期刊
LAND DEGRADATION & DEVELOPMENT
卷 27, 期 2, 页码 179-189出版社
WILEY
DOI: 10.1002/ldr.2294
关键词
braided channel; channel incision; land use changes; deforestation; reforestation; debris flows; central Pyrenees
资金
- project INDICA - Spanish Ministry of Economy and Competitiveness [CGL2011-27753-C02-01, CGL2011-27753-C02-02]
- project HIDROCAES - Spanish Ministry of Economy and Competitiveness [CGL2011-27574-C02-C01]
- Aragon Government
- European Social Fund (ESF-FSE)
- Spanish Ministry of Economy and Competitiveness
Channel changes are the consequence of changes in sediment yield from the slopes and in the connectivity between slopes and channels because of distinct land use and climate impacts. In this study, we investigated the characteristics and evolution of a short reach in the headwater of the Ijuez River, central-southern Pyrenees. Assessment of a series of sedimentary and geomorphic structures confirmed major changes to the valley bottom, mainly related to changes in the intensity of human activity. The oldest sedimentary structure is a terrace level located 3 to 4m above the current alluvial plain. General deforestation, overgrazing and recurring fires in the montane belt (1100-1600ma.s.l.) have led to increased soil erosion and connectivity, and to the triggering of debris flows that have been deposited on the fluvial terrace. Woody fragments from within the debris flows were dated using accelerator mass spectrometry C-14 radiocarbon techniques (AMS), yielding ages between 100 and 115cal years bp, which coincides with the period of maximum deforestation and human density in the Pyrenees. Depopulation and farmland abandonment since the beginning of the 20th century has resulted in generalized natural and artificial reforestation, a shrinkage of the eroded areas and a decline in connectivity between slopes and the channel. The most important consequence has been channel incision and narrowing, and the development of a sediment armour layer. Active sediment transport is continuing, although there has been a decrease in sediment yield from the slopes. Copyright (c) 2014 John Wiley & Sons, Ltd.
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