O impacto do carreamento de solo na drenagem pluvial de vias pavimentadas: análise prática e por ferramentas de previsão à erosão

Abstract

The road system is essential for the development of a country, used daily for the movement of loads and people. In Brazil, more than 70% of the roads are not paved, bringing impacts such as the increase of particulate matter in the atmosphere and soil erosion. Although there are studies that correlate the impact of erosion and soil carryover in rural and forest areas, no studies were found that associate the erosion damage of unpaved roads and areas around paved roads and rainwater galleries. In urban areas, storm drainage systems are built to drain surface water, but when poorly designed or overloaded, they cause flooding. In this way, the storm drainage of paved roads ends up suffering from the carry-over of soil derived from unpaved roads. With this, the objective of the present work was to analyze the impact of soil carry-over from unpaved streets in the storm drainage of paved streets. There was a practical analysis with the construction and installation of a sediment collector inside the storm drain for a period of six months, every ten days or every precipitation (>5mm), measured from a rain gauge installed near the analysis section. The collector was removed and the sediment was weighed. From the same soil, a granulometric test was carried out. As tools for predicting erosion, the Universal Soil Loss Equation (USLE) and the FSWEPP software, developed by the US Department of Forestry Services, were chosen. This study demonstrated that the soil used in unpaved streets is environmentally unsuitable, due to its high rate of erodibility and sedimentation, with a tendency to accelerate the silting up of storm water. In addition, it was found that an unpaved road can carry about 3.99 kg.m-2.year-1 of soil to storm water, which is 4 to 20 times greater than in places with only paved roads. In an estimation, it was found that portion of land can impact over 19 meters of storm water per year. Therefore, it can be seen that erosion and soil carry-over from unpaved roads has serious consequences for the storm drainage gallery. The USLE equation overestimated the result by almost five times that found in the field (14.16 kg.m-2.year-1 compared to 3.99 kg.m-2.year-1), not being the most adequate to estimate the erosion of unpaved roads. On the other hand, the computational model indicated a value of 2.38kg.m-2.year-1, close to that found in the field work, but with the need for adjustment for the location. Therefore, it can be seen that erosion and soil carry-over from unpaved roads has serious consequences for rainwater drainage from paved roads, causing accelerated silting of the system, a situation not foreseen in norms and construction projects. Even só, studies should be deepened for other regions of the country, in addition to the need to develop new erosion containment systems and Sustainable Rainwater Drainage Systems.