Unpaved rural roads as source areas of sediment in a watershed of the Brazilian semi-arid region |
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| Institution: | 1. Federal Institute of Education, Science and Technology of Ceará, Fortaleza, Brazil;2. University of Valladolid, Campus La Yutera, Palencia, Spain;3. Federal University of Ceará, Department of Agricultural Engineering, Campus do Pici, Bloco 804, 60.450-760, Fortaleza, Brazil;1. Deltares, Boussinesqweg 1, 2629 HV Delft, The Netherlands;2. U.S. Army Engineer Research and Development Center, 3909 Halls Ferry Road, Vicksburg, MS 39180, USA;3. Ghent University, Technologiepark 68 905, B-9052 Zwijnaarde, Belgium;4. Leovanrijn-Sediment-Consultancy, Domineeswal 6, 8356 DS Blokzijl, The Netherlands;1. Department of Civil Engineering, Stellenbosch University, Stellenbosch, South Africa;2. Christian-Doppler Laboratory for Multi-scale Modelling of Multiphase Processes, Johannes Kepler University, Austria;1. Department of Civil & Environmental Engineering, 941 rue Charles Bourseul, BP 10838, 59508 Douai, France;2. Toulouse University, Mines Albi, CNRS, RAPSODEE Center, Campus Jarlard, F-81013 Albi cedex 09, France;3. SOLVAY SA, DCRT, rue de Ransbeek 310, B-1120 Bruxelles, Germany;4. PRAYON SA, rue J. Wauters, Engis, Belgium;1. Instituto de Mecánica de los Fluidos e Ingeniería Ambiental, Facultad de Ingeniería, Universidad de la República, J. Herrera y Reissig 565, CP 11300 Montevideo, Uruguay;2. Université Paris-Est, Laboratory for Hydraulics Saint-Venant (ENPC-EDF/R&D-CEREMA), 6 quai Watier, BP 49, 78401 Chatou Cedex, France;3. Electricity of France, R&D Department, 6 quai Watier, BP 49, 78401 Chatou Cedex, France;4. Sorbonne Universités, Université de Technologie de Compiègne, FRE UTC-CNRS 3023, Roberval, Centre de Recherche Royallieu, CS 60 319, 60203 Compiègne Cedex, France;5. Cerema, Direction Technique Eau, Mer et Fleuves, 134 rue de Beauvais, CS 60039, 60280 Margny Lès Compiègne, France;6. Institut National de la Recherche Scientifique, Centre - Eau Terre Environnement, 490 Rue de la Couronne, Québec, Canadá G1K 9A9;1. College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing 210098, China;2. Kunming Engineering Corporation Limited, Kunming 650041, China |
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| Abstract: | Approximately 80% of the road network in Brazil is unpaved and shows evidences of a high erosion potential. In the semi-arid Caatinga Biome in the northeast of the country, a monitoring programme has been done for two years in order to analyze runoff and sediment production from unpaved rural roadways and from embankments. Sediment production ranged from 0.30 to 0.92 Mg/ha yr, higher than in undisturbed areas, but generally lower than that reported for unpaved roads in other regions. However, this is a semi-arid area with low rainfall and runoff and, hence, with a limited hydrological connectivity and sediment production. Sediment production on an embankment with no vegetation was around ten times higher than on an embankment with vegetation. On the road surface, annual sediment production (normalized for gradient) in a section with traffic was three times higher than for a road surface without traffic. In addition, events that occurred after roadway maintenance activities generated peaks of sediment concentration of over 5000 mg/L. These results suggest that sediment production from roads and embankments with bare surfaces is at least one order of magnitude higher than in undisturbed catchment areas. Maintenance activity and vehicle traffic contribute to an increase in sediment availability and impact on the sediment concentration, but less intensely on sediment loads, which depend on the runoff magnitude of the events occurring after roadway maintenance. It was also found that the natural vegetation of the semi-arid region potentially captures sediment on roadway embankments; thereby playing an important role in breaking connectivity between the sediment flow from unpaved roads and the natural drainage system of the catchment. |
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| Keywords: | Sediment production Caatinga vegetation Road maintenance Embankment |
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