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Impact of different parts of unpaved forest roads on runoff and sediment yield in a Mediterranean area

Jordán-López, Antonio, Martínez-Zavala, Lorena, Bellinfante, Nicolás
Science of the total environment 2009 v.407 no.2 pp. 937-944
forest roads, runoff, sediment yield, rainfall simulation, water erosion, Spain
Surface runoff and sediment production on unpaved forest roads in a humid Mediterranean mountainous area has been studied using a simple portable rainfall simulator at an intensity of 90 mm h⁻¹. Thirty six rainfall simulations were carried out on road plots: on the roadbank (12), on the sidecast fill (12), and on the roadbed (12). On the roadbanks, the steady-state runoff coefficient was 85.9% and runoff flow appeared after 63 s on average. On the sidecast fills, the steady-state runoff coefficient was 58.6% and mean time to runoff was 48 s. Finally, on the roadbeds, the steady-state runoff coefficient was 21.5% and mean time to runoff was 41 s. The highest soil loss rate was found on the roadbanks (486.7 g m⁻²), mainly due to low plant cover, soil texture and rock fragments. The total soil erosion on the roadbanks was 3 and 18 times higher than those from the roadbeds and the sidecast fills, respectively. As a consequence, roadbanks can be considered the main source of sediments on the studied sites, but the function of unpaved forest roads as source points for runoff generation is more important.