Drainages and Runoff

There is an ongoing discussion both locally and in the media concerning the possible effects of the coming monsoon season on the Chiricahua Mountains.  With decreased ground cover resulting from the Horseshoe Two fire the likelihood of uncontrolled runoff increases. While many are pursuing flood insurance and the BAER team is assessing burned areas creating mitigation recommendations, it seemed worthwhile to examine the Chiricahua Mountain range and map individual drainage's to provide semi-quantitative estimates of possible areas where runoff may pose a problem.  Below are the results of mapping individual drainage's that flow east and south from the interior of the Chiricahua Mountains.  Nine drainage's were identified that start in the interior and flow east and south and include:

1. Turkey Creek drainage - 31.5 square miles
2. Silver Creek drainage -  10.2 square miles
3. Silver Peak drainage -  24.1 square miles
4.  Flys Peak drainage - 9.3 square miles
5.  Chiricahua Peak drainage - 22.5 square miles
6.  South Fork drainage - 36.4 square miles
7.  Sulphur Canyon drainage - 12.5 square miles
8.  Horseshoe Canyon drainage - 40.5 square miles
9.  Price Canyon drainage -  22.5 square miles

The surface area, based on the circumference of the outline and uncorrected for elevation change, follows each drainage.  The Silver Creek drainage received no fire and would be expected to behave normally in the coming monsoon season.  While the western portion of the Turkey Creek drainage and the western upper portion of the Silver Peak drainage both experienced fire covering approximately 29 square miles with elevations ranging from 9300' to 5400' at Paradise.  Increased runoff would be expected in east flowing stream beds within the 66 square miles encompassed by these 2 drainage's.

Nine drainage's (blue) with Horseshoe Two fir perimeter (red).

Flys Peak, Chiricahua Peak, and South Fork drainage's have a combined surface area of 68.2 square miles with elevations ranging from  9759' at Chiricahua Peak down to 4800' at Portal.  Of these 3 drainage's approximately half of the South Fork drainage (eastern half) was unburned.  These 3 drainage's as well as the Silver Peak drainage contribute to the flow of Cave Creek.  Based on the fire perimeter and the drainage's that contribute to Cave Creek, approximately 50 square miles were affected by fire.  Runoff from affected areas in these 4 drainage's can be expected to contribute to increased flow in Cave Creek during the monsoon season.

The 50 square miles of the combined Cave Creek drainage affected by fire (white line).

Sulphur Canyon drainage is an isolated triangular drainage of 12.5 square miles that flows out of the east side of the Chiricahua Mountains with a maximum elevation of 8500' at Portal Peak and 4700' at the forest boundary.  The relatively small size of the Sulphur Canyon drainage, relative to Cave Creek, suggests Sulphur Canyon would experience a smaller amount of uncontrolled runoff which would dissipate as the flow spreads across the San Simon valley.

Horseshoe Canyon drainage at 40.5 square miles was the largest single drainage mapped.  This drainage has a north south orientation along its first half then turns east to flow out into the valley.  It ranges in elevation from over 8800' down to 4600' at the canyon mouth.  The large size of this drainage suggests it could experience significant flow during the monsoon well in excess of normal monsoon flows.

The last drainage mapped was Price Canyon.  This drainage starts in the interior of the Chiricahua Mountains at elevations of approximately 9200' ranging down to 5500' at the canyon mouth.  It is a relatively narrow drainage with a north south orientation encompassing 22.5 square miles.  The moderate size of the drainage combined with the elevation change suggests an intermediate volume of monsoon flow in Price Canyon.

The intensity of the fire across the landscape is yet unknown and large areas of relatively low burn could mitigate monsoon runoff, but assuming a uniform burn, it is predicted that Cave Creek and Horseshoe Canyons would experience the highest levels of runoff, followed by Turkey Creek and Price Canyon.  Finally, Sulphur Canyon would experience the smallest runoffs of those drainage's mapped.

While mitigation efforts are underway with chipping of felled trees and rehabilitation of fire lines the major effort will begin after containment.  From the BAER team:
"The primary techniques used are reseeding of ground cover with quick-growing or native species;mulching with straw or chipped wood; constructing straw bale dams in small tributaries; placing fallen trees to catch sediments on steep slopes; and digging below-grade pits to catch runoff and store sediments."