Research Projects

Crowd Source Delta Classification

The current system of delta classification relies on interpretation of features, rather than the features themselves. Often, we are trained to combine the observation of a feature with the interpretation of how it got there. This method is so ingrained that we often do i this so automatically that we usually don’t even realize what we've done. To address this, we have devised a new and novel method to create a classification system based on features alone. We have created a data base of images of deltas (from the field, from experiments and from numerical models) removed of all color, scale and orientation. By asking people to classify the deltas based on whatever criteria they set, we believe that we may see some organizational structure that we have previously overlooked. We hope this game helps advance our understanding how deltas work: how they form, how they grow and react to change.

Click here to learn more about this project and to play Delta Shuffle.

Influence of offshore events on sediment mass balance in deltaic systems

Often, when we model fluvial sedimentation on large space and timescales, we focus on local controls (e.g. sediment and water supply), as well as the effects of relative sea level change. Shoreline often provides a boundary condition, which implies that offshore processes are merely acting as a passive sink for sediment accumulation. However, over long time scales, coastal rivers are strongly coupled to offshore and slope transport systems via the clinoform geometries typical of prograding sedimentary bodies. We adopt a “sink to source” view of sediment mass balance on coastal-plain rivers. We identify a variety of effects by which offshore processes influence the state of coastal rivers.

Transport of flocculated clay sediment

Models which describe the transport of fine grain sediment, such as clays, have been based on the idea that clays are transported as individual grains. However, clays are commonly transported in the form of aggregates due to flocculation. Flocculation changes the properties of the sediment by increasing the effective grain size and decreasing the effective density. The implication of these aggregates or flocs is that clay sediment can be transported as bedload material, which dramatically alters the way shale and mud deposits are interpreted. We are examining how well classical empirical equations of bedload transport (e.g., Meyer-Petter and Müller, 1948; van Rinj, 1984) capture the bedload transport of flocculated clay sediment when adjusted for properties such as grain size and density by conducting a series of experiments to measure the transport rate of flocculated clay sediment.

Video of the bedload transport of flocculated clay sediment.

Interaction of prograding deltas on a deformable substrate

Common models for the trigger mechanism of mass failures are eustatic models, which suggest that the rise and fall of sea level creates pore pressure changes that lead to slope instability. However, it has been noted that the abundance of mass failures cannot be accounted for by eustatic cycles alone. One possible explanation for the abundance of mass failures is the deformation of salt, where salt is mechanically weak rocks made mostly of halite. Recent work on salt basins in the Gulf of Mexico suggested a mechanism for the generation of mass failures through the deformation of salt by a prograding body. This deformation results in a structural high in the salt layer, which causes slopes to over steepen and fail. The mass failures generated then create more preferential loading on the salt basin, creating a cycle of salt deformation and landslide generation. We have conducted a series of experiments to investigate the role of salt tectonics on the generation of mass failure events.

Photo of an experiment of a cohesive delta (walnut sand and clay) prograding over a deformable substrate (corn syrup)

Connectivity of mud deposits

Cohesive sediment makes up two-thirds of the sedimentary rock record and covers much of the earth’s surface. Despite the volumetric prevalence of cohesive sediments, the dominate focus of research on sedimentary systems has been non‐cohesive sediment. Consequently, there has been limited research on how cohesive sediment is transported and deposited. This is particularly important for understanding the connectivity of reservoirs as larger scale and even in some cases smaller scale fine-grained deposits may act as significant baffles. To address these questions and to constrain the horizontal geometries and spatial relationships of fine grain deposits, we conducted an experiment using a highly cohesive sediment mixture. By using physical experiments, we can constrain and measure parameters which may difficult to measure in the field.

Temporal and spatial distributions of channel bars

Bars are depositional features located within and along a channel. These deposits are very important to understand as they have strong implications for fluid connectivity and reservoir modelling. To understand what factors influence the occurrence of bar deposition, we are collecting spatial and temporal statistics on bar deposition on experimental deltas that have been subjected to external influences (fluvial, tidal wave, subsidence and tectonic regime), allowing us to observe how these basinal forces alter the morphology and behavior of bar deposition.

Effect of cohesive sediment on deltaic morphology and behavior

Often, we have used physical and numerical models to understand factors which control morphology and properties of deltas (Paola et al., 2001; Geleynse et al., 2011). Few studies have looked at the role cohesion has on deltas (Edmonds et al., 2009; Hoyal et al., 2009; Martin et al., 2009a), as most models primarily focused on non-cohesive sediment (Paola et al, 2001; Kim et al, 2006; Martin et al., 2009b). The presence of clay can lead to complex behavior across differing scales and it is uncertain to what extent these effects influence large scale deltaic behavior. To investigate the influence of clay on delta properties, we built an experimental delta under various conditions (fluvial, tidal and waves). This allowed us to observe how the presence of clay alters the morphology and behavior of the delta. To determine the delta’s response to differing physical environments, we will be looking at the morphological response in the form of channel dynamics, avulsion rates, bar formation and shoreline complexity.

Video of an experimental cohesive delta.

Effect of fluvial, tidal and wave energy on deltaic systems

The most common way to classify deltas is through the Galloway method, which separates deltas into fluvial, wave and tidal dominated deltas. This classification of deltas relies on qualitative interpretation of subaerial geomorphology to determine the dominant process acting on the delta. However, it is important to note that this system relies on an assumption of what the dominant process is. We are working on ways to quantify this system by creating experimental deltas that subject a system to various fluvial, tidal and wave strengths to measure the impact this has on delta morphology.

Photo of an experiment of a experimental tidal delta.

Mass failures in weakly cohesive systems

Prior experiments on mass failures are often done by injecting a slurry (mixture of sediment and water) into ambient water, artificially creating these flows (e.g., Parker et al. 1987; Marr et al. 2001; Mohrig et al. 2003). While these studies have provided excellent insight into the behaviors of mass flows, we have yet to address the question of how these flows initiate and what factors influence the size and frequency of their occurrence. The idea behind this project was to create a mix of sediment that instead of producing uniform small grain flows on the foreset as sand does, might self-organize to create larger and more complex flows that would shed light on mass flow processes, which typically include substantial amounts of clay. For this project, we investigated how changes in sediment discharge are partitioned between failure events.

Video of mass failure experiments using walnut sand and kaolinite