Evaluating the Effectiveness of Mulching for Reducing Soil Erosion in Cut Slope and Fill Slope of Forest Roads in Hyrcanian Forests

Abstract

Forest operations often enhance runoff and soil loss in roads and skid trails, where cut slopes and fill slopes are the most important source of sediment. This study evaluated the effectiveness of four erosion control treatments applied to cut slope and fill slope segments of forest roads of different ages in the Hyrcanian forest in northern Iran. The treatment combinations, each replicated three times, included four classes of mulch cover (bare soil [BS], wood chips cover [WCH], sawdust cover [SC], and rice straw cover [RSC]), two levels of side slope (cut slope and fill slope), two levels of side slope gradient (20–25% and 40–45%), and three levels of road age (three, 10 and 20 years after construction). Mulch cover treatments significantly reduced average surface runoff volume and sediment yield compared to BS. Regardless of erosion control treatment, greater surface runoff volume and soil loss under natural rainfall occurred on steeper slope gradients in all road age classes and decreased with increasing road age on both slope gradients. On cut slopes, average runoff and soil loss from the plots covered with WCH (17.63 l per plot, 2.43 g m–2) was lower than from those covered with SC (22.81 l per plot, 3.50 g m–2), which was lower than from those covered with RSC (29.13 l per plot, 4.41 g m–2 and BS (34.61 l per plot, 4.94 g m–2). On fill slopes, average runoff and soil loss from the plots covered with WCH (14.13 l per plot, 1.99 g m–2) was lower than from plots covered with SC (20.01 l per plot, 3.23 g m–2), which was lower than from plots covered with RSC (24.52 l per plot, 4.06 g m–2) and BS (29.03 l per plot, 4.47 g m–2). Surface cover successfully controlled erosion losses following road construction, particularly on steep side slopes with high erosion potential.

Spatial-temporal Analysis of Soil Erosion Based on Spatial Model and GIS Technology

“…This method is unrealistic for large-scale research scales. With the development of GIS technology, at present, the slope and slope length are mainly obtained through DEM data, and then the slope formula used by domestic researchers can be used to calculate LS [14][15].…”

A Review of the Sediment Production and Transport Processes of Forest Road Erosion

“…x FOR PEER REVIEW 4 of 20 Road fill slopes are commonly constructed on the sides of road embankments with specific slopes to ensure roadbed stability [36]. However, the loose nature of the materials used in embankments makes them susceptible to soil erosion and landslides, which contribute significantly to sediment in road erosion [37]. As erosion progresses and gullies form, road fill slopes or the lower hillslopes may directly or indirectly connect to streams [38], intensifying the transport of eroded sediment from the road surface or cut slope to the stream [10,39].…”

A hot-spot analysis of forest roads based on soil erosion and sediment in Zagros forest lands, Iran

“…As the height of the excavation trench increases, the amount of sedimentation from these areas also increases due to soil creeping and washing into nearby waterway channels (Burroughs and King 1989). However, accurately measuring this factor can be challenging and may be impossible in some areas (Solgi et al 2021).…”