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ARS Home » Pacific West Area » Boise, Idaho » Northwest Watershed Research Center » Research » Publications at this Location » Publication #214058

Title: Measuring effectiveness of three postfire hillslope erosion barrier treatments, Western Montana, USA

item Pierson, Fred

Submitted to: Hydrological Processes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/7/2007
Publication Date: 12/3/2008
Citation: Robichaud, P.R., Pierson Jr, F.B., Brown, R.E., and Wagenbrenner, J.W. 2008. Measuring Effectiveness of Three Postfire Hillslope Erosion Barrier Treatments, Western Montana, USA. Hydrological Processes 22:159-170.

Interpretive Summary: After wildfire, landscape treatments are often applies to mitigate potential increases in runoff and erosion. Simulated and natural rainfall events were used to compare the effectiveness of contour-felled logs, straw wattles and hand-dug trenches for reducing erosion from burned hillslopes. The logs and wattles were more effctive than the trenches which were of little impact compared the untreated control. During large rainstorms, runoff and sediment were observed going over the top and around the end of barriers even when the barriers were less than half filled.

Technical Abstract: After the Valley Complex Fire burned 86000ha in western Montana in 2000, two studies were conducted to determine the effectiveness of contour-felled log, straw wattle, and hand-dug contour tench erosion barriers installed in mitigating postfire runoff and erosion. Sixteen plots were located across a steep, severly burned slope, with a single barrier installed in 12 plots (four per treatment) and four plots left untreated as controls. In a rainfall-plus-inflow simulation, 26 mm h rainfall was applied to each plot for 1 h and 48 L min of overland flow was dded for the last 15min. Total runoff from the contour-felled log plots (1-3 mm) showed no difference. The total sedminet yield from the straw wattle plots (.21 Mg ha) was significantly less than the control plots (2-2 Mg ha); the sediment yields in teh contour-felled log plots (.58 Mg ha) and the contour trench plots (2.5 Mg ha) were not significantly different. After the simulations, sediment fences were installed to trap sediment eroded by natural rainfall. During the subsequent 3 years, sediment yields from individual events increased significantly with increasing 10 min maximum intensity and rainfall amounts. High-intensity rainfall occurred early in the study and the erosion barriers were filled with sediment. There were no significant differences in event or annual sediment yields among treated and control plots. In 2001, the overall mean annual sediment yield was 21 Mg ha; this value declined significantly to .6 Mg ha in 2002 and .2 Mg ha in 2003. The erosion barrier sediment storage used was less than the total available storage capacity; runoff abd sediment were observed going over the top and around the ends of the barriers even when the barriers were less than half filled.