Water runoff from road surface in mountain forests

Abstract

Forest roads are treeless strips of land without any natural cover, appropriately shaped in a longitudinal and transverse direction, along which traffic is possible. Road embankments and surfaces are made of proper materials, with the preservation of technological requirements and particular attention to the density of subbases in the road construction. Surface water runoff occurs on all roads as a result of rainfall, because material density of the surface hinders or blocks the infiltration and the road gradient causes the water movement. Precipitation intensity and ground filtration capacity determine the runoff quantity. In forest areas, the surface runoff basically occurs on road surfaces and timber depots, while outside those sites, it rarely occurs in natural and not devastated areas. The paper presents the results of measurements of the surface-runoff intensity from forest dirt roads along several surveyed sections. Some sections were characterised by a high escarpment of the excavation and cross-cut canal for subsurface runoff. The unit intensity from measurement sessions of various precipitation levels was presented, as well as those from the period of snow cover melting. Measurements were taken every 15 minutes. On the basis of these measurements, simulation calculations of the amount of water were performed assuming the homogeneity of the area, the road network and precipitation characteristics, which can occur in the form of surface runoff on forest roads with similar characteristics, in the area of 100 ha, with the road network density of 15 m·ha-1 and 25 m·ha-1, during the precipitation lasting 3 h. These values were referred to the total water quantity from such precipitation and compared with the standard water consumption by an average consumer.