used in calibration has relevant impact on forecasts made. • LTC and GENESIS create an envelope to the real average retreat surveyed. • Better projections would be achieved if planed interventions were known in advance. [ABSTRACT FROM AUTHOR]

Approximately 200,000 landslides were triggered by the 2008 Wenchuan earthquake and subsequent strong rainfall events, and the amount of landslide sediment delivered to the channels within catchments depended on the amount of landslide debris generated by the earthquake and the amount of post-earthquake rainfall. To better understand long-term hillslope erosion and the long-term changes in landslide–channel coupling, this study quantifies the coupling degree of landslide–channel by defining a landslide-channel coupling index (LCCI) and estimates the long-term hillslope erosion driven by landslides within 12 debris flow basins. We track landslide activity using multiyear imagery from 2008 to 2019, and the landslide ratio, landslide new regeneration ratio, and landslide reactivated ratio indicate that the overall landslide activity decayed following the Wenchuan earthquake. The calculation results of the coupling index illustrate that the coupling degree of landslide–channel in the study area follows a power law trend of decay over time. However, due to the influence of landslide activity, the coupling index decreased significantly in the first 5 years after the Wenchuan earthquake and then decreased slowly. The hillslope erosion driven by landslides is estimated using a conservative statistical model. The result shows that the landslide-driven hillslope erosion has decayed following a power law, and elevated levels of erosion may last for an unexpectedly long period. In addition, the landslide–channel coupling degree affects the movement of landslide sediment to channels. While the coupling degree of landslide–channel and the amount of landslide sediment supplied to the channels have decreased significantly in recent years, abundant landslide sediment could still be delivered to the channels when strong rainfall occurs in this region. Furthermore, a considerable amount of sediment appears to remain within the tributary channels and trunk channels, which means the activity of debris flow may last longer period than hillslope erosion. • A new method was developed to quantify the degree of landslide-channel coupling. • First decadal time series analysis of sediment transport is carried after the Wenchuan earthquake. • Hillslope erosion driven by landslide decayed over time following a power law. • The coupling degree of landslide-channel affects the downslope movement of landslide sediment. [ABSTRACT FROM AUTHOR]

• Under the action of concentrated flow, the change of surface runoff of karst gently sloping farmland is mainly controlled by the magnitude of concentrated flow. • Under the action of concentrated flow, the underground runoff of karst gentle slope farmland is significantly negatively correlated with the slope. • Concentrated flow can lead to severe soil erosion in karst gently sloping farmland. Exposed bedrock in karst areas considerably alters runoff paths causing partial runoff to converge into a concentrated flow, which is a potential source of soil erosion risk. However, research is lacking on how concentrated flow affects regional soil erosion. In this study, the surface and underground dual structure in karst areas was simulated in a steel tank. Combined with runoff plot monitoring, the runoff conversion process and erosion characteristics of gently sloping farmland in karst areas under different water discharge rates were examined through indoor concentrated flow discharge scouring tests, and the influence of concentrated flow changes on the runoff spatial distribution and sediment yield in gently sloping farmland was clarified. The results demonstrated the following: (i) there existed a significant positive correlation between surface runoff and the water discharge rate (p < 0.01); the partial correlation coefficient value reached 0.87. The higher the water discharge rate, the more surface runoff formation was facilitated. (ii) When the slope remained the same, the underground runoff was relatively high at 3 L/min. Given the same discharge, a significant negative correlation between underground runoff and slope was found (p < 0.05); the partial correlation coefficient value reached −0.71. (iii) In response to a water discharge rate of 5 L/min, surface soil erosion was serious, and the maximum sediment transport modulus was 174.088 g/min∙m2. A significant cubic function relationship existed between the scouring time and surface sediment yield. Overall, a critical flow rate occurred between 3 and 5 L/min, which controlled changes in surface runoff, subsurface runoff and surface sediment yield. Under highly concentrated flow, drastic soil erosion could occur. These results can provide a scientific basis for the control and prevention of concentrated flow-induced erosion in karst areas. [ABSTRACT FROM AUTHOR]

The long-distance transport of Yellow River sediments has formed an omega-shaped ('Ω') distal muddy deposit in the Yellow Sea. Numerous studies have investigated the sediment dynamics and sedimentary evolution of the deposit, but several key questions remain unanswered due to insufficient observations. To reveal the mechanisms of sediment dynamics and quantify sediment transport and deposition processes, this study collected field datasets in the depocenter of the muddy deposit off the Shandong Peninsula. Bottom mounted tripods were deployed from August 18 to 27, 2017, and from February 23 to March 2, 2018, during which two strong wind events with speeds of over 10.8 m/s occurred. The results showed that near-bed suspended sediment concentration responded directly to varying hydrodynamic conditions, and significant differences in suspended sediment concentration between two wind events could be ascribed to a number of factors (e.g., tidal current, wave periods, wind stress, turbulence). The harmonic analysis demonstrated that suspended sediment variations during the spring tide were directed mainly by resuspension, while resuspension and advection contributed equally at neap tide. The variations in background suspended sediment concentration can be ascribed to the residual current. Furthermore, the sediment transport pattern is similar to the pattern of water circulation. Generally, the along-shore suspended sediment flux is about one order of magnitude higher than the cross-shore flux. In summer, the suspended sediment was transported mainly downcoast. In winter, sediment was transported downcoast during wavy periods and upcoast during calm periods. Advection dominated sediment flux in most cases, except during wavy periods when local resuspension increased significantly, and the contribution of resuspension term to along-shore flux was up to 87%. Meanwhile, cross-shore flux also increased significantly under strong winds, which was simultaneously modulated by downcoast and offshore winds. After statistical analysis, we found that offshore winds controlled the cross-shore sediment transport in winter. Using parameterized calculation and statistical analysis, the average accumulation rate of the study site was estimated to be 0.6 cm/yr. During calm periods, lower background sediment concentration in summer led to lower deposition rates than in winter. In addition, the frequent strong wind events in winter cause extremely high erosion rates. This study provides new perspectives on quantitative variations in suspended sediment transport and regional erosion/deposition from synoptic to seasonal variations in the distal mud deposit. • In-situ observations at the bottom boundary layer were conducted in summer and winter on the muddy deposit off the Shandong Peninsula. • The advection dominates sediment flux in most cases, except for during wind gusts when local resuspension increases significantly. • Combining parameterized method and observational data, the accumulation rate is estimated. [ABSTRACT FROM AUTHOR]

• Both temporal and spatial declines existed in the channel erosion efficiency of the Lower Yellow River. • An excessive decrease in sediment transport capacity and a deficit of riverbed supply led to the temporal decline in channel erosion efficiency. • Cross-sectional geometry and bed material composition were the key factors to cause the differences in channel erosion efficiency of different reaches in the LYR. The operation of the Xiaolangdi Reservoir has exerted prominent effects on the processes of sediment transport and channel evolution in the Lower Yellow River (LYR) since 2000. The investigation into the spatio-temporal adjustment characteristics of channel evolution is of significance to the management of the LYR covering different channel-pattern reaches of braided, transitional and meandering. An indicator of channel erosion efficiency was firstly defined as the ratio of annual channel evolution volume to annual incoming water volume in a specified study reach. Furthermore, the values of channel erosion efficiency in different reaches of the LYR were calculated using the measured hydrological data and cross-sectional profiles during the post-dam stage. Calculated results show that the channel erosion efficiency in the LYR was exhibiting a decline tendency at both temporal and spatial scales, with the mean value of the whole reach decreasing from 6.0 (2000–2007) to 2.7 (2008–2020) and that of the braided reach four times higher than the meandering reach. Main factors influencing the channel erosion efficiency were investigated, covering the incoming flow-sediment regime, riverbed composition and cross-sectional geometry. The temporal decreases in these factors, including incoming sediment coefficient, bed material supply and geomorphic coefficient, resulted in the temporal decline in channel erosion efficiency. The discrepancies in channel erosion efficiency of different reaches were mainly ascribable to the variations in cross-sectional geometry and riverbed composition. The geomorphic coefficient in the braided reach decreased from 19.7 to 9.0 m−1/2, and meanwhile the percentages of fine and medium grain sizes in the riverbed reduced by around 50% from 2000 to 2020, which led to the most dramatic variation in channel erosion efficiency and the different trajectory of channel evolution. In addition, the seldom varied channel slope played a minor role in the temporal variation of channel erosion efficiency, but partly accounted for the spatial reduction along the LYR. This study provides an illustrative example for the response of a large alluvial river with different channel patterns to the varying boundary conditions caused by upstream damming. [ABSTRACT FROM AUTHOR]

• Rill erosions impacted by saturation & subsurface water flow are compared. • Method is suggested to quantify rill erosion affected by subsurface water flow. • A method is evaluated to determine rill erosion function with few data points. • Rill erosion models are applicable to slopes with subsurface water flow. Understanding rill erosion processes on purple soil slopes with subsurface water flow at different depths is of great significance to determine rill erosion model parameters. The purposes of this study were to quantify the influences of subsurface water flow at different depths on the rill erosion process. Laboratory experiments were carried out to measure sediment delivery under 5°, 10°, 15°, and 20° slope gradients, 2, 4, and 8 L min−1 flow rates and 0, 5, 10, and 15 cm subsurface water flow depths (SWFDs) below the soil surface at eight slope lengths of 1, 2, 3, 4, 5, 6, 7, and 8 m. The results showed that the rill erosion prediction model is applicable to rills on purple soil slopes with subsurface water flow at different depths. The effect of the slope gradient on the sediment concentrations is greater than that of the flow rate under various SWFDs. Slopes with shallower subsurface water flow depths from the soil surface produced higher soil erosion and sediment delivery, and the sediment concentrations of rill erosion under the impacts of SWFDs of 5, 10, and 15 cm from the soil surface were 61%, 50%, and 41% of that of the saturated soil slope, respectively. Moreover, the rill erosion process can be well simulated with sediment concentration data from 1 to 4 or 1–8 m rill lengths when the maximum sediment concentration at the sediment transport capacity level is determined. Our results provide a simplified and accurate method for predicting erosion processes with few data and reveal rill erosion processes under the effect of subsurface water flow. [ABSTRACT FROM AUTHOR]

This paper presents transport of a mixture of cohesive sediments and sand in the Paranagua Estuarine Complex in the south of Brazil. The estuary houses a navigation channel from the Atlantic Ocean to a busy harbour. The channel requires frequent dredging owing to sediment deposition to maintain navigable depth for vessels. A three-dimensional process-based model for sediment transport coupled with wave-current models based on the Delft3D modelling system is constructed for the estuary. Extensive field data concerning current velocity, water level, salinity and suspended sediment concentration were collected. The flow model that is necessary to run the sediment transport model was calibrated and validated using field measurements. In this paper only the results concerning the sediment motion are presented. Calibration and validation of the numerical model show that the results of sediment transport represent the field conditions well. Additional support for the validity of the computed results is provided by field data pertaining to bathymetry acquired in 2005 and 2006. The present study gives insight into the motion of cohesive sediments and the morphological behaviour of the estuary, and should help operators maintain the channel for navigation. [ABSTRACT FROM AUTHOR]

In this study an incompressible smoothed particle hydrodynamics (ISPH) approach coupled with the sediment erosion model is developed to investigate the sediment bed scour and grain movement under the dam break flows. Two-phase formulations are used in the ISPH numerical algorithms to examine the free surface and bed evolution profiles, in which the entrained sediments are treated as a different fluid component as compared with the water. The sediment bed erosion model is based on the concept of pick-up flow velocity and the sediment is initiated when the local flow velocity exceeds a critical value. The proposed model is used to reproduce the sediment erosion and follow-on entrainment process under an instantaneous dam break flow and the results are compared with those from the weakly compressible moving particle semi-implicit (WCMPS) method as well as the experimental data. It has been demonstrated that the two-phase ISPH model performed well with the experimental data. The study shows that the ISPH modelling approach can accurately predict the dynamic sediment scouring process without the need to use empirical sediment transport formulas. [ABSTRACT FROM AUTHOR]

Eroded sediment is an important feature of permanent gully's development; however, obtaining the specific characteristics of the sediment transport in the gully can be difficult. Thus, a composite fingerprinting technique, incorporating uncertainty analysis, has been employed to investigate the mean relative contribution of sediment sources in permanent gullies. In this study, 31 tracers were measured at 62 different sampling sites from three layers of a gully wall [surface layer (SL), sandy soil layer (SSL), and semi-weathering rock layer (SWL)] and 36 sediment samples from the slumping deposit and alluvial fan of the gullies. The sediment source tracing procedure was therefore used to assess the relative contribution of each source. The mean relative contribution from the SL to the sediment of the slumping deposit is higher in the active gully (G1), and is relatively lower in the potentially stable (G2) and stable gullies (G3); thus there was no obvious gully bank retreat in G2 and G3. In different places of the G1 alluvial fan, the mean relative contribution of the SL, SSL and SWL ranged from 9–11, 36–43 and 46–55%, respectively. However, the sediment contribution of the SL increased in G2 and G3 due to the changes in the erosion type. The mean relative contributions of the SL were 33 ± 5 (G2) and 30 ± 3% (G3). These findings have important implications for the establishment of a scientific basis for permanent gully sediment transport management and control policies. [ABSTRACT FROM AUTHOR]

The location of a wave farm and, in particular, its distance to the coast is one of the key aspects in a wave energy project. The effects of the farm on the coast, which can be instrumental in mitigating storm-induced erosion and thus contribute to coastal defence, are sometimes disregarded in selecting its location, possibly due to the inexistence of an ad hoc methodology. In this context, the objective of this work is to examine the influence of the farm-to-coast distance through a sensitivity analysis in a case study: Perranporth (UK). The impacts of a wave farm on the beach morphology are examined in four scenarios with different farm-to-coast distances using a high-resolution suite of numerical models. The results show that a wave farm closest to the beach offers the highest degree of coastal protection (up to 20% of beach erosion reduction). The downside of this enhanced coastal protection is that the wave resource available at this location would be slightly smaller (approx. 10%) than in the case of the wave farms further from the coast. More generally, we find that the farm-to-coast distance is a critical variable in determining the effectiveness of a wave farm for coastal defence. [ABSTRACT FROM AUTHOR]

An important part of planning for the rehabilitation of a mine site is the design of stable final landforms for waste rock dumps or spoil piles. Whilst able to be assessed over the short-term (years to decades), the longer term behaviour (centuries to millennia) of such landscapes is not within any meaningful human time frame of observation. Predictive numerical models, therefore, form an important tool with which current landscape behaviour and longer term trajectory can be assessed. However, an important issue associated with the use of models is the ability to assess the reliability and accuracy of the model. Here the SIBERIA and CAESAR-Lisflood Landscape Evolution Models (LEMs) are used to simulate and assess the geomorphic stability of a conceptual rehabilitated landform of the Ranger uranium mine in the Northern Territory, Australia, for a simulated period of up to 1000 years. Utilising both models in this study enabled an independent assessment of likely landscape processes and evolution as well as each model. Results show that SIBERIA and CAESAR-Lisflood produce erosion rates and patterns that are broadly similar. At millennial time scales, short-term processes such as gullying appear to be the dominant erosion features in the proposed landforms and may produce substantial erosion in terms of size and amount of hillslope material eroded and transported downslope. Vegetation was found to have a major effect on the erosion potential of the landform surface. Overall both models produce very similar results. [ABSTRACT FROM AUTHOR]

Ditch network maintenance in drained peatland forests increases sediment load and causes harmful effects on downstream watercourses. The objective of this study was to identify the immediate erosion processes in the ditch network and quantify the impact of the ditch network maintenance on suspended solids (SS) load at the catchment outlet. Ditch level processes were measured by conducting field campaigns and catchment-level responses were obtained by using the paired catchment approach. Measurements were conducted at two nested catchments in Koivupuro, Eastern Finland, where runoff and turbidity were monitored continuously at the catchment outlets and erosion and deposition were measured in selected ditches with a pin meter, erosion pins and sediment collectors. According to the results, the sediment load was at its highest during the first year after the ditch network maintenance and especially high during the first spring snow-melt period. Pin-meter measurements, sediment-collector data and results of ditch-bed erosion pins showed that the erosion was more severe in the ditch cut into mineral subsoil than in the ditch cut into thick peat. The SS load from the whole Koivupuro catchment during the first year after the ditch network maintenance was, depending on the estimation method, 185 or 250 kg treated-ha −1 a −1 (0.56 or 0.75 kg ditch-m −1 ), while the net erosion within the ditch network was much higher, 6300 kg treated-ha −1 a −1 (19 kg ditch-m −1 ), indicating that suspended solids were deposited before reaching the outlet of the catchment. Compared to the earlier studies which have focused on the catchment-level effects of ditch network maintenance on the SS loads, the current study succeeded in showing erosion processes and their variability within the ditch network and provided information for improving water protection during ditch network maintenance. [ABSTRACT FROM AUTHOR]

Nearshore submerged structures made of sand-filled geosystems are an interesting use for this type of coastal protection technology. These systems have an advantage over more traditional materials such as concrete units or rock, which is the limited and non-permanent impact on natural coastal processes. On top of that are also some important research achievements and improvements at the level of the materials. However, at more exposed hydraulic conditions under high wave energy its application is still hampered by the lack of knowledge about their performance. This paper describes research results based on a series of laboratory measurements of the hydrodynamic and morphodynamic change produced in the vicinity of submerged nearshore structures. An analysis of the different model outputs produced, with respect to sediment transport, wave reflection and wave-induced pressures, has been made and is discussed throughout the paper. Such a comparative analysis provides insights into the efficiency of each defence scheme in maintaining a beach and in protecting the shoreline. The sand-filled geosystems as nearshore submerged structures proved to be efficient in retarding the offshore movement of sediments and in maintaining the shoreline, even if instabilities due to elements' displacement and local scour have been observed. [ABSTRACT FROM AUTHOR]

Erosion rates along Alaska's Beaufort Sea coast, among the highest in the world, are negatively impacting communities, industrial and military infrastructure, and wildlife habitat. Decreasing maximal winter ice extent and increasing summer open water duration and extent in the Beaufort Sea may be making the coast more vulnerable to destructive storm waves than during recent, colder, icier decades. Previous studies of Beaufort Sea coastal change have been limited to subaerial analyses of the shoreline. Here we describe nearshore seafloor change by comparing post-World War II (WWII) (1945-53) bathymetry data to recently acquired (1985–2018) bathymetry data and relate the observed seafloor change to adjacent shoreline change near Utqiagvik, within Stefansson Sound, and immediately west of Barter Island and Kaktovik. Within the Utqiagvik region, seabed erosion was generally highest (>1.0 m of loss) offshore of Point Barrow and along the eastern end of the Tapkaluk Islands, while there were lesser amounts of deposition (<0.5 m of gain) within the protected waters of Elson Lagoon. Sedimentation was generally highest offshore of Point Barrow, in a region of converging currents, and on the landward side of the barrier islands and spits fronting Elson Lagoon, which is likely related to a regional trend of westerly sediment transport and landward migration of the barrier islands. Within Stefansson Sound, perhaps the most notable changes from post-WWII bathymetry data compared to recent data are a switch from mixed, low erosion and deposition in 1997 to low deposition (<0.5 m) in 2018 east of the Boulder Patch, a switch from low erosion in 1997 to neutral depth change in 2018 in the channel between the north and south Boulder Patch areas, and higher deposition from 1997 to 2018 landward of the rapidly retreating barrier islands along the Sound's northern border. At Barter Island, high erosion near north-facing shorelines and high deposition near west-facing shorelines generally matched shoreline changes. One of our goals is to identify possible processes responsible for the depth changes we quantified. Using simple metrics that relate sediment characteristics with modeled waves and non-wave induced currents, we show that sediment resuspension and transport by both wave and non-wave driven currents likely contribute to the overall patterns of change within the ∼13 m isobath along the open coast, and that the influence of wave action affecting sediment transport is expanding seaward. • Patterns of decadal-scale changes in shoreline positions and bathymetry indicate possible linkages within the nearshore. • Depth changes are additionally driven by sediment resuspension and transport by both wave and non-wave driven currents. • Wave action affecting sediment transport expanded seaward and deepened by as much as 15 cm/yr between 1979 and 2019. [ABSTRACT FROM AUTHOR]

• SWAT hydrological model has high potential in the assessment of watershed changes. • Land use changes caused by forest fires affect hydrological response of watershed. • Significant increase in surface runoff and sediment load in the post-fire scenario. • Sediment yield increased by 6.5 times with the highest fire spatial distribution. • Forest fire scenarios help to limit hydrological impacts of fire on sediment load. Forest fires profoundly affect the nature of watershed responses to precipitation, increases in runoff rate and volume, and post-fire sediment discharge. A post-fire watershed assessment to identify potential trouble spots for soil erosion and flooding can help land managers for decision-making on deploy mitigation, remediation measures, and restoration action plans. Predicting the potential impact of fires on runoff and soil erosion requires distributed hydrological modeling methods. This study used the Soil and Water Assessment Tool (SWAT), a rainfall-runoff model, to investigate the hydrological consequences of forest fires and their impact on sediment load under different burnt scenarios. For the pre-fire (baseline) scenario, the watershed is calibrated by using the measured discharge and suspended sediment concentration data from the weather station during the time step to estimate post-fire changes at the sub-catchment scale. The total water and sediment yield for the selected sub-catchment in the post-fire scenario with the highest spatial distribution of forest fire, due to the excessive surface runoff (an increase of 14.5%) increased significantly, resulted in 6.5 times increase in sediment yield. The results obtained from the study indicate a significant increase in sediment transport into the stream in the post-fire scenario. A large volume of soil losses occurred during the time step. In contrast, due to removing trees and vegetation from the ground, less evapotranspiration and infiltration occurred in selected sub-catchment areas after forest fires. In terms of watershed management, understanding the consequences of forest fires on hydrological services will be an effective method for sediment budget control. Therefore, applying the rainfall-runoff and erosion models for the watershed with developing plausible forest fire scenarios can be a productive method to deal with the threats and hydrological risks such as soil erosion and sediment transfer to the downstream environment. [ABSTRACT FROM AUTHOR]

Coastal zones are vulnerable to both erosion and flood risk, which can be assessed using coupled hydro-morphodynamic models. However, the use of such models as decision support tools suffers from a high degree of uncertainty, due to both incomplete knowledge and natural variability in the system. In this work, we show for the first time how the multilevel Monte Carlo method (MLMC) can be applied in hydro-morphodynamic coastal ocean modelling, here using the popular model XBeach, to quantify uncertainty by computing statistics of key output variables given uncertain input parameters. MLMC accelerates the Monte Carlo approach through the use of a hierarchy of models with different levels of resolution. Several theoretical and real-world coastal zone case studies are considered here, for which output variables that are key to the assessment of flood and erosion risk, such as wave run-up height and total eroded volume, are estimated. We show that MLMC can significantly reduce computational cost, resulting in speed up factors of 40 or greater compared to a standard Monte Carlo approach, whilst keeping the same level of accuracy. Furthermore, a sophisticated ensemble generating technique is used to estimate the cumulative distribution of output variables from the MLMC output. This allows for the probability of a variable exceeding a certain value to be estimated, such as the probability of a wave run-up height exceeding the height of a seawall. This is a valuable capability that can be used to inform decision-making under uncertainty. • First use of MLMC (multilevel Monte Carlo) with a coupled hydro-morphodynamic model. • Large drop in computational cost for same accuracy using MLMC instead of Monte Carlo. • Determine the distribution of variables of interest in coastal zone cases using MLMC. [ABSTRACT FROM AUTHOR]

The new toolbox ScourApp is presented and applied for analysis of the complex interactions between local scour and sediment deposition at bridges during floods and to determine the relative importance of the controlling parameters on scour depth. ScourApp represents the time-dependent sediment transport processes through modern empirical formulations to compute the evolution of scour depth at a bridge pier. Results show that the mathematical model reproduces observed scour depths with high accuracy and confirm that ScourApp is a suitable tool for scour analysis. The model parameters controlling the time dependent scour depth were the equilibrium scour depth, and two constants representing the effects of pier geometry, flow and sediment. Sensitivity analysis showed that all three scour model parameters exhibited a nearly linear relation with the final scour depth. Moreover, results considering sediment deposition obtained for the Rapel Bridge showed that scour depths are highly sensitive to the sediment supply rate. ScourApp is recommended in scour assessment for bridge planning, design, management, and forensic analysis, as well as for engineering education. • The open-source toolbox ScourApp for scour analysis is developed. • Complex interactions of time-dependent scour and scour hole refilling are analysed for several laboratory and real-life cases. • The relative importance of controlling parameters on scour is analysed. [ABSTRACT FROM AUTHOR]

Understanding how subaqueous sediment gravity flows (SSGF) evolve in time and space, and how their deposits vary spatially, is a key research focus for gravity flow sedimentology. This study investigates depositional facies, depositional elements, and sediment transport processes of supercritical flows and hybrid event beds (HEBs) of the Lingshandao Formation in Lingshan Island, Eastern China. Three kinds of depositional elements were recognized: mass transport deposits (MTDs), channel-lobe transition zone (CLTZs), and lobe complexes. MTDs can be sub-divided into proximal and distal deposits. CLTZs are characterized by facies changes from massive coarse-grained pebbly sandstone to backset bedding sandstone in a down-slope direction, which are the deposits of supercritical turbidity currents. HEBs are common in both proximal and distal lobe settings. Tripartite structure in HEBs, which may be caused by up-slope substrate erosion, implies a relatively proximal origin compared with bipartite HEBs, perhaps caused by fluid fractionation in the research area. The succession is formed by a prograding lobe unit, followed by MTDs which are themselves overlain by deposits from a CLTZ. This vertical stacking pattern implies the potential longitudinal facies tract from CLTZ; to lobe complex deposits, is accompanied by emplacement of MTDs at the slope break. The flow types accompanied by sediment transport processes imply that erosion by supercritical turbidity currents associated with a hydraulic jump in the channel-lobe transition zone may be the main reason for mud-clasts and matrix addition to the flow. The large-scale addition of mud-clasts and suspended mud may dampen turbulence in proximal to medial lobe settings, and result in medium-to thick-bedded HEBs with common erosional features and tripartite structures. The remaining suspension flow (with abundant mud) may further transport down-dip and form medium-to thin-bedded HEBs with bipartite structures and rare mud-clasts. These findings may be applicable to other SSGF systems with supercritical flow deposits and hybrid event beds, emphasizing the downdip and lateral variation in depositional elements associated with gravity flow evolution. • CLTZs are characterised by bypass lags, backset bedding, cut-and-fill deposits, soft sediment deformation structures. • The erosion by supercritical turbidity currents caused mud matrix and clasts being added to the flow, and result in HEBs. • Vertical distribution represents the longitudinal sediment transport processes from CLTZ to lobe complex deposits. [ABSTRACT FROM AUTHOR]

• Changes in spatial variation of rock fragment contents (SVRFC) due to tillage altered hydrological and erosional processes. • Yields of subsurface flow and deep percolation increased with decreasing SVRFC. • The decreasing SVRFC caused a decrease in surface erosion, but an increase in subsurface erosion. • Effects of rainfall intensity on hydrological and erosional processes were associated with SVRFC. Cultivation activities play an important role in shaping the spatial distribution of rock fragments in hilly agricultural landscapes. The spatial variation in rock fragment contents (SVRFC) can exert strong effects on the spatial heterogeneity of soil properties with great implications for hydrological fluxes and soil erosion. However, previous research always assumed that rock fragments were homogenously distributed, but little has been known concerning the SVRFC over the hillslope and its influence on hydrological and erosional processes. In this study, simulated rock fragment contents (RFCs) in soil layers at the upper (0.6 kg kg−1) and lower slope positions (0, 0.2, 0.4 and 0.6 kg kg−1) were established in combination with artificial rainfall experiments, to investigate the influence of RFC difference between the upper and lower slope positions on hydrological and erosional processes. Results show that the decreasing RFC difference reduced the yield of surface flow (5–100%), but increased yields of subsurface flow (58–792%) and deep percolation (19–130%). Additionally, the decreasing RFC difference reduced the runoff velocity of surface flow and surface erosion rate, but aggravated subsurface erosion. Especially under the 0 kg kg−1 RFC difference, the intense soil loss occurred at the subsurface which may be due to the highly developed preferential flow. With increasing rainfall intensity, great increments in yields of subsurface flow, deep percolation and subsurface sediments were found under the small RFC difference which had small increments in yields of surface flow and surface sediments. These results suggest that the changing SVRFC related to tillage erosion can exert strong influence on behaviors of hydrological and erosional processes. Our study provides a better understanding of the interaction between agricultural cultivation and soil–water loss in hilly agricultural landscapes. [ABSTRACT FROM AUTHOR]

The field observation at two neighboring beaches showed significant effects of berm height on beach profile changes during a major storm. The fully nonlinear Boussinesq wave model, FUNWAVE-TVD, with a sediment transport module was used to simulate the beach erosion processes of the two beaches. The model reproduced the beach profile changes in good agreement with the measured data. The model results revealed that, for the beach with a higher berm, the wave force, wave-induced undertow flow, along with the higher sediment concentration on the berm induce more offshore sediment transport and cause significant beach profile changes compared to the beach with a lower berm. The erosion trend with different berm heights was predicted by using a series of numerical tests with different berm heights and offshore forcing conditions. The test results suggested that beach erosion increases with the berm height until the berm height reaches a certain level. • Field observation erosion/deposition shows pattern different storm-induced between two neighboring beaches. • The sediment module in the Boussinesq model, FUNWAVETVD, is validated against measured morphological data for the first time for the wind wave conditions. • Trend of beach erosion with different heights of beach berm is investigated. [ABSTRACT FROM AUTHOR]

Abstract: While previous studies have documented contaminants in fish, sediments, water, and wildlife, few specifics are known about the spatial distribution of contaminants in the Columbia River Estuary (CRE). Our study goal was to characterize sediment contaminant detections and concentrations in reaches of the CRE that were concurrently being sampled to assess contaminants in water, invertebrates, fish, and osprey (Pandion haliaetus) eggs. Our objectives were to develop a survey design based on sedimentation characteristics and then assess whether sediment grain size, total organic carbon (TOC), and contaminant concentrations and detections varied between areas with different sedimentation characteristics. We used a sediment transport model to predict sedimentation characteristics of three 16km river reaches in the CRE. We then compartmentalized the modeled change in bed mass after a two week simulation to define sampling strata with depositional, stable, or erosional conditions. We collected and analyzed bottom sediments to assess whether substrate composition, organic matter composition, and contaminant concentrations and detections varied among strata within and between the reaches. We observed differences in grain size fractions between strata within and between reaches. We found that the fine sediment fraction was positively correlated with TOC. Contaminant concentrations were statistically different between depositional vs. erosional strata for the industrial compounds, personal care products and polycyclic aromatic hydrocarbons class (Indus–PCP–PAH). We also observed significant differences between strata in the number of detections of Indus–PCP–PAH (depositional vs. erosional; stable vs. erosional) and for the flame retardants, polychlorinated biphenyls, and pesticides class (depositional vs. erosional, depositional vs. stable). When we estimated mean contaminant concentrations by reach, we observed higher contaminant concentrations in the furthest downstream reach with a decreasing trend in the two upstream reaches. Contaminant survey designs that account for sedimentation characteristics could increase the probability that sampling is allocated to areas likely to be contaminated. [Copyright &y& Elsevier]

Abstract: Sediment transport processes in rivers continue to pose a challenge when designing movable-bed physical models, particularly for reproducing the grain sorting and bank erosion (fluvial erosion and mass failure). This paper presents and discusses scale effects of a specific scaling approach for multi-grain size mixtures that preserves similarity of initial motion for each grain size class and of the bank stability coefficient between the model and the prototype, but relaxes strict similarity of the Shields and particle Reynolds numbers. This approach is appropriate when bed load transport near incipient motion conditions is being studied, and allows for larger grain size scales than when full Shields parameter similarity is enforced. As part of an environmental project to rehabilitate sediment transport through bank erosion, this method has been applied to scale a Froude number criterion physical model of a reach of the Old Rhine (France). This has resulted in an undistorted scale of 40, and the use of sand as the model bank material. Each grain size has a different geometrical scale. The time scale for sediment motion is grain size and flow discharge dependent. An average time scale of 6 has therefore been used (four model hours = one prototype day). A strategy devised for the field case consists of two higher, larger island groynes that replace the three existing groynes, producing bank erosion for flow rates below the mean annual flow rate. Extrapolation of model behaviour to the prototype is not a major problem, but the volume of eroded bank material may be underestimated, mainly because of the relaxation of the Shields number similarity and the apparent cohesive properties of the model bank material. [Copyright &y& Elsevier]

Abstract: Physically-based, catchment scale sediment delivery models have become increasingly complex, sophisticated and are suitable for a diverse range of environmental contexts. However, in their attempts to best represent the physical processes of erosion and deposition, these models require large and detailed input datasets. When such data are unavailable, annual sediment yield models are relied upon. However, in this class of models, widely available data such as daily precipitation and discharge are disregarded resulting in a reduction in temporal accuracy. To fill this scientific and management gap, the landscape evolution model LAPSUS was adapted (LAPSUS-D) for a meso-scale catchment to model sediment yield on a daily resolution. The water balance component within the model enables the calibration of the model in terms of water discharge with measured daily discharge at the outlet. This methodology is especially important when modeling sediment yield from catchments which are ungaged catchments in terms of sediment, but where hydrological data are available. As the simulation of sediment yield was the main objective of the study, the calibration focused on peak discharge. The focus on peak discharge provides insight into the capability of the model to generate, route and deliver sediment at the outlet of a meso-scale catchment. LAPSUS-D has daily temporal resolution and requires a 10 to 30m pixel size DEM, soil map, land-use map and daily hydrological records (precipitation and discharge). In this paper we present the first assessment of the hydrological model performance and an analysis of the sensitivity of the model to input parameters. Our study site is a 23-km2 catchment in Upper Nysa Szalona, southwest Poland with temperate climate. Results show that the model can reliably predict peak discharge, which is expected in future studies to allow reliable estimates of sediment transport capacity, redistribution and yield. [Copyright &y& Elsevier]

Highlights: [•] Hyperconcentrated flood peak is observed to increase downstream in the Yellow River. [•] Fully coupled modeling predicts peak increase with sediment effect on bed friction. [•] Bed friction decrease is more important than erosion for the peak increase. [•] Channel storage change reconciles bed friction and erosion to explain the increase. [•] The downstream flood peak increase may occur with channel storage reduction. [ABSTRACT FROM AUTHOR]

Abstract: In this study a three-dimensional sediment transport model was developed. The model accounts for both current and wave forcing on the sediment and was implemented over the Gulf of Lions. A two-way nesting technique was used to focus on the Rhone River prodelta which is considered as a sink for riverine sediment. In addition, to understand the resuspension of trapped sediment over the Rhone prodelta, an in situ experiment, called SCOPE, was conducted during the winter 2007–2008. The experiment consisted of measuring hydro-sedimentary parameters using a mooring station comprising a current profiler (ADCP) and an altimeter (acoustic transducer) located in the eastern part of the Rhone prodelta. The three-dimensional transport model was validated using these data, and used to investigate the effect of sediment dynamics at the prodelta and Gulf of Lions scale. Both modelling and data analysis highlighted the impact of the two strong storms from the south-east which characterised the experimental period. Erosion of bed material (about 2cm) and an increase in suspended material (up to about 50–100mg/l) in the water were the result of each storm as recorded at the mooring station. The erosion capacity due to waves, combined with a strong current, due to both wind and wave forcing, resulted in strong south-westward export over the whole prodelta. Each storm was responsible for an off-prodelta export estimated at around 2.1Mt. This study demonstrates that the Rhone River sediments trapped over the Rhone prodelta are subject to strong resuspension during episodic events. [Copyright &y& Elsevier]

Abstract: Thus far various numerical models have been developed and improved to aid understanding of the sediment transport process due to tsunamis. However, the applicability of these models for the field-scale bathymetric change remains a major issue due to the scarcity of measured bathymetric data immediately before and after tsunamis. This study focuses on assessing the applicability of the sediment transport model by comparing the model results with measured bathymetry data obtained one month before and two months after the 2004 Indian Ocean tsunami at Kirinda Fishery Harbor, Sri Lanka. Obtained model results were compared with measured data along four different transects. In particular, similar to the measured data, the model reproduced the bed level change at the harbor mouth well, although it shows some discrepancy on bathymetric change along the shoreline, which is directly affected by littoral drift. Therefore, it is noted that the divergence of reproducing the local bathymetry change is due to the normal wind wave effect on measured data and the model limitations. Hence we included the wind wave effect in modeled data and the discrepancy between measured and modeled data was reduced. Furthermore, the modeled bed level change indicates a dynamic behavior in terms of the net variation during the tsunami flow, such that deposition dominates in the inflow and erosion dominates in the backflow. Both bed level variation and the suspended load concentration reveal that the large amount of eroded sediment attributable to tsunami waves was in suspended form and was deposited in the nearshore area after the water fluctuation had abated. The model results further indicate that eroded sediment at the initial depth deeper than 11m might be brought by the incoming tsunami waves and deposited in the nearshore area where the depth is shallower than 7m. [Copyright &y& Elsevier]

Wind waves breaking at an angle with the shoreline force the drifting of littoral sediments, which is known for contributing to the formation and growth of barrier spits. Intriguingly, increased rates of longshore wave power have also been associated with the erosion of some barrier spits on the updrift margin of tidal inlets. Therefore, a numerical experiment was designed and is presented here, which investigates the possible links between the longshore wave power and the shortening of these elongated coastal barriers. Based on a process-based model, the experiment provides new insights into the forces at play in the redistribution of sediments between a sandspit and its adjacent inlet, respectively the Cap Ferret and the Bay of Arcachon's tidal inlet, in SW France. More particularly, model scenarios were defined that show how combined waves and tide create gradients of residual sediment transport responsible for a sediment deficit at the spit – inlet boundary. The deficit was also found to deepen with increasing longshore wave energy, as if the transfer of sediment from the spit to inlet shoals was accelerated. This physically explains the previously observed retreat of the spit's distal end during periods dominated by the positive phase of North Atlantic Oscillation (NAO) in winter. Indeed, according to model results, higher and/or more oblique waves associated with the positive phase of the NAO are expected to increase the transfer and storage of the drifting sediments to and by the inlet shoals, and this at the expense of the spit. While these conclusions remain valid, we noticed that the sensitivity of model results to the bottom friction enhanced the importance of accurately representing the spatio-temporal distribution of bed roughness when investigating the morphodynamic interactions between real-world tidal inlets and their margins. • Residual sediment transport is modelled at a mixed energy tidal inlet. • Waves with tides create transport gradients near the inlet's updrift spit extremity. • Larger or more oblique waves deepen this gradient and reinforce the sand deficit. • Physically sounded explanation to enhanced spit erosion during NAO + winters. • Bed roughness models need to be improved for 2DH inlet-spit morphodynamic modelling. [ABSTRACT FROM AUTHOR]

The flow routing module in several large-scale erosion and sediment transport models generally adopts simplifications that ignore important physical aspects of river dynamics. In this study we compare for the first time the results generated by a large-scale erosion and sediment transport model, using two different flow routing approaches: a combined Saint-Venant and Muskingum-Cunge method and the Inertial flow routing. For this assessment, simulations are performed with the MGB-SED model. We evaluate sediment characteristics such as suspended sediment load and concentration, floodplain effects, and the flux of suspended sediment within the Madeira River basin. The simulation with the inertial approach presents satisfactory results, similar to those achieved with the combined Saint-Venant approach for lowland rivers and the Muskingum-Cunge method for steeper rivers. Also, Inertial module is capable to represent the complex processes of the basin, but with easier preprocessing and numerical features, thus promising expanded capabilities for large-scale simulations. • Evaluation of the relative weights of the Saint-Venant equation terms. • Large-scale sediment model using inertial flow routing method. • The average percentage that is represented by the advective inertial term is 0.15%. • Similar results were achieved with full Saint-Venant equations for lowland rivers. [ABSTRACT FROM AUTHOR]

• Upslope sediment-laden flow caused additional erosion in ephemeral gully zone. • Transport-dominated sediment regime was found under filed and laboratory conditions. • An increase in sediment concentration of inflow decreased downslope soil erosion rates. • Laboratory simulations verified the field monitoring results for extreme rainfall events. Ephemeral gully (EG) is an important linear erosion feature, often occurring at mid-slope position, that can be greatly influenced by upslope inflow and its sediment transport capacity. How sediment concentration in upslope inflow influences downslope EG erosion is still unclear. Thus, field monitoring on a natural hillslope and indoor simulations on a dual-box system were conducted to better understand their relationship. The results showed that both field monitoring and indoor simulation displayed the additional sediment delivery caused by upslope sediment-laden flow, verifying the transport-dominated sediment regime in EG systems. In field observations, the sediment increment coefficient (SIC , ratio of net sediment delivery caused by upslope sediment-laden flow to the total sediment delivery) on an event scale varied from 4.6% to 88.6%. In indoor simulations, the SIC changed from 24.9% to 87.5%. Indoor simulation experiments with a range of 0–378.2 g L−1 sediment concentration supplied by a feeder box, showed that SIC linearly decreased as sediment concentration of upslope inflow increased. Field monitoring showed complicated phenomenon because of natural random variations. For rainfall events with PI 30 (the product of precipitation and maximum 30-minute rainfall intensity) larger than 400 mm2 h−1 (similar to the designed extreme rainfall in laboratory simulations), SIC also generally decreased as sediment concentration of upslope inflow increased, especially when sediment concentration of upslope inflow was smaller than 400 g L−1. Thus, laboratory simulations verified the field monitoring results of extreme rainfall events with large rainfall amounts and intensities. This study illustrated the necessity of in-situ field monitoring and indicated that design of indoor simulation experiments needs more comprehensive considerations on complicated hydrological and sediment conditions. [ABSTRACT FROM AUTHOR]

Two barrier systems in southeastern Tasmania afford the opportunity to contrast Holocene barrier evolution and explore large-scale coastal morphodynamics under consistent regional-scale boundary conditions on an embayed wave-dominated coastline. New Optically Stimulated Luminescence (OSL) ages for the previously undated seaward ridges of Seven Mile Beach constrain the deposition of the foredune ridges over the past ~1000 years indicating continued shoreline progradation at ~0.4 m/yr. A further 13 OSL ages collected from the foredune ridges of Nine Mile Beach barrier detail the evolution of this barrier system and indicate progradation commenced approximately ~8500 years ago. Following this, a steady rate of shoreline advance at 0.14 m/yr was evident to near present-day with one phase of rapid accretion ~5000 years ago. This occurred as the barrier system extended eastward to span the full embayment width which resulted in the redirection of the estuarine channel and the subsequent erosion of previously deposited ridges due to channel migration likely over several thousand years. The eroded sediment may have contributed to ongoing positive sand budget in the embayment and continued shoreline progradation. Barrier 'recycling' was also suggested as a potential driver of progradation at Seven Mile Beach based on the truncated margin of the landward ridges. However, at both sites, the dynamics of possible sediment exchange between the back-barrier and open shoreline requires further detailed modelling. The relatively small river systems in this region supply minimal sand to the coast at these sites, however, there is some minor alongshore sediment supply along the western margin of these deep embayment's. In light of this, these two barrier systems demonstrate the importance of internal morphodynamic thresholds and cross-shore sediment exchange from the shoreface as key drivers of barrier evolution and large-scale coastal change in embayed coastal settings. • Holocene barrier deposition in Tasmania was driven by onshore sediment transport. • Shoreline advance at Nine Mile Beach averaged 0.14 m/yr from 8500 years to present. • Erosion of inner margin of the barrier may have augmented sediment budget. • Large-scale coastal behaviour is explained by internal morphodynamic thresholds. [ABSTRACT FROM AUTHOR]

It has been proposed that at short timescales of 102–105 yr, climatic variability can explain variations in sediment flux, but in orogens with pronounced climatic gradients rate changes caused by the oscillating efficiency in rainfall, runoff, and/or sediment transport and deposition are still not well-constrained. To explore landscape responses under variable climatic forcing, we evaluate time windows of prevailing sediment aggradation and related paleo-erosion rates from the southern flanks of the Dhauladhar Range in the western Himalaya. We compare past and present 10Be-derived erosion rates of well-dated Late Pleistocene fluvial landforms and modern river sediments and reconstruct the sediment aggradation and incision history based on new luminescence data. Our results document significant variations in erosion rates ranging from 0.1 to 3.4 mm/yr over the Late Pleistocene. We find that, during times of weak monsoon intensity, the moderately steep areas (hillslope angles of 27 ± 13°) erode at lower rates of 0.1–0.4 mm/yr compared to steeper (>40°) crestal regions of the Dhauladhar Range that erode at 0.8−1.3 mm/yr. In contrast, during several millennia of stronger monsoon intensity, both the moderately steep and high slope areas record higher erosion rates (>1-3.4 mm/yr). Lithological clast-count analysis shows that this increase of erosion is focused in the moderately steep areas, where Lesser Himalayan rocks are exposed. Our data thus highlight the highly non-linear response of climatic forcing on landscape evolution and suggest complex depositional processes and sedimentary signals in downstream areas. • Paleo-erosion rates in the Himalaya are modulated by climate forcing. • Erosion rates are higher during episodes of strong monsoon. • Topographic response to climate change is non-linear. • Rapid erosion during short-lived strong monsoon phases result in valley aggradation. [ABSTRACT FROM AUTHOR]

Multi-purpose Artificial Reefs (MPARs) are structures that may provide aesthetically acceptable coastal protection and improve recreational outcomes. Twenty years after construction of the first MPAR, Narrowneck Reef on the Gold Coast of Australia, most of the available literature is still focused on the planning, design and construction of such structures and peer-reviewed publications on their post-construction monitoring, interaction with sediment transport and impacts on coastal morphology are lacking. The aim of this paper is to evaluate how does Narrowneck Reef influence the sediment transport, and morphological changes around the anthropogenic structure, two decades after construction. To do so, a combination of ten high spatial resolution topo-bathymetric surveys from the top of the dune to the 10 m depth captured over 21 months and a series of 60 simulations using a calibrated numerical model were used. Our results demonstrate that: although not expected during design or reported in similar structures, sand can bypass the MPAR around its offshore end; under oblique waves, the longshore currents are deflected as they pass the reef, resulting in a shadow zone on the downdrift side where sand deposits; the bar crest tends to be higher on the reef's updrift side compared to downdrift, indicating that the MPAR can act as a store for sediments, as initially designed. Furthermore, the MPAR can act to stabilise the bar as it moves onshore with a downdrift offset of the inner bar as a result of low oblique wave incidence. The results presented here demonstrate that the short-term response to the MPAR twenty years after construction is more closely related to the updrift build up of sand and the deflection of longshore currents as they encounter the reef than to the dissipation of wave energy. This is because MPARs are designed to dissipate just enough wave energy so that they can achieve their recreational goal (surfing). • Beach morphodynamic state and tide level influence sediment transport pathways. • Sand bypassing occurs mainly inshore of the structure. • Under large oblique waves, sand bypass can occur offshore of the structure. • Deflection of longshore currents influence morphological response to the reef. • Bar crest is usually higher on the reef's updrift side compared to downdrift. [ABSTRACT FROM AUTHOR]

Earthworms are ecological engineers that play an important role in hydrological processes and soil erosion by their burrowing and casting activities. Little is known, however, about the ecological function of the activities of an anecic species (Metaphire guillelmi) from the Loess Plateau in China where the soil is severely eroded. We conducted rain-simulation experiments on artificial slopes (mesocosms) filled with soil from Loess Plateau. Two rain intensities (90 and 120 mm h−1) and slope gradients (5° and 15°) were used to investigate the influences of earthworm activity on runoff and soil loss under multiple conditions. Data from 15 d of earthworm activity and 1 h of rain indicated that earthworm activity significantly reduced runoff but aggravated soil erosion. Runoff initiation time increased 2.7–3.1-fold, contributing to the promotion of water infiltration, and the amounts and rates of runoff were 35.8–61.6% and 35.1–60.8% lower under earthworm activity than the controls, respectively. Earthworms greatly influenced the physical and chemical properties of the soil, and these properties were strongly correlated with runoff initiation time and cumulative runoff. The surface casts produced by the earthworms on the soil surface were completely dispersed, increasing the cumulative sediment by a maximum of 169%. Both rain intensity and slope gradient greatly influence runoff and soil detachment, but with earthworm activity, slope gradient was more influential due to its superior contribution to sediment transport. This study quantified the effects of M. guillelmi on runoff and soil erosion and provides basic data for developing a more integrated control of soil erosion on the Loess Plateau. • The increase in infiltration related to earthworm activities decreases runoff. • Soil erosion is aggravated by the low stability of surface cast under intense rainfall. • Earthworm impact on soil loss is larger at lower rain intensity and steeper slope. [ABSTRACT FROM AUTHOR]

Highlights: [•] Enlargement of semiarid streams was significantly correlated to urban development. [•] Increased sediment-transport capacity is a key predictor of enlargement. [•] ∼1.2:1 Proportionate channel enlargement with increased sediment-transport capacity. [•] Enlargement increased with distance to downstream grade-control features. [ABSTRACT FROM AUTHOR]

Abstract: The erosion and transport of sediments allow us to understand many activities of significance, such as crust evolution, climate change, uplift rates, continental processes, the biogeochemical cycling of pollutants and nutrients. The Amazon basin of Peru has contrasting physiographic and climatic characteristics between the Andean piedmont and the plains and between the north and south of the basin which is why there are 8 gauging stations located along the principal rivers of the Andean piedmont (Marañón, Huallaga, Ucayali) and the plain (Marañón, Tigre, Napo, Ucayali and Amazon rivers). Since 2003, the ORE-Hybam (IRD-SENAMHI-UNALM) observatory has performed out regular measurements at strategic points of the Amazon basin to understand and model the systems, behavior and long-term dynamics. On the Andean piedmont, the suspended yields are governed by a simple model with a relationship between the river discharge and the sediment concentration. In the plain, the dilution effect of the concentrations can create hysteresis in this relationship on a monthly basis. The Amazon basin of Peru has a sediment yield of 541 *106 t year−1, 70% comes from the southern basin. [Copyright &y& Elsevier]

Abstract: River bank erosion is the main process in small mountainous basins, especially those where the main channel is built of poorly resistant sedimentary rock or alluvium, exemplified by the Słomka basin. The main goal of the study, based on the field survey work and the erosion pin method, was to define the relation between river bank erosion, accumulation, and sediment transport. The investigations were carried out in the Słomka stream basin (watercourse length of 25.2km, basin area of 69.9km2) on an ~1.0-km-long stream reach, strongly anthropogenically transformed, between watercourse kilometres 5.0 and 6.0. We found that with an increase in flow the retreat bank rate increased nonlinearly. An average migration rate of the undercut banks ranged from 0.10m for the flow rate of 11.5m3 s−1 to 0.92m for the flow rate of 35.5m3 s−1. The maximum observed rate exceeded 0.8m for the flow rate of 11.5m3 s−1 and 9.0m for the flow rate of 24.8m3 s−1. With respect to the channel vertical morphology over the whole measurement section, we found that bed gradeline was raised, on average, by ~0.04m. The trend is contrary to the results of field surveys performed earlier on the Carpathian watercourses. The phenomenon is related to the abundant supply of rock rubble into the stream channel. High flow stages in the Słomka stream, which caused the stream bed material to move, had a predominant impact on stream channel morphology. Processes such as destructive activity of rain drops, aeolian erosion (sandblasting), soil expansion, and shrinkage during the rainy and dry seasons were of minor significance. [Copyright &y& Elsevier]

Abstract: Present-day sediment distribution offers a potentially strong constraint on past ice sheet evolution. Glacial system models (GSMs), however, cannot address this constraint while lacking appropriate representations of subglacial sediment production and transport. Incorporating these elements in GSMs is also required in order to quantify the impact of a changing sediment cover on glacial cycle dynamics. Towards these goals, we present a subglacial process model (hereafter referred to as the sediment model) that incorporates mechanisms for sediment production, entrainment, transport, and deposition. Bedrock erosion is calculated by both Hallet''s and Boulton''s abrasion laws separately, and by a novel quarrying law parametrized as a function of subglacial cavity extent. These process-oriented erosion laws are compared against a simple empirical relationship between erosion rate and the work done by basal stress. Sediment entrainment is represented by Philip''s law for regelation intrusion and soft-bed deformation is included as a subglacial sediment transport mechanism. The model is driven by the data-calibrated MUN (3D) GSM and a newly developed subglacial hydrology module. The sediment model is applied to the last North American glacial cycle and predicts sediment thickness and cumulative erosion patterns. Results are obtained in the context of a sensitivity analysis and are compared against the present-day distribution of glacigenic sediment and geological estimates of Laurentide Ice Sheet erosion. Given plausible ranges for the sensitivity parameters, chosen a priori based on available literature or on heuristic arguments, the calculated erosion depths overlap with the geological estimates of Laurentide erosion. Most of the runs in the sensitivity set produce unrealistically thick and continuous moraines along the eastern, southern and western margins of the North American ice complex, which suggests that the model overestimates sediment entrainment and thus englacial transport. A realistic sediment distribution is only obtained when the entrainment rate is capped at the average basal melting rate, which suggests that modelled entrainment and basal melting rates should be of the same order of magnitude. [Copyright &y& Elsevier]

Abstract: A computational investigation is presented of mono-, bi-, and polydisperse lock-exchange turbidity currents interacting with complex bottom topography. Simulation results obtained with the software TURBINS are compared with laboratory experiments of other authors. Several features of the flow, such as deposit profiles, front location, suspended mass, and runout length, are discussed. For a monodisperse lock-exchange current propagating over a flat surface, we investigate the influence of the boundary conditions at the streamwise and top boundaries, and we generally find good agreement with corresponding laboratory experiments. However, we note some differences with a second set of experimental data for polydisperse turbidity currents over flat surfaces. A comparison with experimental data for bidisperse currents with varying mass fractions of coarse and fine particles yields good agreement for all cases except those where the current consists almost exclusively of fine particles. For polydisperse currents over a two-dimensional bottom topography, significant discrepancies are observed. Possible reasons are discussed, including erosion and bed load transport. Finally, we investigate the influence of a three-dimensional Gaussian bump on the deposit pattern of a bidisperse current. [Copyright &y& Elsevier]

Abstract: Humans are increasingly altering the Earth''s surface, and affecting processes that shape and reshape landscapes. In many cases, humans are reacting to landscape-change processes that represent natural hazards. Thus, the landscape is reacting to humans who are reacting to the landscape. When the timescales for landscape change are comparable to those of human dynamics, human and ‘natural’ components of developed environments are dynamically coupled—necessitating coupling models of human and physical/biological processes to study either environmental change or human responses. Here we focus on a case study coupling models of coastal economics and physical coastline change. In this modeling, coastline change results from patterns of wave-driven sediment transport and sea-level rise, and shoreline stabilization decisions are based on the benefits of wide beaches (capitalized into property values) balanced against the costs of stabilization. This interdisciplinary modeling highlights points that may apply to other coupled human/natural systems. First, climate change, by accelerating the rates of landscape change, tends to strengthen the coupling with human dynamics. In our case study, both increasing sea-level-rise rates and changing storm patterns tend to increase shoreline change rates, which can induce more vigorous shoreline stabilization efforts. However, property values can fall dramatically as erosion rates and stabilization costs rise, which can also lead to the abandonment of expensive stabilization methods as shoreline change rates increase. Second, socio-economic change can also strengthen the human/landscape coupling. Changing costs of shoreline stabilization can alter stabilization decisions, which in turn alters patterns of coastline change. The coupled modeling illuminates the long-range effects of localized shoreline stabilization efforts; communities arrayed along a coastline are unwittingly affecting each other''s erosion rates, and therefore each other''s economies. Our coupled modeling experiments show that spatial distributions of property values and erosion rates can jointly affect economic outcomes, resource allocation between communities, and patterns of shoreline change. These findings raise questions about coastal management strategies, and efficient and equitable allocation of scarce resources among coastal communities. [Copyright &y& Elsevier]

Abstract: Indian River Inlet is located at roughly the mid-point of the Atlantic coast of Delaware and connects the ocean to two Delaware inland bays. Jetties constructed in 1940 have maintained the inlet for navigation purposes but have also acted as a barrier to net northerly alongshore sediment transport causing downdrift erosion. A mobile, land-based bypassing system was initiated in 1990 in an effort to counteract this erosion. Beach profile data from 1985 (pre-bypassing) until 2008 are used to investigate the effect of the sand bypassing system on beaches adjacent to the inlet. The downdrift beach experienced horizontal shoreline erosion between 10 and 60m during the pre-bypassing period but accreted 10–20m during the bypassing period. The mean shoreline location on the updrift beach during bypassing is 10–20m landward (erosion) of its position during the pre-bypassing period. Empirical orthogonal function (EOF) amplitudes from analyses performed on mean-removed elevation surfaces during the periods of highest bypassed volume (average of 83% of design rate) showed that the influence of the bypassing system on the downdrift beach extends to about 1500m of the inlet. An EOF analysis showed that different morphologic responses were evident following the initiation of bypass operations. Temporal variations of shoreline and beach morphology were correlated to the temporal variations in bypassing rates on the downdrift beach only. The downdrift beach response was greatest near the inlet for larger bypassing volumes. Correlation in these instances occurred with a roughly 1-year time lag suggesting that the beach quickly redistributes the bypassed sand. EOF amplitude and shoreline response are weakly correlated to bypassed volumes when the system bypassed smaller volumes (average of 56% of design rate) of sand suggesting that there is a minimum bypassing rate, regardless of yearly variability, below which the effect on the downdrift beach is obscured. [Copyright &y& Elsevier]

Abstract: This paper uses a multifaceted remote sensing and morphometric approach to investigate if the surface of subcatchments in the Parana Valles area of Mars (20–30°S, 0–20°W) is reflective of hydrology and sediment transport by water. Using digital elevation model (DEM) data obtained from the Mars Orbiter Laser Altimeter (MOLA), three nested subcatchments were examined using a suite of terrestrial geomorphic and hydrologic statistics to determine if their shape and form lies within the known range of fluvial catchment properties on Earth. Further, an examination of statistical accuracy via an innovative pixel-by-pixel solution of two statistics established that despite mineralogical homogeneity confirmed by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) spectral survey, erosion processes were likely to be variable across the study site. The DEM-based methods outlined here can be employed at other sites to investigate geomorphic properties and attributes of the Martian surface. [Copyright &y& Elsevier]

Abstract: The majority of subaqueous sediment on Earth consists of mixtures of cohesive clay and cohesionless sand and silt, but the role of cohesion on the development and stability of sedimentary bedforms is poorly understood. The results of new laboratory flume experiments on bedform development in cohesive, mixed sand–mud beds are compared with the results of previous experiments in which cohesive forces in high concentration clay flows dominated bedform development. Even though both series of mixed sand–mud experiments were conducted at similar flow velocities, the textural and structural properties of the bedforms were sufficiently different to permit the designation of key criteria for identifying bedform generation under cohesive flows against bedform generation on cohesive substrates. These criteria are essential for improving bedform size predictions in sediment transport modelling in modern sedimentary environments and for the reconstruction of depositional processes in the geological record. The current ripples developing on the cohesive, mixed sand–mud beds, with bed mud fractions of up to 18%, were significantly smaller than equivalent bedforms in noncohesive sand. Moreover, the bedform height showed a stronger inversely proportional relationship with initial bed mud fraction than the bedform wavelength. This is in contrast with the bedforms developing under the cohesive clay flows, which tend to increase in size with increasing suspended clay concentration until the flow turbulence is fully suppressed. Selective removal of clay from the mixed beds, i.e., clay winnowing, was found to be an important process, with 82–100% clay entrained into suspension after 2h of bedform development. This winnowing process led to the development of a sand-rich armouring layer. This armouring layer is inferred to have protected the underlying mixed sand–mud from prolonged erosion, and in conjunction with strong cohesive forces in the bed may have caused the smaller size of the bedforms. Winnowing was less efficient for the bedforms developing under the cohesive clay flows, where bedforms consisting of muddy sand were more characteristic. The winnowed sand was also found to heal irregularly scoured topography, thus reestablishing classic quasitriangular bedform shapes. In cohesive flows, the bedforms had more variable shapes, and the healing process was confined to lower transitional plug flows in which strong turbulence is only present close to the sediment bed. Furthermore, the bedforms on the cohesive beds tended to form angle-of-repose cross lamination, whereas low angle cross lamination was more common in bedforms under cohesive flows. In general terms, erosional bedforms prevail when cohesive forces in the bed dominate bedform dynamics, whereas depositional bedforms prevail when cohesive forces in the flow dominate bedform dynamics. Empirical relationships between the proportion of cohesive mud in the mixed sand–mud bed and the development rate and size of the bedforms are defined for future use in field and laboratory studies. [Copyright &y& Elsevier]

Abstract: This laboratory study describes the sediment patterns formed in a sand bed around circular patches of rigid vertical cylinders, representing a patch of reedy emergent vegetation. The patch diameter was much smaller than the channel width. Two patch densities (solid volume fraction 3% and 10%) and two patch diameters (22 and 10cm) were considered. For flows above the threshold of sediment motion, patterns of sediment erosion and deposition were observed around and within the patch. Scouring within the patch was positively correlated with turbulent kinetic energy in the patch. For sparse patches, sediment scoured from within the patch was mostly deposited within one patch diameter downstream of the patch. For dense patches, which experience greater flow diversion, sediment scoured from the patch was carried farther downstream before deposition along the patch centerline. Differences between the sparse and dense patch patterns of deposition are explained in the context of flow diversion and wake structure, which are related to a nondimensional flow blockage parameter. While sediment was redistributed near the patch, observations suggest that net deposition was not recorded at the reach scale. [Copyright &y& Elsevier]

Abstract: A new grid-based model of nutrient dynamics and transport process has been developed within a distributed hydrological modelling framework and integrated with river network module. The key aspect of this development is a process based description of nutrient generation process on the land surface and its related nutrient release with hydrologic runoff and soil erosion. Whereas the conventional modelling uses the event mean concentration method for nutrient dynamics modelling and estimates nutrient loads from catchments to the rivers this study has introduced an export function based release related with flow capacity. The river module solves the dynamic equation for transport and chemical reaction. The model output is available in high spatial and temporal resolution, which was tested and verified applying in two catchment areas from different hydro-climatic backgrounds. The model was able to simulate short term high intensity flood events as well as long term seasonal patterns. The simulated results for most of the nutrient parameters are within acceptable range as reflected by measures of statistical indices and visual interpretation. For example, the R 2 values for different nutrient levels in the Saru River, Japan are within the range of 0.83–0.99 and 0.66–0.87 for calibration and validation, respectively. Similarly, the relative root mean square error (RRMSE) values for different nutrient levels in the Saru River range between 0.06–0.22 and 0.06–0.26 for calibration and validations, respectively. The maximum load of nutrients in each grid was extracted from time series output, analyzed further and presented in two dimensional maps, which showcase the usefulness of the model in decision making process for management of land and maintenance of the in-stream water quality. [Copyright &y& Elsevier]

Abstract: The paper introduces a 2D shallow water model based on a two-phase formulation for the analysis of fast geomorphic transients occurring in the context of river morphodynamics. Mass and momentum conservation principles are separately imposed for both phases. The model naturally accounts for non-equilibrium solid transport, since neither instantaneous adaptation hypothesis nor any lag equation is employed to represent sediment dynamics. The hyperbolic character of the proposed model is shown to be preserved independently on the flow conditions. Results from numerical simulations of both 1D and 2D test-cases are compared with literature experimental data and with available numerical solutions. [Copyright &y& Elsevier]

Abstract: Analysis of typhoon- and earthquake-triggered landsliding and fluvial response in the Tachia River, central Taiwan, documents highly episodic sediment supply over decade to century timescales. Landslide data from the Chi-Chi earthquake (1999) and subsequent typhoons (2001, 2004, and 2005) quantify the sediment supply from these events. Fluvial response was investigated by decadal-scale and century-scale longitudinal river profile data spanning 1904 to 2008 and by sediment delivery recorded in suspended sediment load and reservoir sedimentation data. Our results show that the different time periods of satellite images and aerial photographs used in previous studies make it difficult to unambiguously identify the causes of landslides previously attributed by some studies to the effects of the Chi-Chi earthquake rather than subsequent high intensity precipitation. In response to significant variability in sediment delivery from hillslopes, century-scale profile variation data indicate substantial bed surface elevation change of 2.6±6.7m, and decade-scale bed surface elevation change of 1.1±3.3m. Since 1993, the downstream reaches incised in response to bedload sediment trapping by reservoirs while headwater reaches aggraded in response to increased sediment delivery from uplands. A tremendous increase in reservoir sedimentation after 2000 likely reflects the effects of the highest decade-average daily rainfall since 1900. Suspended sediment load data indicate a post Chi-Chi earthquake increase in sediment concentration in low-flow events but do not exhibit the clear influence on sediment yields at higher flows as (e.g., typhoons) reported by others for fluvial response in the epicentral region. [Copyright &y& Elsevier]