Historical geomorphological processes and its relationship to the human activity in central pyrenees (spain)

Abstract

The Central Spanish Pyrenees show a great diversity of geomorphic processes in relation with topographic and climatic heterogeneity and according to the strong altitudinal gradient. Human activity in the last millenniums has contributed to disturb the original landscape and its hydromorphological dynamics: the upper forest belt was eliminated by means of Jire during the Middle Age, in order to enlarge the extent of summer pastures; and the hillslopes located under 1600 m were cultivated in heavy topographic conditions, being frequently burnt in order to improve the quality of pastures. At present, evidences of this human activity are visible everywhere; in the subalpine belt mass movements and dense rill networks caused the loss of many soils and the expansion of gelifluxion terracettes; in middle mountain, overland flow has much increased the soil surface stoniness, and debris flows of different size have developed on the hillslopes and on the river channels. Rivers show a strong torrentiality, prevailing unstable channels and coarse sediment transport. The authors apport information on some historical geomorphic processes, related with human activity.