Sediment mining in alluvial channels: physical effects and management perspectives

Abstract

High intensity rains bring about landslides and high surface run -off in the upper catchment of the Balason River. Huge quantities of weathered materials as sediment load are being deposited in the river's lower course. The extent and intensity of this bed material extraction have taken such a toll that immediate attention is necessary to reduce the associated effects on the forms and processes of the Balason River's lower course. In this paper, an attempt has been made to closely analyse the prevailing effects of human interference noticed by the authors during this study. The methodology adopted during this study is field based. The changing cross sections and fluvial characteristic of the river were continuously observed. The extraction of bed materials was done directly from the riverbed and from adjacent flood plains and also from terraces. The extractions are responsible for the prevailing bed erosion and channel diversions because extraction pits are what are left behind. In the long term, if not controlled, the effects would be detrimental to the entire fluvial characteristics of the river.

Variabilidad espacial de los cambios de cauce en una rambla mediterránea en las seis últimas décadas (1946-2006)

“…These values range in the same order of magnitude as those observed in ephemeral streams in the USA (Rinaldi et al, 2005;Cadol et al, 2011) and Israel (Rozin and Schick, 1996). The time sequence is in most cases similar: incision is detected in the 1940s and increases later, especially in those rivers where gravel mining progresses (Rinaldi et al, 2005).…”

“…Causal interpretation has often been addressed through retrospective analyses of anthropogenic actions such as dam construction, reforestation, torrent control works, or river channelization (Bravard et al, 1997;Rinaldi, 2003;Surian and Rinaldi, 2003;Surian and Cisotto, 2007;García-Ruíz and Lana-Renault, 2011). Gravel extraction has also had a profound impact on rivers around the world (Kondolf et al, 2002;Liébault and Piégay, 2002;Surian and Rinaldi, 2003;Piégay et al, 2004;Rinaldi et al, 2005;Wishart et al, 2008;Surian et al, 2009).…”

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).…”

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

“…In both cases, a progressive reduction of sediment delivery at a regional scale, due to dam constructions, steep upland stream regulation, and land use change, has affected many regions, with the effects particularly evident in the piedmont areas of mountain regions Piégay, 2001, 2002;Surian and Rinaldi, 2003]. Recent (last century) intensive sediment mining has had one of the most important impacts, inducing further channel changes, with severe bed incision (maximum of 12 to 14 m) especially significant [Peiry, 1987;Bravard, 1991;Landon et al, 1998;Rinaldi and Simon, 1998;Surian and Rinaldi, 2003;Rinaldi et al, 2005]. Such morphological changes have had abiotic and biotic consequences followed by ecological and economical impacts [Bravard et al, 1999].…”