Computer Modeling of Delta Growth Morphology to Understand Autogenic Behavior
The research project that is my current focus is concerned with autogenic processes that are active during delta formation. Autogenic processes are variant reactions of a system to constant or steady external forcing. Often times these autogenic processes have been explained by allogenic processes (Responses to non-steady external forces) such as: high-frequency eustatic variation, fluctuating climate effects on change in sediment yield, episodic subsidence to explain the cyclic nature of vertical sedimentary records. The existence of fundamentally two distinct sedimentary events can lead to interpretation problems of stratigraphic records. Studies of the autogenic processes have been directed at deltaic settings as they are locations of heavy sedimentation and thus thorough preservation of geologic records.
My work looks to compliment the results achieved by Erica Powell (2011, in review). These flume experiments reveal insight into the development of radially growing delta’s. The flume runs show that the shoreline can be analytically modeled as function of the cube root of time. Furthermore, increasing the sediment supply in a deltaic system will decrease the autogenic timescale. However, the increase in sediment supply does not proportionally reduce the autogenic timescale because the increase in sediment supply yields the secondary effect on the morphology of the fluvial system by developing a relatively larger fluvial buffer to be filled during times of sediment storage. In addition, increasing the water discharge in a deltaic system will lengthen the autogenic timescale by shaping the larger fluvial system while it deforms to a more highly organized channel network. This highly organized pattern tends to take a longer time to develop and increases the time necessary for storage and release processes.
By using a MatLab model developed by Matthew A. Wolinsky (University of Minnesota, Minneapolis), I establish scenarios similar to the flume experiments in which a delta is developing radially. In order to mimic the autogenic and random behaviors of natural systems, a noisy routing scheme is applied to the sediment flux. This introduces a variable which is a random uniformly distributed number that allows for unrepeatable patterns in sediment flux and thus development of delta morphology.
In order to properly understand the autogenic signatures, I have a great advantage in my research in that each run results in a wealth of data to be analyzed. By tracing geometrical parameters such as slope, shoreline, area etc… I will be able to assess the response of the delta growth and various times to constant forcing. In these runs the constant forcing is constant sediment yield. Once these patterns are visually assessed Fourier analysis and cross- correlation will hopefully allow for further identification of discrete signatures and patterns. The project aims to identify such patterns when latter base-level changes are implemented.
Advisor: Wonsuck Kim