CAREER: Understanding Processes related to Arroyo systems, southern Utah

Utah State University, Logan UT

Investigators

Abstract

EAR-1057192 CAREER: Understanding Processes related to Arroyo systems, southern Utah Tammy Rittenour, Utah State University This CAREER grant project is designed to test hypotheses about the driving mechanisms that have led to repeated (and poorly understood) entrenchment and re-aggradation events (arroyo cut-fill cycles) in six adjoining semi-arid drainages in southern Utah. Methods and proposed activities follow three research objectives, each designed to approach this longstanding 'arroyo problem' from different angles. These are 1) developing a detailed and well-dated stratigraphic record of past cut-fill cycles (using optically stimulated luminescence, or OSL, and radiocarbon dating) and completing geomorphic mapping and GIS analysis of the watersheds, 2) investigating the processes that drive aggradation by characterizing sediment production and erosion rates using cosmogenic radionuclide analysis (10Be) of channel sediment and an innovative application relating OSL characteristics and sediment erosion rates, and 3) understanding the driving forces behind rapid arroyo entrenchment by investigating the modern flood hydrology and inter-annual discharge variability as well as using tree-ring chronologies to extend the instrumental record of precipitation and discharge. Together, these research methods and aims are designed to bring new data and analyses to bear on the 'arroyo problem? --a long-standing geomorphic and land management challenge in the southwestern US. At the turn of the last century (1880 +/- 30 AD), numerous rivers and streams in the southwestern US rapidly incised into their floodplains forming deep arroyos (up to 30m deep within years to decades), and left settlements and homesteads perched above their water sources. This rapid event is one of the most significant geomorphic events in the SW US and has caused numerous environmental and economic problems. This project will use a multi-tiered set of modern analyses in six adjoining drainages in southern Utah to re-address long-standing questions related to the 'arroyo problem'. This research on the response of semi-arid river systems to past change is especially timely given projected changes in drought frequency and flood severity under future greenhouse gas conditions. This CAREER grant has a significant education component and will include outreach to the local rural school districts and land managers within the regions impacted by the streams being studied.