Wildfire, Rain and Floods: A case study of the June 2010 Schultz Wildfire, Flagstaff, Arizona
Additional BAER Treatments
A second BAER rapid assessment of July 29th, 2010, evaluated the impacts of the July 20th flood event. Four additional treatments were recommended and implemented in August 2010. These treatments included aerial seeding with a blend of native grasses and non-persistent annuals, applying straw mulch in select areas, removing log-debris jams in two drainages, and constructing waterbars and drains on 23 miles of Forest roads.
A third round of BAER funding was made available in October 2010. By October 29th select areas were reseeded with mix of native grasses and barley (a non-native annual), intended to "jumpstart" native regeneration and reduce erosion in 2011. Another application of mulch with weed-free straw was complete November 7th. Areas with slopes greater than 40% required a second application of seed and mulch to replace materials lost to wind or water.
The series of BAER treatments qualify as emergency stabilization. Recent research by Robichaud and others (2010) has shown that straw mulch applied on slopes <60% is effective at stabilizing slopes and inhibiting rill and gully development. However, treatments on the low to moderate slopes have had very little impact on flooding and sediment movement in the Shultz fire area because of the concentration of high-severity burn on steep mountain slopes. On these slopes, the efficacy of straw mulch and seed applications for mitigating runoff and erosion is questionable because these treatments are susceptible to removal by surface runoff or wind (Robichaud and others, 2010).
Within the Schultz Fire burn area, debris flows and high energy flood flows originate high in the watersheds on the extremely steep and severely burned slopes of the San Francisco Peaks. In the upper-basins around FR146 straw mulch washed down the hillslopes resulting in the need for re-applications of mulch. Based on our observations, over half of the straw mulch applied to the steep slopes of the Schulz Fire has been removed by surface runoff and wind. Nonetheless, multiple straw mulch and seed applications were made to aid in the reduction of runoff and soil erosion during the summer and fall of 2010. By using the winter snowpack to stabilize the straw mulch and seeds, runoff and erosion should be reduced further in 2011.
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