Agricultural straw, hydromulch, and wood shred or wood strand mulches increasingly are being used as post-fire hillslope treatments, but the differences in effectiveness among these mulch treatments are not fully understood. Following the 2002 Hayman fire in central Colorado and the 2003 Cedar fire in southern California, matched catchments were monitored for five to seven post-fire years to determine the effectiveness of wheat straw mulch (Hayman fire only) and hydromulch in reducing post-fire runoff, peak flow rates, and sediment yields from natural rainfall. Measured runoff and sediment yields were caused by short duration high intensity summer storms at the Hayman fire and long duration winter rains at the Cedar fire. The wheat straw mulch treatment significantly reduced peak flow rates and sediment yields at the Hayman fire. The annual peak flow rates in the first two post-fire years in the straw mulch catchment were 4.5 and 3.9 m3 s-1 km-2 (respectively) as compared to 4.3 and 7.1 m3 s-1 km-2 (respectively) in the control. In post-fire years one and two, the maximum event sediment yields in the straw mulch catchment were 7.2 and 10 Mg ha-1, respectively, which were less than half of the maximum event sediment yields in the control catchment (19 and 24 Mg ha-1, respectively). The straw mulch catchment had no detectable runoff or sediment yield after the second post-fire year, but the control catchment continued to have measurable runoff and sediment yields through the seventh post-fire year. The straw mulch treatment effect in runoff reduction was not significant in the statistical model. Total ground cover was 80% immediately after the application of straw mulch, and decreased to 10% by the end of first post-fire year, yet total ground cover values remained high as litter and vegetation, including invasive cheatgrass, increased.
Robichaud, Peter R.; Wagenbrenner, Joseph W.; Lewis, Sarah A.; Ashmun, Louise E.; Brown, Robert E.; Wohlgemuth, Peter M. 2013. Post-fire mulching for runoff and erosion mitigation; Part II: Effectiveness in reducing runoff and sediment yields from small catchments. Catena. 105: 93-111.