ANALYZING A POTENTIAL LANDSCAPE RESPONSE TO THE DEVELOPMENT OF THE LOWER COLORADO RIVER, NEVADA, USA

Despite confining the timing of the Colorado River’s development through the Lake Mead area in southeastern Nevada to about 5.6 Ma (Faulds et al., 2016), our understanding of the Colorado River’s effects on the regional inherited topography are still unclear. In this contribution, we implement computational topographic analyses to interpret the erosional response to a potential increase in stream power driven by the arrival of the Colorado River to southern Nevada. The watershed of the Lower Colorado River has a unique morphology that extends north from Lake Meade, eventually splitting into three elongated channels, two of which follow Basin and Range topography: The White River Valley and the Meadow Valley Wash. Both channels show evidence of basin capture events that have enlarged the watersheds, but the timing of those captures remains relatively unconstrained. We conducted geomorphic analyses using a 30-meter DEM and Chi Profiler software (Gallen and Wegmann, 2017) on the two main drainage channels and their tributaries and identified a suite of regional knickpoints within a band of elevations spanning ~675-850 m. The two primary trunk channels, the White River Valley and Meadow Valley Wash, contain knickpoints at ~800 m in elevation. The tributaries of the White River Valley contain 9 knickpoints between 710 and 840 meters; the Meadow Valley Wash tributaries contain 6 knickpoints between 675 and 850 meters. We posit these knickpoints may represent a collective channel response to the development of a throughgoing Colorado River. Future work will implement landscape evolution modeling to evaluate whether this suite of knickpoints could have been formed due to the arrival of the Colorado River and a resulting increase in stream power.