PARENT SESSION
Symposium #18: Understanding and Restoring Riparian Ecosystems at Risk: The Great Basin Ecosystem Management Project.

Organized by: JC Chambers and JR Miller
Wednesday, August 7. 8:00 AM to 11:30 AM. Turquoise Ballroom, TCC.

Fluvial geomorphic responses in central Nevada to natural and anthropogenic disturbances during the late Holoene.

Miller, Jerry^*,1, House, Kyle², Germanoski, Dru³, Tausch, Robin⁴, Chambers, Jeanne⁴, ¹ Department of Geosciences & Natural Resources Management, Cullowhee, NC² Nevada Bureau of Mines and Geology, Reno, NV³ Department of Geology and Environmental Geosciences, Easton, PA⁴ USDA Forest Service, Reno, NV

ABSTRACT- Stratigraphic and morphologic investigations of small (<100 km²), upland watersheds in central Nevada indicate that in spite of differing tectonic and geologic settings, geomorphic responses to disturbances during the late Holocene were similar in a large number of basins across the region. Of primary significance was a period of intense hillslope erosion and valley aggradation between approximately 1920 and 2580 YBP. These events correlate to a shift from moister to drier climatic conditions documented by paleoclimatic proxy data. Aggradation was followed by channel incision that began at about 1900 YBP in response to a depletion of fine-grained sediment within the hillslope sediment reservoirs. Incision has continued to dominate these upland channels through the remainder of the Holocene. However, the magnitude and rate of channel incision varies between basins and along the riparian corridor of a given basin. A significant difference is the degree to which alluvial fan deposits constructed at the mouth of small, side-valley tributaries have been truncated during the past 2000 years. The geomorphic responses documented within upland watersheds differ in terms of the timing, magnitude and style from those observed along the Humboldt River, a watershed with an area that is several orders of magnitude larger. These data clearly illustrate the importance of both spatial scale and geomorphic history on the behavior of fluvial systems in the Great Basin of central Nevada.

KEY WORDS: Geomorphology, Restoration, Climate