Application of a Luminescence-Based Sediment Transport Model

Quantifying the transport history of sand is a challenging but important goal in geomorphology. In this paper, we take a simple idea that luminescence is bleached during transport and regenerates during storage, and use this as a basis to re-envision luminescence as a sediment tracer. We apply a mathematical model describing luminescence through an idealized channel and reservoir system and then compare this idealized model to real rivers to see if luminescence can reproduce known sediment transport data. We provide results from application of this luminescence method in three rivers from the mid-Atlantic region of the United States. This method appears promising. However, as a river system diverges from idealized conditions of the mathematical model, the luminescence data diverge from model predictions. We suggest that spatial variation in the delivery of sediment from hillslopes can be reflected in the channel sediment luminescence and that luminescence acts as a function of landscape dynamics. Plain Language Summary How fast sediment gets from point A to point B in river systems is a surprisingly hard question to answer. Many of the scientific techniques we have are usable only over a span of years. This is a problem if one wants to compare current rates of sediment transport with long-term averages to understand the effects of climate change. In this paper, we present and apply a new method using luminescence, a property of sand that changes based on sunlight exposure. Luminescence is very interesting from a scientific perspective because it increases while sand is buried in river deposits and decreases while in sunlight. Because sand grains see different amounts of sunlight while traveling in river systems, we set out to connect measurements of luminescence with sediment transport rates. We found that luminescence appears to be able to tell us about sediment transport over very long time periods, which suggests that luminescence can be an exciting new tool. However, we found that the more complicated the river system, such as when there is a lot of human modification, the more difficult it is to use luminescence. Overall, luminescence shows promise toward answering scientific questions about sediment transport.