Sediment Transport Function Research Articles

Analyzing sedimentation patterns in the Naumure Multipurpose Project (NMP) reservoir using 1D HEC-RAS modeling

Naumure Multipurpose Project (NMP) featuring a 169 m high Concrete Face Rock Filled Dam (CFRD) is the proposed reservoir project in the West Rapti River with an installed capacity of 218.34 MW. Most of the rivers in Nepal carry significant sediment loads that will consequently catalyze reservoir sedimentation. This phenomenon prevails as the primary factor in reducing reservoirs useful life, making ineffective for both flood control and hydroelectricity generation. Ultimately, such process of sedimentation has adverse impacts on projects economic feasibility and long-term sustainability. Therefore, the objective of this research was to examine the expected sediment deposition pattern in the NMP reservoir throughout its operational period by employing 1D HEC-RAS model to simulate the sedimentation process. The model was simulated for 10, 20, 30, 40 and 50 years. Yang’s equation as a sediment transport function, Active layer as a bed sorting method and Toffaleti as a fall velocity method were best suited for the river reach. The delta deposition was formed between 11 km and 22 km upstream of the dam region in the Jhimruk river, with the sediment deposition depth reaching peaks of about 23 m, 38 m, 39 m, 41 m and 49 m in 10, 20, 30, 40 and 50 years, respectively. Similarly, the delta deposition was formed between 13 km and 33 km upstream of dam region in the Madi river, with the sediment deposition depth reaching peaks of about 47 m, 62 m, 60 m, 68 m and 75 m in 10, 20, 30, 40 and 50 years respectively. Headcutting of delta deposition occurred between 20 and 30 year due to high flood during low stage of reservoir. Furthermore, the study revealed that about 6.22%, 11.61%, 15.94%, 22.96% and 25.65% of the storage capacity of NMP reservoir will be depleted in 10, 20, 30, 40 and 50 years respectively.

Temporal variation of braided intensity and morphodynamic changes in a regulated braided river using 2D modeling and satellite images

AbstractThe river morphology of a braided‐type river is rather complex. High sediment transport rates and frequently changing discharges are the cause of dynamic planform evolution. Over the past few decades, scientific attention has been directed toward understanding the coexistence of alternating bars and the consequent emergence of confluences and divergences, all of which interact intricately with the process of bank erosion. It is still rather challenging to estimate or predict the total sediment transport rate in this type of river, especially by considering various hydrologic data and climate effects. This study is focused on the reach of the Devoll River in Albania, located upstream of the Banja dam. Understanding the morphodynamics of this river reach holds significance due to the expanding delta upstream of the dam reservoir. The objectives of the two‐dimensional depth‐averaged approach of the present study are to investigate the temporal variation of braided intensity of Devoll River and the effect of using a discharge hydrograph from hydrologic data compared to the regulated one from the upstream dam on the morphodynamics and sediment transport of the river. After evaluating various parameters such as 11 different sediment transport functions, the best results were reached for a cell size of 5 × 5 m2, Manning roughness coefficient of 0.03, Meyer‐Peter and Müller's sediment function, Hayashi et al. (1980) hiding function, and Van Rijn bed roughness predictor in this study. In addition, the results of comparing satellite images and modeling the river from 2019 to 2023 show that the braided index decreased, and this can be due to the fact that the real scenario of the river has a regulated discharge compared to the non‐regulated discharge from hydrologic data, in the mentioned period.

Sediment transport modelling upstream of Al Kufa Barrage

Abstract This study estimated the amount of bed sediment load upstream of Kufa Barrage mainly depending on the hydrodynamic conditions, sediment concentration, and hydraulic parameters. Ten cross-sections approximately over 2 km in length in front of the barrage were selected. Velocities and suspended sediment concentrations at 0.2, 0.6, and 0.8 of the water depth at each section were recorded using an ADCP device. A depth-integrated sampling was utilized to examine the collected data from 6th January to 15th October 2022. It was noted that the effective depth-to-width computation methods and the Toffaleti sediment transport function with the Van Rijn fall velocity were the most compatible and appropriate approaches for determining the sediment transport potential in the selected reach. It was also noted that such techniques were better than the previous formulae to predict the total sediment load. The results revealed excellent agreement between the mean sediment discharge obtained using HEC-RAS 6.2, equal to 6.214 kg/s, and the mean sediment discharge obtained from the field measurements, equivalent to 7.142 kg/s.

Angkutan Sedimen Total Saluran Pembawa Embung Rawasari menggunakan Metode Empiris dan Software HEC-RAS 6.0

The need for water will continue to increase, while the availability of water is limited; therefore, the provision of water must be pursued both by the government and independently. Rawasari Reservoir is one of the reservoirs in Tarakan City with a relatively stable volume and an effective storage capacity of 112,982 m3. The water source of Rawasari Reservoir comes from a channel that is a tributary experiencing sedimentation due to the sedimentation process. Based on this, the research team was interested in calculating sediment transport in the conveyance channel of Rawasari Reservoir using both empirical methods and the HEC-RAS 6.0 software. The methods used in this research are empirical using the Engelund Hansen and Laursen equations, as well as the use of HEC-RAS 6.0 software. Based on the analysis results, the sediment transport rate in the conveyance channel of Rawasari Reservoir calculated using the empirical method at STA 0+025 is 1,6427 x 10-9 ton/s for the Engelund Hansen method and 2,9898 x 10-9 ton/s for the Laursen method. The simulation of sediment transport in the bed of the conveyance channel of Rawasari Reservoir using the HEC-RAS 6.0 sediment transport model at STA 0+025 is 4,61x10-5 ton/s with the Engelund Hansen sediment transport function and 0,000306 ton/s using the Laursen sediment transport function.

The use of temporary, permeable structures in the lower burdekin river: A novel approach to river-level management

A review of in-channel structures finds a wide range of purposes, including enhancement of the storage capacity of rivers to improve water supply reliability and/or flood protection, and various other hydro-ecological, water quality, geomechanical and sediment transport functions. The installation of in-channel structures is typically intended to be permanent, or at least semi-permanent. The purpose of this note is to document the novel use of temporary in-channel structures in the lower reaches of the Burdekin River, within the Australian dry tropics. Their application reduces freshwater discharge to the sea during low-flow periods thereby enhancing the sustainability of irrigated agriculture within the Lower Burdekin Delta. Temporary structures are constructed in the Burdekin River to enhance the reliability of pumping stations by raising the river level locally and preventing sea water from reaching extraction points. The structures are designed to restrict river flow only partially during low-flow periods and to wash away during high-flow events, which provides several benefits, including the passage of riverine fauna and reduced river siltation. The long-term utilisation (1950s to present) of temporary structures in the Burdekin River is testament to their successful implementation, which may offer benefits over permanent structures for other dry-tropical regions.

Characteristics of fluid mud in the Yangtze Estuary: Storm, tide, and slope-triggered sediment dynamics and effects

Fluid mud is widely found in estuarine and coastal areas and significantly affects sediment transport, navigational safety, and ecological functions. The formation mechanisms of fluid mud are not yet fully understood because of their complex dynamics, including the effects of riverine discharge, tides, storms, and gravity-driven flows. In this study, the in situ density of 18 fluid mud events was measured along the deep navigation channel (DNC) of the Yangtze Estuary from 2010 to 2016, along with hydrodynamic factors such as riverine discharge, wind, waves, tidal stratification of salinity and suspended sediments, and channel slope. Our results indicate that the scale of storm-triggered fluid mud events in the DNC was 10–60 km long and 0.5–4 m thick, and tidal residual flow circulation and salinity stratification co-formed fluid mud and determined its structure along the DNC. In addition, the coupled stratification induced by the suspended sediment concentration and salinity affected the thickness of fluid mud, and the strengthened stratification induced by the decreasing tide current affected the thickness of high-density fluid mud. Furthermore, gravity-driven flow induced by the steep slope on both channel banks enhanced the accumulation of fluid mud in the DNC. Finally, fluid mud accounted for 20% of the annual silted sediment in the DNC, and the upper low-yield-stress layer of fluid mud (density <1250 kg/m3) could be utilized as the potential nautical depth during fluid mud events, accounting for 20–75% of the entire thickness of the fluid mud. The results of this study can improve the understanding of fluid mud processes and mechanisms and promote cost-effective dredging activities, particularly in muddy tide-dominated estuaries.

Hydrodynamic Model-Based Evaluation of Sediment Transport Capacity for the Makhool-Samarra Reach of Tigris River

This paper implemented an HEC-RAS-based steady two-dimensional hydrodynamic model to evaluate the hydraulic characteristics and Sediment Transport Capacity (STC) of the Makhool-Samarra Reach of the Tigris River, where this part is not already investigated. This model was prepared with the aid of topographical surveys, hydraulic measurements, and laboratory tests, as well as recorded data. The main findings show that the flow velocities within most of the studied reach are considered high compared to the local and worldwide flow velocity ranges in natural rivers. Also, the Toffaleti sediment transport function with the Van Rijn fall velocity and the effective depth-to-width computation methods are the most compatible and suitable methods for computing the Sediment Transport Potential (STP) in the ‎studied reach. With the maximum flow, the computed STP was less than the average (5.7×106 tons/day) in 45% of the reach length, where the maximum STP is 8.7×106 tons/day. However, with the minimum flow, the STP intermittently fluctuates below the average (0.2×106 tons/day) in 48% of the reach length, where the minimum STP is 0.14×106 tons/day. Generally, these STPs are little more than the Tigris River in Mosul and much higher than that in Baghdad. Also, these STPs are considered high on a global scale, especially during high flow. Medium gravel is the larger grain gradation class that can be transported. It constitutes less than 0.00005 % of the STP. Furthermore, the STC computations clearly show that the suspended sediment is the dominant part of the STC and the bed material constitutes less than 0.002% of the STC of the total load. However, most of the STC ‎concerns the clay and very fine silt.

A Coupled Hydrodynamic-Equilibrium Type Beach Profile Evolution Model

An equilibrium beach profile model is developed and coupled with a parametric hydrodynamic model to provide feedback between the evolving morphology and the hydrodynamics. The model is compared to laboratory beach profiles evolving toward equilibrium conditions under constant forcing. The equilibrium model follows the classical approach but uses the bulk sediment transport as the governing model parameter. This approach is coupled with empirically derived and normalised sediment transport functions and a parametric surf zone wave transformation model. The dissipation predicted by the surf zone model controls the cross-shore position of the maxima in the sediment transport functions and hence the cross-shore evolution of the beach profile. Realistic beach profile shapes are generated for both erosive (barred) and accretive (bermed) beach profiles, and predictions of bar and berm position are satisfactory. With more complex normalised sediment transport functions, the model can be applied to conditions with a cyclical wave climate. However, the model concept is better associated with erosive wave conditions and further work is required to improve the link between the modelled dissipation and local transport for accretive conditions.

Sediment transport functions in HEC-RAS 4.0 and their evaluation using data from sediment flushing of Wlingi reservoir - Indonesia

This paper presents a study carried out to assess the accuracy of several sediment transport functions commonly applied in HEC-RAS 4.0 against data from the sediment flushing of Wlingi reservoir in 2016. Another aim of this assessment is to evaluate the viability of selected transport equations to simulate riverbed changes during the sediment-flushing event. Thus, the best scenario of sediment flushing could be determined according to their efficiencies. The overall accuracy of the transport function indicated by RMSE values in descending order were those of Laursen-Copeland, Ackers and White, Meyer-Peter and Müller, and Wilcock formulas, when applied to the observed data. The study also indicated that Laursen-Copeland formula had parameters that were commonly well-characterized by the riverbed of Wlingi reservoir. Further, it was suitable to be utilised to assess the achievement of sediment flushing in Wlingi reservoir, while others seem less satisfactory.

Assessment of Sediment Transport Functions with the Modified SWAT-Twn Model for a Taiwanese Small Mountainous Watershed

In Taiwan, the steep landscape and highly vulnerable geology make it difficult to predict soil erosion and sediment transportation via variable transport conditions. In this study, we integrated the Taiwan universal soil loss equation (TUSLE) and slope stability conditions in the soil and water assessment tool (SWAT) as the SWAT-Twn model to improve sediment simulation and assess the sediment transport functions in the Chenyulan watershed, a small mountainous catchment. The results showed that the simulation of streamflow was satisfactory for calibration and validation. Before model calibration and validation for sediment, SWAT-Twn with default sediment transport method performed better in sediment simulation than the official SWAT model (version 664). The SWAT-Twn model coupled with the simplified Bagnold equation could estimate sediment export more accurately and significantly reduce the overestimated sediment yield by 65.7%, especially in highly steep areas. Furthermore, five different sediment transport methods (simplified Bagnold equation with/without routing by particle size, Kodoatie equation, Molinas and Wu equation, and Yang sand and gravel equation) were evaluated. It is suggested that modelers who conduct sediment studies in the mountainous watersheds with extreme rainfall conditions should adjust the modified universal soil loss equation (MUSLE) factors and carefully evaluate the sediment transportation equations in SWAT.

Numerical and Experimental Studies in Prediction of Bed Levels of Aggrading Channels

A semi-coupled 1D numerical model is presented to compute transient bed and water levels of aggrading channels due to the overloading of sediments. The numerical model solves mass and momentum equations (i.e. de Saint–Venant equations) for water and continuity equations for sediments simultaneously, using explicit finite difference scheme while considering upstream and downstream boundary conditions in the channel. Series of experimental studies are reported for measurements of bed and water levels in an aggrading channel due to the overloading of uniform sediments, in a flume installed at the Advanced Hydraulics Laboratory of SVNIT. The performance of bed level variation models, with different sediment transport functions, has been validated using the laboratory measurements. The performance of the numerical model is dependent on sediment transport functions. In addition, the performance of the proposed numerical model has been verified with existing numerical models on prediction of bed level variations. The proposed numerical model with recommended sediment transport function has been found to perform better than the existing numerical models on bed level variations of uniform sediment beds.

Prediction of bed level variations in nonuniform sediment bed channel

In the present study, a numerical model, based on one-dimensional de Saint-Venant equations along with sediment continuity equation, is developed for prediction of bed levels in non-cohesive sediments in aggrading alluvial channels. One-dimensional, unsteady flow equations and sediment continuity equations are solved using ‘shock-capturing’, second order accurate, explicit MacCormack finite difference scheme while considering upstream and downstream boundary conditions in the channel. Series of experimental investigations have been undertaken for measurements of bed and water levels in an aggrading channel due to overloading of nonuniform sediments, extracted from the bed of Tapi River at Surat City, in a flume installed in Advanced Hydraulics Laboratory of SVNIT, Surat, India. A satisfactory coupling between the water flow and sediment flow has been achieved. The sediment continuity equation is used for the each size class to compute the volume of each size class after each time step at any computational node in the computational grid. The fractional bed and suspended load transport capacities for different size fractions have been computed using fractional transport laws for nonuniform sediments. The active bed layer concept has been implemented in finite difference scheme to consider the interaction and exchange of sediment and water flow near the mixing layer. The performance of developed numerical model has been satisfactorily verified with independent experimental data of nonuniform sediment bed. Also, consideration of sediment nonuniformity in computation of bed level variation has been demonstrated by comparing the results based on sediment transport functions of uniform and nonuniform sediments.

Characteristics of suspended particulate matter in a typical slow-moving river of northern China: Insight into its structure and motion behavior

To investigate the characteristics of suspended particulate matter (SPM) in rivers of northern China, SPM was collected from 20 sampling sites within the severely polluted slow-moving Ziya River Mainstream (ZRM) and from 20 sampling sites within the less-polluted fast-moving Luanhe River (LR) between October and November of 2016. Physical and chemical attributes of river water from the ZRM and LR were measured; the microstructure, specific surface area and particle size of the SPM were also determined. The SPM had thicker organic coated layers on inorganic particles within the ZRM, compared with the LR, indicating strong interaction of the SPM with the water column. Along the ZRM length, these organic coated layers evolved, first plugging particle pores and then increasing in volume, causing the specific surface area to decrease at first and then increase. The presence of organic coated layers on inorganic particles greatly changed their particle size, density and inducing changes in their motion behavior. Such changes in SPM microstructure were most apparent in the slow-moving polluted ZRM. Given that SPM can adsorb contaminants, such as phosphorus and heavy metals, onto its surfaces and transport them downstream, these changes could have a profound impact on both sediment transport and river ecosystem function. Our results suggest we need to reevaluate our previous river management measures for slow-moving polluted rivers.

Analytic Theory of Equilibrium Fluvial Landscapes: The Integration of Hillslopes and Channels

A physically based theory for equilibrium fluvial landscapes undergoing transport‐limited or detachment‐limited erosion is derived from equations for water flow, erosion, and hillslope stability. A scaling analysis of the equations identifies submodels for overland and channelized flows. The channel‐slope boundary (CSB) defines the interface between the two flow environments, marking the bifurcation of stable overland flows into unstable sheet flows and stable channel flows. The characteristics of CSBs are derived from an equilibrium condition of the hillslope submodel and stability conditions derived from the time‐dependent model. Equilibrium hillslopes are characterized by proportional flows of water and sediment, uniformly constant and maximum values of water flow (qc) and slope occurring on the CSB, and the minimization of a Lagrangian function of energy. Equilibrium solutions are readily derived for laminar overland flows. Power law sediment transport functions for channel flow lead to stable self‐similar solutions for channel segments characterized by realistic hydraulic geometries. Uniform equilibrium inflows qc result in straight segments of channel that are combinable into networks satisfying admissibility constraints. The aggregate length of CSB upstream of any network point determines total channel discharge and hence channel slope and elevation, providing boundary conditions that determine hillslope elevations. Large equilibrium landmasses with rainfall rate R have relatively uniform drainage densities . Changes to channel networks induced by environmental fluctuations may occur at any network location because maximum, neutrally stable overland flows qc occur on the CSB. Stable equilibrium surfaces are conjectured to correspond to local minima of the Lagrangian over the space of admissible networks.

Reconstruction of sediment-transport pathways on a modern microtidal coast by a new grain-size trend analysis method

A new method for granulometric-parameter-based reconstruction of sediment-transport pathways is proposed and is termed P-GSTA (grain-size trend analysis using principal component analysis) herein. The main advantage of this method is its applicability to depositional environments involving mixed transport processes, for instance, fluvial, tidal, and wave-influenced environments. In the P-GSTA method, a linear function with all significant granulometric parameters that are summed with different weighting factors was used to infer sediment-transport direction (sediment flux pattern); the previous grain-size trend analysis (GSTA) methods considered only three parameters (mean grain size, sorting, and skewness) with equal weighting. This study chose six parameters (namely, median grain size, coefficient of variation, skewness, kurtosis, and mud and gravel log-ratios) for calculation. First, the zero values of mud and gravel fractions are replaced, and their log-ratios are defined. Then, all values are standardized. Thereafter, principal component analysis (PCA) is conducted to determine the weighting factor of each granulometric parameter. Each principal component is then interpreted, and the function best representing a sediment flux pattern is chosen from these components. Trend vectors are calculated, solely on the basis of a map interpolated from the scores of the chosen principal component, as the two-dimensional gradient of this value. The P-GSTA method proposed in this study was applied to a modern microtidal coast (tidal sand flat along the Kushida River Delta, central Japan). Sediment-transport pathways reconstructed by this method were consistent with observed sediment-transport patterns determined by field experiments using tracer sediments and geomorphologic observation; the results of the previous GSTA method were inconsistent with the observations. The proposed method also revealed additional minor depositional processes on the sand flat, namely, the deposition of fluvial-channel lags and muddy particles. Thus, this study demonstrates that the proposed P-GSTA method is a potentially powerful tool to reconstruct sediment-transport patterns even under mixed transport processes, where the estimation of the sediment-transport function is difficult.

Numerical modeling of the Sakuma Dam reservoir sedimentation

The present study attempts to predict the reservoir sedimentation in 32 km region of the Tenryu River between the Hiraoka and Sakuma Dams in Japan. For numerical simulations of the reservoir sedimentation, the one-dimensional model of the Hydrologic Engineering Centre-River Analysis System (HEC-RAS) is used together with the inclusion of channel geometry, bed gradation curve, Exner-5 bed sorting mechanisms, fall velocity of the particle, and flow and sediment boundary conditions pertaining to modeling region. The modeling region of the Tenryu River is divided into 48 river stations with 47 reaches in the numerical simulations. The numerical model is calibrated using the available data for 48 years from 1957 to 2004. The formulae of sediment transport function, Manning’s roughness coefficient, computational increment and fall velocity have been identified for getting the best estimation of the Sakuma Dam reservoir sedimentation. Combination of obtained sensitive parameters and erodible limits of 2 m gave the best comparison with the measured bed profile. The computed results follow the trend of measured data with a small underestimation. Although Manning’s roughness coefficient has an effect on the sedimentation, no direct relation is found between the Manning’s roughness coefficient and reservoir sedimentation. It is found that the temperature of water has no effect on the reservoir sedimentation.

A total load approach to predict bed load transport of Indian alluvial river

Bed load data are scarcely measured continuously for Indian rivers. In the absence of measured bed load data, the present study tests bed load computed using selected bed load sediment transport functions. The computed bed load is compared with widely accepted thumb rule estimation of the bed load, i.e. the Maddock’s approach. To check the suitability of these bed load equations for Indian river (Purna River), the computed bed load (BLc) has been added to observed suspended load and total load of the Purna River is derived. On other hand, the total load for the Purna River is worked out using Yang’s (1973) unit stream power approach for total load prediction. The total load computed (TLc) for the Purna river is then compared with the total load predicted (TLp) using Yang’s approach. It is observed that best prediction in total load transport is obtained when bed load is computed as 10% of observed suspended load. A similar performance is obtained when bed load is computed using Recking’s bed load function.

Assessment of Optional Sediment Transport Functions via the Complex Watershed Simulation Model SWAT

The Soil and Water Assessment Tool 2012 (SWAT2012) offers four sediment routing methods as optional alternatives to the default simplified Bagnold method. Previous studies compared only one of these alternative sediment routing methods with the default method. The proposed study evaluated the impacts of all four alternative sediment transport methods on sediment predictions: the modified Bagnold equation, the Kodoatie equation, the Molinas and Wu equation, and the Yang equation. The Arroyo Colorado Watershed, Texas, USA, was first calibrated for daily flow. The sediment parameters were then calibrated to monthly sediment loads, using each of the four sediment routing equations. An automatic calibration tool—Integrated Parameter Estimation and Uncertainty Analysis Tool (IPEAT)—was used to fit model parameters. The four sediment routing equations yielded substantially different sediment sources and sinks. The Yang equation performed best, followed by Kodoatie, Bagnold, and Molinas and Wu equations, according to greater model goodness-of-fit (represented by higher Nash–Sutcliffe Efficiency coefficient and percent bias closer to 0) as well as lower model uncertainty (represented by inclusion of observed data within 95% confidence interval). Since the default method (Bagnold) does not guarantee the best results, modelers should carefully evaluate the selection of alternative methods before conducting relevant studies or engineering projects.

Three-dimensional airflow and sediment transport patterns over barchan dunes

Airflow dynamics and potential sediment transport were measured and modelled across various barchan dune topographies and incident wind conditions. Modification of near surface flow was recorded simultaneously in three dimensions (3D) using dense arrays of high-resolution 3D ultrasonic anemometers. In situ measurements provided rigorous validation and calibration for computational fluid dynamics (CFD) modelling. Measured and modelled results show good agreement between flow velocity, directionality, and turbulence intensity. Modelling of characteristic airflow conditions and surface shear stress beyond the instrument locations, elucidated airflow dynamics across the entire landform surface at an unprecedented level of detail. Emergent turbulent airflow patterns were identified in the form of two counter-rotating vortices that converge at the dune centreline downwind of the dune crest. Integrating a sediment transport function with CFD surface airflow allows for the spatial mapping of flux patterns across the entirety of the dune and interdune surface. On the stoss slope and laterally along the outer barchan arms, there is strong potential sediment flux in response to increased streamwise stress. In lee-side locations, sediment transport remains at ‘above threshold’ conditions and is redirected in response to complex turbulent vortices identified in the overlying wake zone. The precision of the models allows for the identification of complex flow perturbations and associated surface stresses that prove difficult to measure in the field. CFD in combination with a sediment transport function is demonstrated to be a useful tool in investigating morphodynamics of mobile dune systems.

Simulating bed evolution following the Barlin Dam (Taiwan, China) failure with implications for sediment dynamics modeling of dam removal

The failure of the Barlin Dam in Taiwan, China offers an important case study for evaluating concepts in modeling the rapid erosion and channel recovery following intentional and unplanned dam removals. We present a modeling effort that applied a 1D and quasi-2D uncoupled hydraulics and sediment model (NETSTARS) to evaluate how discretization and parameterization influence thefitofbed elevationpredictions to observations following dam failure. Our analysis evaluated the model sensitivity to sediment transport function, active layer thickness, and number of stream tubes used to define the cross-section. Results indicate that a) the model is more sensitive to active layer thickness and sediment transport function than to the number of stream tubes, b) development of dam removal models are likely to benefit from varying the active layer thickness in time, and c) increased lateral discretization does not appear to improve model fit in the steep and rapidly changing river environment at our site. We conclude with discussion on differences between, identifying the need for, and general use of 1D, quasi-2D, and fully 2D models in dam removal and failure analysis.