Property:CSDMS meeting abstract
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Extreme drought events are becoming more frequent and severe. For example, since the flash drought of 2012 that ravaged the central United States, 2019 was the only year that has not experienced a billion dollar drought disaster. Examining how vegetation-atmosphere interactions change during extreme drought events can improve our understanding of how resilient different plants are at dealing with water stress during drought. We couple a prognostic phenology routine to a 1-D version of the Duke Coupled surface-subsurface Hydrology Model with dynamic vegetation (DCHM-V) to simultaneously simulate changes in plant life stage with water, energy, and carbon fluxes. The predictive phenology model simulates daily changes in canopy greenness and density based on the current meteorological conditions within the DCHM-V. We run the DCHM-V at a 4 km spatial resolution and hourly time step for pixels encompassing three AmeriFlux sites in the Midwestern United States. Modeling phenological changes and resulting land-atmosphere interactions allows us to investigate physical processes governing vegetation water use strategies in response to flash drought. Results show that vegetation under average water-use scenarios experience smaller reductions in growth as compared to isohydric or anisohydric water-use strategies. Transpiration dominates evapotranspiration with ample precipitation but is nearly cut in half during extreme drought resulting in reduced plant water use efficiency. These findings demonstrate the importance of incorporating dynamic phenological when investigating how vegetation modulates water, energy, and carbon under different water stress conditions, and have implications for improving predictions of drought impacts on the land surface. +
Features of landscape morphology including slope, curvature, and drainage dissection are important controls on runoff generation in upland landscapes, while over long timescales runoff plays an essential role in shaping these same features through surface erosion. Many hydrologists have speculated about the importance of this coevolution and its potential for generating hydrological insights; however, observational and computational limits have long prevented direct study of coupled hydro-geomorphic systems over long timescales. What kinds of hydrological features do landscapes exhibit when their runoff is `in-tune' with the form of the landscape? Here we answer this question using a new coupled hydro-geomorphic model that is sophisticated enough to capture saturated and unsaturated zone storage and water balance partitioning between surface flow, subsurface flow, and evapotranspiration, but efficient enough to drive a landscape evolution model over millions of years. We nondimensionalize the model to arrive at a minimal set of dimensionless numbers that provide insight into how hydrologic and geomorphic parameters together affect the ultimate state. Model results show a diverse array of behaviors observed in real watersheds, including the presence of variable source areas and nonperennial streams. We also found some results that were unique and surprising, such as non-dendritic drainage networks. We hope that these results will inspire hydrologists to consider the role that landscape history plays in the hydrological processes observed today and inspire geomorphologists to consider the role of more nuanced hydrological processes in long-term landscape evolution. +
Field-based observations and numerical models of strike-slip faults indicate that the regional footprint and preservation of the landscape response depends on fault slip rates, climatic conditions, and surface erosional activity. Arid desert environments, on one end of the climate spectrum, are especially sensitive to climate changes and tend to provide an excellent record of fault-slip histories and landscape modification in response to faulting. For example, the Salar Grande strike-slip fault slips at slow to moderate rates (~1 mm/yr) across the Atacama Desert of Chile and is characterized by long periods of hyper aridity with the absence of fluvial activity, but still preserves dextral offset geomarkers evidencing past humid periods and faulting. Conversely, wet environments are intensively affected by constant fluvial erosion and mass wasting. For example, in Aotearoa New Zealand, complex systems of parallel right-lateral faults in the Tararua Mountains, North Island, interact with each other with neighboring rivers flowing across and along fault branches that slip at different rates (< 1 mm/yr to > 10 mm/yr) and juxtapose different scale high-relief topography (shutter ridges). Inspired by the complexities of these real-world contrasting strike-slip fault settings, we create analog numerical simulations in Landlab to observe the role of climate variability, sediment, and the interaction between multiple structures affecting the topography. Model results are compared with field observations, focusing on channels, ridges, and mountain range scale observations. +
Field-based studies, remote sensing analyses, and model development inform our understanding of patterns and processes in incipient delta formation and continued progradation. Rarely, however, have the three approaches been used together to understand the entire progradation history of a real-world system. This may be largely due to the paucity of appropriate sites: an accessible location where a delta has been growing for just a few decades. One site that meets these criteria is Mamawi Creek delta, located within the larger Peace Athabasca Delta ecosystem in northeastern Alberta, Canada. Mamawi Creek delta began forming in 1982, just two years before the beginning of Landsat TM observations over boreal Canada. Due to strong scientific interest and human presence in the region, data on sediment, flow, water levels, and elevations have been collected for decades. Here, we use these available field data to create a site-specific morphodynamic model of Mamawi Creek Delta in Delft3D. Leveraging discoveries from previous modeling studies that have examined how inputs, such as percent of cohesive sediment and median grain size, affect resulting delta forms, we approach the inverse question to see how observed delta characteristics in the Landsat record can constrain model setup and inputs. By comparing annual model outputs against remotely sensed observations of true delta form over the last 40 years, we learn the limitations of our field data and consequences of model simplifications. We then iteratively use these comparisons to inform model parameter adjustments and changes to boundary conditions that enhance agreement between these two methods, ultimately producing a simulated delta that acceptably mimics observed progradation. +
First-order delta morphology is primarily governed by the dominant driver of sediment transport (river, waves, or tides), which dictates the overall sediment balance of the delta. Vegetation affects morphology through its influence on hydraulic roughness, introducing flow resistance, altering velocity distributions, and modulating sediment deposition. In turn, morphodynamic changes affect vegetation, creating a bio-geomorphic feedback-loop that results in a dynamic equilibrium, where the delta’s morphology and dynamic vegetation co-evolve over decadal timescales. This study examines how dynamic saltmarsh vegetation influences delta morphology in a river-dominated delta. We used Delft3D coupled with an ecomorphodynamic model to simulate the feedback-loop between dynamic vegetation and an idealized river-dominated delta, inspired by Wax Lake Delta, Louisiana. The ecomorphodynamic model simulates vegetation establishment, growth, and mortality resulting in dynamic variations of vegetation height and density that produce realistic hydraulic roughness distributions. Our findings demonstrate how vegetation-induced roughness variations can influence sediment redistribution and changes in bed elevation, affecting the morphology. This research highlights the importance of considering vegetation in morphodynamic studies, improving the understanding of delta systems. +
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Flash floods are among the most devastating natural hazards, which cause loss of life and severe economic damages. Modeling flash floods to provide warnings to the public to prevent/mitigate the impacts of this type of disaster is still challenging. A coupled model which consists of the currently used Hydrology Laboratory - Research Distributed Hydrologic Model (HL-RDHM) at NWS and a high resolution hydraulic model (BreZo) has been developed for flash flood modeling purposes. The model employs HL-RDHM as a rainfall-runoff generator in coarse resolution to produce surface runoff which will be zoned into point source hydrographs at the sub-catchment outlets. With point source input, BreZo simulates the spatial distributions of water depth and velocity of the flow in the river/channel and flood plain.
The model was utilized to investigate the historical flash flood event in the Upper Little Missouri River watershed, Arkansas. This event occurred on June 11th, 2010 and had killed 20 people and caused severe property damages. The catchment was divided into 55 sub-catchments based on Digital Elevation Model (DEM) at 10m resolution from USGS. From HL-RDHM surface runoff, 55 hydrographs can be derived, which then become 55 point sources as input in BreZo. The system was calibrated by tuning the roughness parameter in BreZo to best match the USGS discharge observation at the catchment outlet. The simulation results show the system performed very well not only for the total discharge at the catchment outlet (Nash-Sutcliffe efficiency = 0.91) but also the spatial distribution of the flash floods. +
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Flood hazards can increase or decrease as a result of changes in the frequency of high flows and changes in the geometry of river channels, through aggradation, incision, or widening. Across the US, Slater et al. (2015) found that a statistically significant majority of studied sites saw increases in the frequency of flooding over the past several decades. Notably, the magnitude of channel response and hydrologic non-stationarity varied between channels within a region. Here, we focus in on a single region, the Pacific Northwest, and ask 1) can the geomorphic characteristics of a basin explain historical changes in flood hazard? And, 2) how will flood risk change with climate change in relation to source-to-sink sediment dynamics? As a first step in understanding the sensitivity of different basins to future climate change, we look at historical records of both channel geometry change and discharge records at ~60 USGS gage sites across Washington state. We find substantial variation among the studied sites in the magnitude of channel change (quantified in terms of changes in the stage-discharge relationship) over the past 3 decades. Some channels have maintained a steady stage-discharge relationship over 30 years, while others change dramatically on an annual basis. Many, but not all, of these unstable channels drain basins with retreating alpine glaciers. Inspecting the discharge records, we find substantial variation as well, likely driven by the differences in hydrologic regime. In the future, we will use this understanding of historical channel sensitivity to inform our predictive models of both channel geometry change and non-stationarity in high flows. +
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Floodplain deposition maintains and builds up low-lying lands along rivers and in deltas. Floodplain aggradation processes and patterns determine how vulnerability of low-lying land changes over timescales of decades to hundreds of years. Over the longterm, floodplain deposition and channel migration determine the depositional architecture with impacts on groundwater and hydrocarbon reservoirs.
We build and enhanced a 3D floodplain architecture model, AquaTellUs. AquaTellUs uses a nested model approach; a 2D longitudinal profile, embedded as a dynamical flowpath in a 3D grid-based space. A main channel belt is modeled as a 2D longitudinal profile that responds dynamically to changes in discharge, sediment load and sea level. Sediment flux is described with a modified Exner equation by separate erosion and sedimentation components. Erosion flux along the main flowpath depends on river discharge and channel slope, and is independent of grain-size. Depositional flux along the channel path as well as in the lateral direction into the floodplain depends on the local stream velocity, and on grainsize-dependant settling rates. Multiple grainsize classes are independently tracked.
Floodplain deposition is an event-driven system, only peak discharge events cause overbanking, flooding and perhaps channel avulsion. The computational architecture of AquaTellUs preserves stratigraphy by event, allowing for preservation of information of depositional layers of variable thickness and composition.
We here present experiments that show the pronounced effect of different probability density functions for river discharge and sediment load, i.e. flooding recurrence times, on the stratigraphic architecture. +
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Floods can be devastating to society and the environment. Recent flood events around the globe, such as Harvey and Irma for instance, have been disastrous and broke records in damage and loss of life. Flood disasters often operate at spatial and temporal scales that far exceed local and regional, or even national, assessment and response capabilities. There is no doubt that remote sensing observations of floods, particularly from satellites, can be of great value. Earth observation (EO) data of floods can either be used directly through numerous services providing flood maps and other datasets, or indirectly through integration with hydrodynamic models simulating events continuously in time and space. In this project, we demonstrate the value of satellite flood maps for Harvey 2017 and Twitter feeds during the event for integration with a forecast inundation model (LISFLOOD-FP). Initial results are illustrated and we discuss current challenges and next steps. +
Flow network models are commonly used to study the formation and evolution of karst conduit systems and subglacial conduit systems. Such models involve: 1) numerical solution of flow within the network, and 2) calculation of the rate of change of conduit or fracture size within each segment of the network. Solution of flow and conduit growth is alternated to simulate long-term evolution of the system. Head loss equations, such as the Darcy-Weisbach or Hagen Poiseuille Equations, and a prescription of flow conservation at conduit junctions, are used to iteratively solve for flow within each segment of the network. In the case of karst development codes, discharges within the network are used along with kinetic rate equations to calculate transport and dissolution rates within every conduit segment. For subglacial systems, pressure head and frictional energy dissipation determined from the flow solution are utilized to calculate conduit growth by ice melting and closure due to ice creep. The Landlab modeling environment and associated gridding library greatly ease the development of a flow solver. Here we present the first stages of development of a conduit evolution code within Landlab, with applications both to subglacial and karst systems. Future work will focus on coupling landscape evolution models with network growth models to examine interactions between surface and subsurface processes. +
Flow routing calculations are routinely performed in geomorphic and hydrologic analyses. These require an appropriate flow-routing surface, which is generally a digital elevation model which has been pre-processed to remove all depressions from its surface. This allows the flow-routing surface to host a continuous, integrated drainage network. However, real landscapes contain natural depressions that can store water and break up the drainage network. These are an important part of the hydrologic system, and should be represented in flow-routing surfaces. The challenge is in removing from a DEM only those depressions which would be filled under reasonable hydrologic conditions at a given location, and not all depressions indiscriminately. To address this problem, we developed FlowFill, an algorithm that routes a prescribed amount of runoff across the surface in order to flood depressions, but only if enough water is available. This method conserves water volume and allows a user to select a runoff depth that is reasonable for the region of interest. Typically, smaller depressions or those in wet areas or with large catchments are flooded, while other depressions may not be completely filled, thus permitting internal drainage and disruptions to hydrologic connectivity. Results are shown at a sample location using a range of runoff depths, with the resulting flow-routing surfaces with filled and unfilled depressions and the drainage network structure associated with the result. +
Fluid-driven granular flows sculpt Earth's surface through processes such as soil creep, landslides and debris flows, and river bed-load and suspended sediment transport. In the case of river bed-load transport, grains may move by rolling, sliding, and jumping within a thin layer known as bed-load layer. In this layer, it is common for grains to segregate by size (a process that has been extensively studied) or shape, which has only recently been recognized as an important control. Here we perform numerical simulations to examine how shape-driven particle segregation is controlled by 1) purely granular interactions and 2) fluid-granular dynamics. To isolate granular dynamics, we construct a DEM model using LIGGGHTS to examine segregation of dry grains of different shapes in a rotating drum. To fold in the role of fluid drag, we use a CFD-DEM model (OpenFOAM + LIGGGHTS) to study particle segregation in open channel laminar flow. To efficiently simulate different shapes, we use bonded spherical particles to construct spheres, cubes, and cylinders. For the former, we use a horizontal cylinder filled with the same particles, and rotate it at low angular velocities. Meanwhile, for the latter, we set a periodic channel filled with spherical and non-spherical particles, of equal mean volume, sheared by a viscous Couette flow which imposes enough shear stress to move the particles by bed-load transport. For both, we investigate the statistical properties of the segregation by size and shape that non-spherical grains experience in the systems by tracking hundreds of individual trajectories throughout the entire bed, and the mechanisms involved that are mainly driven by particle collisions and fluid-grain interactions. These results illuminate the role of grain shape in controlling sediment transport, with implications for natural rivers, hillslopes, and aeolian systems. +
Fluvial bedload is a fundamental process by which coarse sediment is transferred through landscapes by fluvial action and is characterized by cyclic sequences of particle motion and rest. Bedload transport has many complex physical controls but may be well described stochastically by distributions of grain step length and rest time obtained through tracer studies. However, none of these tracer studies have investigated the influence of large wood on distributions of step length or rest time, limiting the applicability of stochastic sediment transport models in these settings. Large wood is a major component of many forested rivers and is increasing because of disturbances such as wildfire and insect infestations as well as the use of wood in rivers as part of ‘natural flood risk management’ practice in the UK. This study aims to investigate and model the influence of large wood on grain-scale bedload transport.
St Louis Creek, an alpine stream in the Fraser Experimental Forest, Colorado, is experiencing increased wood loading resulting from the infestation of the mountain pine beetle in the past decades. We inserted 957 Passive Integrative Transponders (PIT) tagged cobbles in 2016 upstream of a wood loaded reach and measured and tagged >20 pieces of large wood in the channel. We resurvey the cobbles and wood on an annual basis after snowmelt, building distributions of rock-step lengths and rest time distributions as well as observing any changes and transport of large wood. Additionally, we are developing novel active tracer tags, with integrated accelerometer technology, which will help to constrain these distributions and investigate the influence of woody debris.
We observed increased probabilities of grain deposition around large wood in the first 3 years of resurvey data, and preliminary statistical analysis suggests a significant influence of wood presence, and its relative stream position, on transport likelihood and distance, although additional annual data is required to verify its reproducibility. Over the next two snowmelt seasons, active tags will provide detail on the transport behaviour of cobbles at unprecedented levels, allowing us to refine stochastic bedload transport models in environments where biota is significantly interacting with earth surface processes.
Fluvial deltas have worldwide socio-economic importance as human development and infrastructure centers and provide several ecosystem services, including storm protection and nursery habitats. Their subsurface architecture also holds clues to past climate and sea-level change that can be reconstructed from stratigraphy. A significant challenge in inverting stratigraphy is separating the signals of external forcing, such as variations in sea level, and internal processes, such as the dynamics of the fluvial surface and channel network variations. In a previous work, we analyzed laboratory flume data from the Tulane Delta Basin using an experimental run with oscillating sea level conditions and constant sediment supply. We found that the dynamics of the fluvial surface play an important role in delaying the response of the upper portion of the subaerial topset. To further quantify this phenomenon, we couple this flume experiment with a numerical modeling framework that integrates the topset with a subaqueous offshore region or foreset. The numerical model can explain the topset slope, convexity dynamics, and sediment partitioning between the topset and the foreset under sea level variations. For example, it captures how during sea-level rise (SLR), low sedimentation near the topset's center reduces the subaerial slope and increases convexity, while during sea-level fall (SLF), high sedimentation increases the slope and concavity. Moreover, the model can explain the counterintuitive observation of higher sediment topset bypass to the foreset under SLR than SLF due to the reduction in subaerial slope, partially explained by a higher presence of active channels during SLR than SLF. These results underscore the importance of internal processes such as fluvial surface and channel dynamics, which can result in net erosion during SLR and net deposition during SLF, potentially complicating the reconstruction of paleo sea-level from deltaic deposits. +
Fluvial incision patterns help us understand the role of precipitation in river formation and evolution. The effects of drainage area, sediment supply and precipitation are closely linked and disentangling them is a challenging task.
In this study, we model different precipitation scenarios and use the stream power law to analyse river profiles. We focus on the analysis of the χ coordinate, a transformation of the stream-power law to capture changes in slope with distance downstream. The value of this coordinate is controlled by the concavity index, θ, which sets the steepness of the rivers downstream.
Similar χ profile shapes can be caused by different precipitation patterns, tectonic forcings or lithologies. However, choosing different θ coefficient values will lead to patterns similar to those arising from the natural forcings above, distorting the original physical signal.
In this study, we use the modelling framework Fastscape to generate landscapes that evolve to steady state under different precipitation scenarios. We test multiple precipitation models and calculate the χ profiles of the resulting simulated rivers using LSDTopoTools. We complete the analysis by comparing the model results to real topographic data from sites featuring a strong precipitation gradient, such as the Pyrenees, the Alburz mountains and the Andes.
This piece of research provides further insight on the importance of constraining the θ coefficient in χ profiles, in particular when disentangling the role of precipitation in river incision mechanisms. +
Fluvial incision since late Miocene time has shaped the modern transition between the Central Rocky Mountains and the adjacent High Plains of North America. Incision has formed a distinctive pattern of deep gouges at the mountain front centered around large drainages, most notably the Arkansas and South Platte Rivers. While there is a clear contrast in material strength and erodibility between the crystalline rocks that comprise the core of the mountains and the sedimentary packages that overlie the plains, researchers seldom account for this contrast when attempting to model the geomorphic evolution of the plains. In this study we set an explicit boundary across which erodibility changes from a value representative of granite, for the Central Rockies, to a value representative of coarse sandstone, for the High Plains. We then evolve the landscape with constant, uniform uplift and fluvial incision with sediment transport dependent upon a characteristic transport length. We find that with no external forcing beyond steady uplift and even on a landscape of modest gradient, it is possible to recreate deep incision at the mountain front simply by running water across substrates with highly contrasting erodibilities. This preliminary result has applications to future studies of the geomorphic evolution of the High Plains as it causes us to re-evaluate the sensitivity of this landscape to the material properties of the mountains and plains. In future work, this may guide us to look more closely at intrinsic properties of the landscape as an explanation for geomorphic expression before considering external forces. +
Fluvial sediment dynamics play an important role in the functioning and connectivity of the earth’s natural systems. It is not only one of the primary drivers of landscape development and channel morphodynamics, but also has important implications for water resources, ecology, geochemical cycling, and socio-economic aspects. Although anthropogenic influences are a major cause of changes in river sediment transport processes, it is widely accepted that these processes are also sensitive to climate change. Future climate changes particularly rises in temperature driven by increased greenhouse gas emissions, are projected to considerably impact 21st-century precipitation distribution which will alter fluvial processes, soil erosion and sediment loads worldwide. Predicting the responses of riverine fluxes to future climate is, therefore, vital for the management of fluvial systems. In this study, we conduct a global scale analysis of future suspended sediment and water discharge dynamics in response to the changing climate. We use a spatially and temporally explicit global scale hydrogeomorphic model, WBMsed. Changes in the earth’s climate system were obtained by forcing the model with downscaled precipitation and temperature projections generated by multiple General Circulation Models (GCMs), each driven by four Representative Concentration Pathways (RCPs). We investigate climate-induced spatial and temporal trends and variability in global suspended sediment loads and river discharge dynamics in the 21st century. +
Fluvial terraces are commonly interpreted as recorders of past environmental (e.g. tectonic or climatic) conditions. However, controls on terrace formation through river incision, and on the destruction of terraces through lateral erosion are poorly understood. Here, we present results from a physical experiment performed at the St. Anthony Falls Laboratory that provide insights into the formation and preservation potential of alluvial terraces, into dynamics of alluvial valley width, and the dependence of these parameters on external forcings: primarily on river response to base level fall. The model was performed in a wooden box with dimensions of ~4 meters by ~2.5 meters by ~0.5 meters, which was filled with silica sand with a unimodal grain size distribution (D50= 0.14 mm). Sediment and water were mixed and fed into the box via a gravel diffuser to inhibit scour. A single channel incised down to the base level, which was steadily lowered by a weir. Six experiments were performed, each with a constant water discharge of 0.1 L/s and a sediment flux of 0.022 L/s, and with a base-level fall rate of 0mm/hr, 25mm/hr, 50mm/hr, 200mm/hr, 300mm/hr, and 400mm/hr. We collected aerial photographs every 20 seconds and digital elevation models (DEMs) every 15 minutes throughout each experiment. Terraces formed in the experiments with base level fall due to incision and headwards knickpoint retreat. Major sidewall collapses and progressive valley widening were observed and controlled by the lateral migration of the channel. +
Fluvial valley width is determined by a combination of factors including regional lithology and drainage organization, as well as regional glacial and uplift history. In both topographic analysis and numerical modeling-based studies, valley width has been observed to follow a power law scaling relationship with drainage area. Local to regional scale studies have also demonstrated the influence of lithology, differential uplift, and drainage reorganization on this relationship. Yet, significant uncertainty remains regarding how these trends extend to the scale of large river networks and how they are influenced by transient forcing. The Upper Mississippi River Valley, initially incised during the early Pleistocene, presents a case study that encompasses a wide range of valley forms likely influenced by some combination of these factors, including by not limited to Spatially variable glacial history, bedrock lithology, and punctuated drainage reorganization events. This research aims to analyze the variable contribution of lithology, downstream changes in drainage area and history of reorganization, and regional variability in glacial isostatic adjustment in determining downstream trends in valley morphology. By isolating these effects, we aim to determine whether there is an extractable signal of the conditions during initial valley incision embedded in modern valley topography. Here we present a dataset of high-resolution valley aspect ratio and curvature, paired with longitudinal trends in drainage area and bedrock lithology. This is compared with empirical expectations for valley width scaling. Preliminary analysis found an overall downstream valley widening trend, however with multiple perturbations, including narrow gorges, and locally beveled valley walls caused by a combination of lithologic transitions and differing drainage integration histories. +
Following pioneering modeling work examining the evolution of wave-influenced deltas (Ashton et al., 2013; Nienhuis et al., 2013), we coupled the River and Floodplain Evolution Model (RAFEM) to the Coastline Evolution Model (CEM). Results of a recent suite of model experiments (conducted using the CSDMS software stack and Dakota) lead to new insights: 1) The preferred location of avulsions (a distance from the river mouth scaling with the backwater length), previously observed in laboratory models and in the field, can arise for geometric reasons that are independent of those recently suggested (Chatanantavet et al., 2012; Ganti et al., 2016). This alternative explanation applies when the river longitudinal profile tends to diffuse more rapidly than the floodplain longitudinal profile. 2) Although the timescale for avulsions is expected to increase with increasing wave influence (Swenson, 2005), we find that this depends on the angular wave distribution. When wave influence is strong and the angular mix of wave influences tends to smooth a nearly straight coastline (coastline diffusion), progradation is slowed and avulsions delayed. However if the angular wave distribution produces anti-diffusive coastline evolution, a strong wave influence still leads to cuspate delta shapes, but avulsions are barely delayed. 3) Although increasing sea-level-rise rate is expected to cause more rapid avulsions, and does in laboratory deltas, we unexpectedly find that this is not true for river-dominated deltas in our model (or for anti-diffusive wave climates). The explanation, involving the role of sea-level-rise related transgression (or decreased progradation), raises potentially important questions about geometrical differences between laboratory deltas and natural deltas. 4) The magnitude and timescale of autogenic variability in sediment delivery rates at the river mouth depends on wave climate, sea-level-rise rate (for some wave climates), and on the amount of super elevation of the river channel (relative to the surrounding floodplain) required to trigger avulsions.
* Ashton, A. D., Hutton, E. W., Kettner, A. J., Xing, F., Kallumadikal, J., Nienhuis, J., and Giosan, L. (2013), “Progress in coupling models of coastline and fluvial dynamics,” Computers & Geosciences, 53, 21–29.
* Chatanantavet, P., Lamb, M. P., and Nittrouer, J. A. (2012), “Backwater controls of avulsion location on deltas,” Geophysical Research Letters, 39.
* Ganti, V., Chadwick, A. J., Hassenruck-Gudipati, H. J., Fuller, B. M., and Lamb, M. P. (2016b), “Experimental river delta size set by multiple floods and backwater hydrodynamics,” Science advances, 2, e1501768.
* Nienhuis, J. H., Ashton, A. D., Roos, P. C., Hulscher, S. J., and Giosan, L. (2013), “Wave reworking of abandoned deltas,” Geophysical research letters, 40, 5899– 5903.
* Swenson, J. B. (2005), “Relative importance of fluvial input and wave energy in controlling the timescale for distributary-channel avulsion,” Geophysical Research Letters, 32.
