Abstract
This paper presents a new methodology to assess sediment connectivity at the catchment scale. The proposed index CCI (Catchment Connectivity Index) is based on a combination of factors in a GIS environment that determine the connectivity of sediment in different elements (slopes, basins, channels) of the river system. The factors evaluated are the transport capacity on hillslopes (TC), check-dams’ trap efficiency (TE), the presence of geomorphological barriers (GF), flow conditions (FC) and the sediment transport capacity in channels (SP). This index was applied to estimate connectivity in the Upper Taibilla catchment (314 km2) (SE Spain) for different land use (1956 and 2006) and management (check-dams) scenarios. This catchment has suffered major land use and land cover changes over the last 50 years. The intense agricultural abandonment process and the implementation of soil erosion control measures (reforestation and check-dams) have strongly affected sediment dynamics of the basin. Calculation of the CCI allows identifying which landscape elements have most impact on the sediment (dis)connectivity at catchment scale. The results show a significant reduction in the connectivity of 76% between 1956 and 2006. However, it is observed that the check-dams contribute only 3% to this reduction. Land use changes had a much higher impact on reducing sediment connectivity, except in some areas with steep slopes, or with the development of agriculture along the main channels of the drainage network. Altogether, CCI showed to be a relatively easy and effective method that can be used for spatio-temporal sediment connectivity analyses in areas with natural and human disturbances.
Highlights
Palabras clave: erosión del suelo, modelización, redistribución de carbono, dique de retención, cuenca
Results from various studies published during the last decades suggest that soil erosion could be playing an important role in the global carbon (C) cycle
One of the major uncertainties is related to the effect that lateral fluxes of sediment and C may have on soil C dynamics and on its distribution within the landscape
Summary
Los procesos de erosión hídrica inducen la movilización de carbono orgánico del suelo (SOC) a través de flujos laterales de carbono (C) (redistribución en superficie) y flujos verticales de C (intercambio de C entre la atmósfera y el suelo a través de procesos de mineralización o secuestro de C). En la actualidad se estima que la combinación de flujos laterales y verticales de C inducidos por la erosión, puede tener un impacto significativo sobre el balance global de C como resultado de la interacción de varios procesos (Berhe et al, 2007; Van Oost et al, 2007). La modelización es una buena herramienta para simular los flujos de carbono orgánico inducidos por erosión y ayudar a la evaluar la importancia de los mismos en el marco de la escala de cuenca, donde determinadas clases y patrones de cobertura vegetal y uso del suelo interactúan en la dinámica erosiva y deposicional. SPEROS-C combina la redistribución de suelo por erosión hídrica y por laboreo (Van Oost et al, 2003) con el modelo ICBM de balance de carbono (Introductory Carbon Balance Model) (Andrén y Kätterer, 1997), que simula flujos verticales de C dentro del perfil del suelo. Para ello se tienen en cuenta tanto datos obtenidos con la aplicación del modelo como resultados de otros estudios
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