This paper presents the history of badland generated in the Saldaña region, Spain; as well as the main responses eight decades after the start of restorationin terms of vegetation, soil and erosive processes. The restoration consisted of intense reforestation and construction of more than 100 check dams and numerous wattle fences. Presently, the dense vegetation (87% cover) contrasts markedly with the degraded landscape from the early 20th century (5% cover). The thickness of litter and the natural presence of some species (Quercus pyrenaica, Paeonia broteroi and Lactarius deliciosus) clearly indicate the recovery of the site. The development of the forest cover shows that the intervention has the potential to recover almost 90% of the area. There is also evidence of soil regeneration, although some properties (erodibility, resistance to penetration and shear-strength resistance) are not that different between the forested and degraded areas. In the restored zones, runoff is negligible, since a thick layer of moss covers the spillways of all the check dams. Erosion has almost been stopped by the effects of vegetation cover, litter and higher infiltration rates (infiltration rate in forested slopes is 43.4 times greater than in bare slopes). Sediment detachment, such as landslides, mudflows and piping, still occur, but are restricted to the degraded zones. Furthermore, even when sediments are mobilized from the upper degraded hillslopes during the larger storms events (2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010), check dams and the lower elevation restored forest-buffers effectively work to reduce the sediment yield into the Carrión River by almost three orders of magnitude (<10 2 mg L -1 ), compared with data from the 1930s and 1940s (>10 5 mg L -1 ). Ayerbe (1930) wrote that the land was almost bare; b Azcarretazábal (1963) made one list with the species from the badlands; c from the Martínez de Azagra et al. (1997) inventory and our fieldwork; d because it was not fully grown at the time of our observations. 1568J. NAVARRO HEVIA ET AL.

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Check dams play an important role worldwide in sediment retention, although their effectiveness is currently the subject of debate. In this study, 11 geometric models with their field methodology and equations are proposed to estimate the retained sediment quickly, easily and with a sufficient degree of approximation. The models were applied to a sample of check dams in the Saldaña badlands (Spain) in accordance with the shape of the valley to determine the volume of retained sediment and compare them with other widely used methods. Our geometric method gave lower volumes than topographic methods, but higher volumes than simple methods. This method is thus useful as a first approximation to estimate the sediment trapped by check dams and small silted dams, minimizing fieldwork, calculations and cost. Furthermore, it allows the selection of a better fit to the sediment wedge shape and higher accuracy than the simple methods used until now.

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