2011 -2013 Marine Geology and Geophysics (OCE 1061380)
Catchments and Coastlines--The Influence of Sediment Load and Type on Delta Morphodynamics and Deposits, $149,338
ABSTRACT: The various shapes of river deltas strongly control their ecological function, resilience to perturbations, and the stratigraphy of their deposits. These shapes were thought to be dependent mainly upon downstream processes, such as the wave- and tidal-power of the ocean basin and the energy flux of the river, but recent work has suggested that upstream controls, such as load and sediment type (i.e. cohesive vs. noncohesive sediment) may also be a major factor controlling delta morphology. Here we propose a theoretical and field study of how sediment load and type, and thus source terrain, control a delta’s planform morphology and internal stratigraphy. A series of numerical experiments using Delft3D, a morphodynamic physics-based model simulating 3D fluid flow and sediment transport, will extend the parameter space of earlier work by varying sediment fluxes and grain size distributions of a parent river subject to one flood wave per year. A final set of experiments will include the effects of wave and tides. For a given set of input conditions, the experiments will predict delta planform, first-order facies distributions, sandbody geometries and connectivity, distribution of mud drapes, and through-going surfaces important for sequence stratigraphic interpretation. Analysis of the evolution will allow us to understand the physical processes leading to each particular set of delta characteristics. The numerical predictions will be compared to cores, serial aerial photography, bathymetry, and ground penetrating radar datasets from modern deltas representing end-members of the modeling results. Candidate deltas include Wax Lake and Mossy deltas of Louisiana and Saskatchewan, and El Coyote fan delta on the western coast of the Gulf of California, where already existing data will be supplemented by limited fieldwork, Pleistocene shelf-edge deltas such as off Apalachicola, FL, and ancient deltas such as the Cretaceous Ferron and Panther Tongue deltas of Utah.
2011-2014 Geomorphology and Landuse Dynamics (EAR 1123847) Defining controls on incisional avulsions in alluvial basins, $112,307
ABSTRACT: Avulsion occurs when flow is diverted out of a river and into a new flow path on the floodplain. This can be catastrophic for people living along rivers, and over geologic time scales it is the fundamental process that builds fluvial stratigraphy. Unfortunately, mitigating hazards and predicting stratigraphy associated with avulsions is difficult because we still do not understand what controls the timing, location, or style of river avulsion. Incisional avulsions—those in which new channel locations are established through erosion rather than deposition—remain poorly understood even though they were common in some ancient river systems. We propose a combined field and modeling study to identify controls on incisional avulsions. Our broad goal is to define the sedimentologic and paleohydraulic conditions associated with incisional avulsions. We hypothesize that incisonal avulsions are prevalent in settings prone to floodplain incision, and that occurs in floodplains that are 1) steep, 2) topographically rough, 3) dry and sparsely vegetated, and 4) lack abundant overbank suspended-sediment supply. We will test this hypothesis using Delft3D, a physics-based morphodynamic model that creates self-formed avulsing channels, and with detailed field data from the Ferris Formation (Cretaceous/Paleogene, Wyoming) and Wasatch Formation (Eocene, Utah/Colorado), where we can unambiguously measure channel and floodplain characteristics for more than two hundred paleoavulsion deposits.
2011-2016 Frontiers in Earth Systems Dynamics A dynamic delta collaboratory, $5,000,000, 14 co-PIs, $300,000 to Edmonds
ABSTRACT: River deltas represent a major Earth-surface system with societal need. Low-lying, ecologically productive, and inhabited by millions of people, deltas also lie directly in the path of a confluence of ongoing changes: nutrient overloading from agriculture; accelerated subsidence and sea-level rise; effects of land use and navigation; and changing hydrology and sediment supply. The overall objective of this proposal is to develop tested, high-resolution, quantitative models incorporating morphodynamics, ecology, and stratigraphy to predict river delta dynamics over engineering to geologic time-scales, and to specifically address questions of system dynamics, resiliency, and sustainability. We will do this by establishing the Delta Dynamics Collaboratory (DDC) for multi-investigator, interdisciplinary investigations of river delta sedimentary and ecologic dynamics. The lead institution for DDC will be the University of Texas, Austin, currently the center of delta prediction efforts for the National Center for Earth-surface Dynamics (NCED). The collaboratory will comprise two main work centers: a field observatory and a virtual modeling center, together with supporting experimental facilities. The observatory will be at Wax Lake Delta, a manageably small (140 km2), actively growing delta about 100 km west of the main Mississippi Delta birdsfoot. The main observational goal will be to create a network of self-activating sensors to monitor delta behavior during major events (storms, river floods) that will complement an intensive survey program to measure ecosystem properties and relate them to high-resolution topography, bathymetry, and flow fields. The virtual modeling center will be hosted by the Community Surface Dynamics Modeling System (CSDMS) at University of Colorado, where it can contribute to an evolving library of modules for computation and visualization of geomorphic and sedimentary systems, including access to many of the existing delta models. These two centers will be supported by experimental programs at the universities of Minnesota, Illinois, and Texas, and computational programs at Penn State, Boston College, Louisiana-Lafayette, Minnesota, Illinois, and Texas.