Hydroseeding

Abstract: A series of 75 non-bordered plots was used to measure surface erosion on granitic road cuts on forest roads in the mountains of Idaho. Erosion data were collected for four years following road construction. Erosion rates for the first winter period after construction averaged about five times greater than the average of erosion rates for subsequent seasons. Both mass and surface erosion processes were observed on road cuts with mass erosion particularly important during the first season after construction. Regression analysis showed slope gradient, slope aspect, ground cover density and snow-free period rainfall erosivity had statistically significant effects on erosion. Slope gradient was by far the most influential site factor affecting erosion but slope length had no affect. Three erosion control treatments – dry seeding, hydroseeding plus mulch, and terracing with hydroseeding plus mulch – were evaluated. Two treatments – dry seeding and hydroseeding plus mulch –caused statistically significant reductions in erosion. Dry seeding was the most cost-effective treatment on sites with deep alluvial soil. Elsewhere, hydromulching was the most cost-effective treatment. Further testing is needed to evaluate the effectiveness of erosion control treatments during the first period after construction. We were unable to discriminate between erosion rates on the moderately to highly weathered granitic rock included in this study. A discussion of the application of the study results is presented. Copyright © 2001 John Wiley & Sons, Ltd.

Abstract: This synthesis of post-fire treatment effectiveness reviews the past decade of research, monitoring, and product development related to post-fire hillslope emergency stabilization treatments, including erosion barriers, mulching, chemical soil treatments, and combinations of these treatments. In the past ten years, erosion barrier treatments (contour-felled logs and straw wattles) have declined in use and are now rarely applied as a post-fire hillslope treatment. In contrast, dry mulch treatments (agricultural straw, wood strands, wood shreds, etc.) have quickly gained acceptance as effective, though somewhat expensive, post-fire hillslope stabilization treatments and are frequently recommended when values-at-risk warrant protection. This change has been motivated by research that shows the proportion of exposed mineral soil (or conversely, the proportion of ground cover) to be the primary treatment factor controlling post-fire hillslope erosion. Erosion barrier treatments provide little ground cover and have been shown to be less effective than mulch, especially during short-duration, high intensity rainfall events. In addition, innovative options for producing and applying mulch materials have adapted these materials for use on large burned areas that are inaccessible by road. Although longer-term studies on mulch treatment effectiveness are on-going, early results and short-term studies have shown that dry mulches can be highly effective in reducing post-fire runoff and erosion. Hydromulches have been used after some fires, but they have been less effective than dry mulches in stabilizing burned hillslopes and generally decompose or degrade within a year.

Abstract: article 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 effective- ness 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 dura- tion 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 m 3 s −1 km −2 (respectively) as compared to 4.3 and 7.1 m 3 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 con- trol 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 run- off and sediment yields through the seventh post-fire year. The straw mulch treatment effect in runoff reduc- tion 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. The hydromulch cover at both fires declined rapidly and provided less than 10% of the ground cover within 2.5 months after application at which point the catchment was presumed to be untreated. Due to differences in precipitation, the three catchments at the Cedar fire had significantly different hydrologic responses during the presumed untreated portion of the study, which precluded evaluation of treatment effectiveness during the short treated period. The peak flow responses from the hydromulch and control catchments at the Hayman fire were also different during the presumed untreated period and were not tested. Although the runoff and sediment yields did not differ during the presumed untreated period and were tested for treat- ment effects, the Hayman hydromulch treatment did not significantly affect either response during the first post-fire year—the presumed treated period. Unit-area sediment yields from the catchments were similar to those measured on hillslope plots at both the Hayman and Cedar fires in the first post-fire years, but in later years the sediment yields from the catchments were at least double the sediment yields measured on hillslope plots. The longer periods of greater erosion rates in the catchments likely reflect the addition of channel erosion processes and a difference in hydrologic connectivity at the catchment scale. Published by Elsevier B.V.