Response of a river sediment budget after historical gravel mining (the lower Tordera, NE Spain)

Abstract

The channel of the lower Tordera River (Catalan Coastal Ranges) was intensively mined between 1956 and 1987, at an extraction rate 14 times higher than the replenishment rates. Mining caused incision of up to 2 m over the whole reach, leading to damage of infrastructures and affecting the groundwater system. In this paper we analyse the response of the river sediment budget by means of sediment transport measurements (both in suspension and as bedload) and topographic surveys. Historical data on mining activities was used to verify current values of sediment transport and to locate the main extraction areas in the long profile of the river. This has led to an integrated methodology that can be useful for assessing and managing current and future sediment deficits in heavily mined rivers. In the lower Tordera, a minimum of 3 million cubic metres of sand and gravel were extracted, especially from two gravel pits still visible as concavities in the river's longitudinal profile. Nowadays, 15 yr after mining ceased, the river shows during dry periods a general tendency towards aggradation (3.6 mm yr À1 on average and up to 12 mm yr À1 in central sections where mining took place), but a slight long-term tendency to erode the riverbed. Sediment yield at the entrance of the study reach attains 552 000 t yr À1, while net sediment deposition reaches 16 400 t yr À1 (78% as bedload), mostly during small floods in dry periods. Estimated time for the river to recover pre-extraction bed-level is of the order of 420 yr.

Geomorphological Approaches for River Management and Restoration in Italian and French Rivers

“…These geomorphic changes observed at a regional scale in both France and Italy are also observed in the Pyrenees [i.e., Garcia-Ruiz et al, 1997;Rovira et al, 2005] and can be considered a general response to the pressures of human society across Europe, with remarkable differences to what is observed in other parts of the world where deforestation and its impact is more commonly described. The research undertaken in the Drôme catchment has demonstrated that the afforestation has generated a deficit of sediment that is propagating downstream [Liébault, 2005;Liébault et al, 2008].…”

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

“…Los principales efectos descritos en la literatura incluyen: la alteración de la geometría del canal, la disminución del nivel freático debido al sobredrenaje, el incremento del tamaño de partículas del lecho y el incremento de sedimento fino (p.ej., Kondolf, 1994). Se han realizado numerosos estudios de los efectos geomorfológicos de las extracciones de áridos (Rinaldi et al, 2005;Rovira et al, 2005), pero son escasos los trabajos que han analizado específicamente el efecto de estas actuaciones en el transporte de sedimentos finos en suspensión (arcilla, limo e incluso arena; Brown et al, 1998). Durante las operaciones de extracción aumenta el material en suspensión debido a la erosión lateral al extraer material del canal (Warner et al, 1977), al paso de maquinaria por el cauce del río (Forshage y Carter, 1973) y a la remoción de materiales y exposición de sedimentos finos al romper la coraza del lecho (Lagasse et al, 1980).…”

Rapid channel incision of the lower Pearl River (China) since the 1990s as a consequence of sediment depletion

“…For example, effects of sediment mining on alluvial river incision have been huge (Rinaldi et al, 2005). This has been well documented for the rivers in California (Harvey and Shumm, 1987;Collins and Dunne, 1990;Kondolf and Swanson, 1993;Kondolf, 1994;Kondolf, 1997;Sandecki and Avila, 1997), Washington (Collins and Dunne, 1989), Italy (Surian and Rinaldi, 2003;Rinaldi and Simon, 1998;Rinaldi, 2003), Spain (Rovira et al, 2005), France (Peiry, 1987;Petit et al, 1996;Bravard et al, 1999;Gaillot and Piégay, 1999;Arnaud-Fassetta, 2003), UK (Sear and Archer, 1998), New Zealand (Page and Heerdegen, 1985) and Australia (Davis et al, 2000).…”