Efectos de las extracciones de áridos sobre el transporte de sedimentos en suspensión en ríos de montaña (alto río Cinca, Pirineo Central)

Abstract

This paper examines the effects of gravel mining on the suspended sediment transport in the Upper River Cinca (Central Pyrenees). Discharge, sediment transport and sediment grain-size distribution were measured, sampled and further determined in five monitoring sections along a 5-km river reach. Samples were taken at a section upstream from the mined area (i.e. reference section) and in four sections downstream (0, 200, 500 and 1500 meters). The results show that sediment concentrations downstream from the target site were up to one order of magnitude higher than in the reference section. Average concentrations during the impact were similar to those observed during floods, with maximum values attaining 6 g/l. Total load ranged from 2.2 to 17 Mg/day between sections; these values include the effects of the earth-moving works performed before the mining started. Concentrations at the lowermost section of the study reach were similar to those observed at the upstream reference section, suggesting that most of the suspended material was deposited in the channel. The transported material was coarse than that sampled under reference conditions; nevertheless, largest particles settled quickly, suggesting a selective transport downstream. This study constitutes a first step towards a better understanding of local sediment dynamics in rivers affected by maintenance works and related activities, such as gravel mining, and, overall, supports the comprehensive assessment of the effects of human actions on channel morphodynamics and the ecological functioning of mountain fluvial systems.

Dynamic changes in the lower Gállego River (Ebro Basin, NE Spain) and their relationship with anthropic activities and the quaternary substrate

“…Among them, they cite sediment deficit, rupture of the equilibrium between sediment supply and transport capacity, riverbed armoring, loss of lateral channel mobility with a tendency to develop one straight and unstable channel, and upstream and downstream erosion. The same effects have been described for the rivers in NE Spain (Batalla, 2003;Rovira et al, 2005;Tuset et al, 2015;Béjar et al, 2018;Muñoz-Narciso et al, 2018) and by Martín-Vide et al (2010) for the lower Gállego. Other effects have been mentioned for flora and fauna and water quality in general, both during gravel mining and after this activity ceased (Meador and Layher, 1998;Buendía et al, 2011;Jones et al, 2012;Béjar et al, 2017).…”

“…Therefore, an estimation of the volumes of extracted and eroded gravel would be unrealistic. Béjar et al (2018) analyzed the mining effects on the riverbed during gravel mining in another Pyrenean river (the Cinca River) and found that the sediment volume transported downstream was similar to that generated by a flood and smaller in the case of solid lode. They also indicated that these mining activities affect up to 1.5 km downstream.…”

Análisis multi-temporal de los cambios geomorfológicos y de la cubierta vegetal en un cauce extenso de gravas: el río Cinca, Aragón (España)

“…(Brierley & Fryirs, 2005), también han sido objeto de estudio en casos muy significativos. Así, la pérdida del modelo o estilo trenzado en muchos ríos europeos ha sido puesta de relieve en numerosos trabajos(Bravard & Peiry, 1993;Surian & Rinaldi, 2003;Piégay et al, 2009), llegando a considerarse un estilo geomorfológico en peligro de extinción(Montgomery & Bolton, 2003;Wohl, 2006Wohl, , 2019.En el presente trabajo se ha seleccionado un tramo del río Cinca, afluente del río Ebro que discurre por el Pirineo y Prepirineo aragonés oriental, que ha sido objeto de estudio de numerosos trabajos de investigación hidromorfológica(Ollero et al, 2001(Ollero et al, , 2002 Escuer, 2004;Acín et al, 2005;Vilela, 2011;Muñoz-Narciso, 2014;Muñoz-Narciso et al, 2014, 2018Llena et al, 2016Llena et al, , 2018Llena et al, , 2019Llena et al, , 2020Béjar et al, 2018). Estos estudios han puesto de relieve el importante dinamismo de su cauce, el volumen de los procesos geomorfológicos registrados y los impactos de las infraestructuras hidráulicas, especialmente aguas abajo de embalses y derivaciones.…”

Reflexión sobre dinámica morfosedimentaria. Implicaciones para la gestión fluvial en un contexto de cambio global

“…Erskine (1997) informó que tanto los impactos físicos como los ecológicos tienen una firma a corto y largo plazo. Los primeros son aquellos relacionados directamente con la actividad minera directa: por ejemplo, la creación de nubes de turbidez o barreras de agua para la migración de peces (Béjar et al, 2018). Los principales efectos morfológicos son la incisión en el cauce (Marston et al, 2003;Rovira et al, 2005), con importantes consecuencias sobre la estabilidad de puentes y otras infraestructuras, la inestabilidad de los cauces (Wyzga et al, 2009) y el acorazamiento del lecho (Erskine & Green, 2000).…”