EXPLORING WHAT CAN BE LEARNED FROM NORMALIZED CHANNEL STEEPNESS ACROSS THE STATE OF UTAH: FAULTING, UPLIFT, ROCK TYPE, AND PLATEAU INCISION

The relative steepness of river channels, normalized for drainage area (Ksn) and discharge (Ksn-q), can provide information about variations in tectonic uplift, rock strength, and the response of drainage networks to base level changes over timescales of 10⁴ – 10⁷ years. In this study, we used Topotoolbox and MATLAB to examine Ksn based upon analyses of the ALOS 30 m DSM within the State of Utah. Our analyses were restricted to upland areas within the Basin and Range Province (i.e., we did not examine channels within the valleys) and tributaries of the major rivers flowing through the Colorado Plateau that are located entirely within the State. We did not examine the Colorado, Green or San Juan Rivers themselves because their drainage areas extended beyond Utah. First order results within the Basin and Range show that Ksn clearly discerns greater uplift along the Wasatch front than other mountains of the Basin and Range and that Ksn is sensitive to variations in the resistance to erosion of strong versus weak rock units. Among the less active faults in the Basin and Range we also observe that Ksn does not correlate consistently with differences in Holocene to latest Pleistocene vertical slip rates. Where ranges are fault-bounded on one side, Ksn clearly illuminates which side of the range is actively uplifting. Where mountains are due to a horst structure, Ksn values are more symmetrical. Interestingly, we identified two ranges without Quaternary faults appearing in the State’s fault and fold database that have high Ksn values including the west side of the Pahvant Range and the east-west oriented Raft River Range in northwestern Utah. The Wasatch Plateau, which contains the Wasatch monocline to the west and the Joe’s Valley fault zone to the east, has among the highest Ksn values of anywhere on the Basin and Range side of the State. Finally, the highest Ksn values of anywhere in Utah are found in the major tributaries cutting through the Colorado Plateau and Uinta Mountains to join to the Colorado, Green, and San Juan rivers. We suspect that this reflects the geological youth of incision along these river systems cutting through Utah’s Canyonlands and borderlands of the Plateau. Our planned next steps are to test if Ksn-q can discern segmentation within the central Wasatch and to examine high resolution topographic data to see if there is evidence of Quaternary faulting along the Raft River and Pahvant Ranges.