2014 GSA Annual Meeting in Vancouver, British Columbia (19–22 October 2014)

Paper No. 39-4
Presentation Time: 9:45 AM

MONITORING THE DESTRUCTION AND NATURAL RECOVERY OF A MONSOON-DOMINATED STREAM SYSTEM AFTER A WILDFIRE DAMAGES ITS WATERSHED, STOUT CANYON, UTAH


CHRISTENSEN, Peter Daniel, Physical Science, Southern Utah University, 264 South 800 West, Cedar City, UT 84720 and HARGRAVE, Jennifer E., Physical Science, Southern Utah University, Cedar City, UT 84720, peterdanielchristensen@gmail.com

The damage that occurs to streams and its recovery after its watershed has been destroyed by a wildfire is well documented in streams that have its high flow event occur during spring runoff. There is very little data however, regarding the destruction and natural recovery of streams that have high flow events during the late summer monsoon rains. Stout Canyon (a tributary to the East Fork of the Virgin River) located about 25 miles North of Cedar City, Utah is a monsoon dominated stream system whose watershed was damaged by the Shingle Fire of 2011. The destruction and recovery was documented by using the Rosgen Field Methods. The field data was then compared to similarly collected data from snow melt runoff dominated streams in the Rocky Mountain area whose watershed have also been damaged by wildfires.

The results showed that Stout Canyon substrate initially underwent a fining process but returned to near pre fire conditions within three to four years. Bankfull indicators also began to reappear at Stout Canyon three years after the fire suggesting that the stream is beginning to recreate its flood plain. Both of these results match the general trend that occurs in spring runoff dominated systems. The major difference between Stout Canyon and other streams appear in its bank geometry. In most streams it is observed that the largest changes in bank geometry will occur within the first year after the fire with minor alteration occurring in the subsequent years and the banks re-stabilizing within about five years. Stout Canyon’s banks, however, saw the most alteration during the second year after the fire and it is continuing to undergo major alteration with no signs of stabilizing four years after the fire. This may be a result of the fact that monsoon-caused-high-water-events vary greatly from year to year, whereas snow melt runoff caused high events are generally consistent. The inconsistent high water events on streams like Stout Canyon make it difficult for the stream banks to stabilize as efficiently and quickly as observed on other streams in the Rocky Mountain Region.

Handouts
  • Peter Christensen Poster GSA 2014.pdf (1.5 MB)