CSDMS 2016 annual meeting poster KimberlyMiller
Experimental reproducibility of results of flow intermittency on delta dynamics
Brandon McElroy, University of Wyoming Laramie Wyoming, United States.
Wonsuck Kim, University of Texas at Austin Austin Texas, United States.
Abstract:
In order to simplify the complex hydrological variability of flow conditions, experiments modeling delta evolution are often conducted using a representative “channel-forming” flood flow and then results are related to field settings using an intermittency factor, defined as the fraction of total time at flood conditions. Although this intermittency factor makes it easier to investigate how variables, such as relative base level and/or sediment supply, affect delta dynamics, little is known about how this generalization to a single flow condition affects delta processes. With changes in climate causing changes in magnitude, as well as variability, of the hydrology of these coastal systems, it is important to understand how intermittent flows will affect these environments. We conducted a set of laboratory experiments with periodic flow conditions to determine the effects of intermittent discharges on delta evolution. Because the Sediment Experimentalist Network (SEN) has stated that reproducibility of experimental results is one of the grand challenges facing our scientific community, we have conducted similar experiments at both the University of Texas at Austin and the University of Wyoming to compare and determine generalized conclusions. During these experiments, flood periods with a set water discharge and sediment supply, cycles between periods of base flow where the sediment supply is turned off. We find that during base flow periods, channels tend to incise resulting in a small yet finite amount of shoreline progradation even though sediment is not input to the system. On the other hand, channels will aggrade during floods when sediment is turned back on. The system must adjust between these two different equilibrium states for each flow condition. These results suggest that the adjustment timescale between differing flow conditions is a factor in determining the overall shape of the delta and behavior of the fluviodeltaic channels. We conclude, periods of base flow when topset sediment is reworked, may be just as important to delta dynamics as periods of flood when sediment is supplied to the system.
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