Silica sand slope gullying and mining in Central Spain: Erosion processes and geomorphic reclamation of contour mining

Abstract

A characterization and quantification of the geomorphic activity of three scenarios of silica sand slopes of Central Spain (Segovia and Guadalajara province), is being carried out: (a) silica sand slope gullies; (b) non-reclaimed (abandoned) silica sand mines; (c) abandoned silica sand mines reclaimed with a geomorphic approach. On the silica sand slope gullies, gathered data point at very high rates of erosion and sedimentation, since runoff and hydric erosion occurs on them almost instantaneously after precipitation. When no reclamation is made, silica sand mines evolve like natural gullies, and they show higher rates of hydric erosion than them. The erosion of non-reclaimed silica sand mines produces severe on and off site environmental impacts. When reclamations are made based on geomorphic approaches, runoff and soil erosion can be reduced to the minimum at the pediment areas, whereas the highwalls can maintain a geomorphic activity which integrates them into the landscape. The understanding of these scenarios is allowing improving new reclamation plans on silica sand and kaolin mines of Central Spain, concerning their topographical and watershed design, and layout of the reconstructed terrain (waste dumps, surficial deposits, and topsoil). The latter example shows a desirable framework of collaboration between mining companies, protected areas managers and universities.