Title: The effectiveness of aerial hydromulch as an erosion control treatment in burned chaparral watersheds
Author: Wohlgemuth, Pete; Beyers, Jan; Robichaud, Pete
Source: In: Medley, Nicolas; Patterson, Glenn; Parker, Melanie J., eds. 2011. Observing, studying, and managing for change—Proceedings of the Fourth Interagency Conference on Research in the Watersheds. Scientific Investigations Report 2011-5169. Reston, VA: U.S. Geological Survey. pp. 162-167
Description: High severity wildfire can make watersheds susceptible to accelerated erosion, which impedes resource recovery and threatens life, property, and infrastructure in downstream human communities. Land managers often use mitigation measures on the burned hillside slopes to reduce postfire sediment fluxes. Hydromulch, a slurry of paper or wood fiber that dries to a permeable crust, is a relatively new erosion control treatment. Delivered by helicopter, aerial hydromulch has not been rigorously field tested in wildland settings. Concerns have been raised over its ability to reduce watershed erosion along with its potential for negative effects on postfire ecosystem recovery. Since 2007 we have compared sediment fluxes and vegetation regrowth on plots treated with aerial hydromulch versus untreated controls for three wildfires in southern California. The study plots were all on steep slopes with coarse-textured soils that had been previously covered with mixed chaparral. Sediment production was measured with barrier fences that trapped the eroded sediment. Surface cover was repeatedly measured on meter-square quadrats. The aerial hydromulch treatment did reduce bare ground, and at least some of this cover persisted through the first postfire winter rainy season. Aerial hydromulch reduced hillslope erosion from small and medium rainstorms (peak 10-minute intensities of <30 mm/hr), but not during an extreme high-intensity rain event (peak 10-minute intensity of >70 mm/hr). Hydromulch had no effect on regrowing plant cover, shrub seedling density, or species richness. Hence, in chaparral watersheds, aerial hydromulch can be an effective postfire erosion control measure that is environmentally benign with respect to vegetation regrowth.
Keywords: wildfire, erosion control, hydromulch
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Wohlgemuth, P.M.; Beyers, J.L.; Robichaud, P.R. 2011. The effectiveness of aerial hydromulch as an erosion control treatment in burned chaparral watersheds. In: Medley, Nicolas; Patterson, Glenn; Parker, Melanie J., eds. 2011. Observing, studying, and managing for change—Proceedings of the Fourth Interagency Conference on Research in the Watersheds. Scientific Investigations Report 2011-5169. Reston, VA: U.S. Geological Survey. pp. 162-167
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