Eroded Away: Exploring the Causes of Dynamic River Sediment

Science Center, Bent Corridor

This summer I had the opportunity to work in the Geology department to analyze river sand taken from various sites within the Chinese Mekong, Salween, and Red River watersheds and investigate erosion activity. The goal of my research was to determine how influential monsoons are to displacing sediment. When interacting with monsoon environments, it is thought that most of the sediment is moved during the wet season, rather than during sporadic large storms. To do this I looked at pairs of in-channel and overbank samples from Yunnan, China and collected in January 2014, during the dry season; we assume in channel samples are material transported during the dry season while overbank samples are material transported during the monsoon. I had to measure the activity of unsupported 210Lead in each, an isotope that precipitates from the atmosphere and is found within the top 20cm of the soil. This trait allows it to be a good indicator for surface erosion. Preliminary results suggest that there are not systematic trends with sediment source for the region. One could extrapolate from these findings that other influences are at work here as well, things like climate, topography and human land use cannot be ignored. In the future we would hope to look at even more sites, twenty-nine in total, while also taking these external factors into account.