Use of cosmogenic nuclides to understand relations among climate change, erosion rates, and landscape response in Grand Staircase region of Colorado
Class
Article
Department
Geology
Faculty Mentor
Tammy Rittenour
Presentation Type
Poster Presentation
Abstract
Over 81% of all streams in the southwest United States are ephemeral or intermittent. Given the delicate balance between sediment supply and discharge, these streams are sensitive monitors of landscape response to past and future climate change. At the turn of the 20th century (AD ~1880), many streams in the SW suddenly incised up to 30 m into their floodplains forming steep-walled arroyos entrenched into cohesive fine-grained valley-fill alluvium. Settlements in the semi-arid SW are dependent on water availability and during historic arroyo entrenchment, widespread channel incision and floodplain abandonment caused communities to become disconnected from water resources and led to abandonment of some towns. Importantly, climate models predict greater temperature extremes and more frequent floods and droughts in the SW US. Investigating geomorphic response to past climate change enables us to better understand how the landscape might respond to future climate change. Chronostratigraphic reconstructions indicate that during the mid-late Holocene these systems underwent multiple periods of rapid episodic entrenchment followed by slow re-aggradation. This research investigates the role of allogenic forcing (climate change) and autogenic processes on cut-fill dynamics. A stream channel maintains a dynamic equilibrium in which the channel bed adjusts its slope and geomorphic form in response to changes in discharge and sediment supply. This study tests if temporal or spatial disparities in sediment supply have influenced the timing and location of arroyo aggradation and entrenchment. We measured in-situ 10-Be in quartz from alluvial and colluvial sediment in Kanab Creek and Johnson Wash to quantify catchment-average erosion rates. Samples were collected from modern channels throughout the watershed and from dated alluvial packages preserved in arroyo walls. Results quantify spatial and temporal variability in sediment supply throughout the two watersheds as a function of lithology, slope, elevation, contribution of sediment stored in valley-fill, and time. Moreover, 10-Be results from dated Holocene alluvium will be used to evaluate if climate change has influenced sediment supply and arroyo cut-fill dynamics.
Start Date
4-9-2015 3:00 PM
Use of cosmogenic nuclides to understand relations among climate change, erosion rates, and landscape response in Grand Staircase region of Colorado
Over 81% of all streams in the southwest United States are ephemeral or intermittent. Given the delicate balance between sediment supply and discharge, these streams are sensitive monitors of landscape response to past and future climate change. At the turn of the 20th century (AD ~1880), many streams in the SW suddenly incised up to 30 m into their floodplains forming steep-walled arroyos entrenched into cohesive fine-grained valley-fill alluvium. Settlements in the semi-arid SW are dependent on water availability and during historic arroyo entrenchment, widespread channel incision and floodplain abandonment caused communities to become disconnected from water resources and led to abandonment of some towns. Importantly, climate models predict greater temperature extremes and more frequent floods and droughts in the SW US. Investigating geomorphic response to past climate change enables us to better understand how the landscape might respond to future climate change. Chronostratigraphic reconstructions indicate that during the mid-late Holocene these systems underwent multiple periods of rapid episodic entrenchment followed by slow re-aggradation. This research investigates the role of allogenic forcing (climate change) and autogenic processes on cut-fill dynamics. A stream channel maintains a dynamic equilibrium in which the channel bed adjusts its slope and geomorphic form in response to changes in discharge and sediment supply. This study tests if temporal or spatial disparities in sediment supply have influenced the timing and location of arroyo aggradation and entrenchment. We measured in-situ 10-Be in quartz from alluvial and colluvial sediment in Kanab Creek and Johnson Wash to quantify catchment-average erosion rates. Samples were collected from modern channels throughout the watershed and from dated alluvial packages preserved in arroyo walls. Results quantify spatial and temporal variability in sediment supply throughout the two watersheds as a function of lithology, slope, elevation, contribution of sediment stored in valley-fill, and time. Moreover, 10-Be results from dated Holocene alluvium will be used to evaluate if climate change has influenced sediment supply and arroyo cut-fill dynamics.