Changes in fluvial sediment storage from aerial photograph analysis (river Narcea, Nothern Cantabrian Range)

Abstract

Work aims at providing estimates of volume changes in active sediment storage for lower River Narcea (NW Iberian Peninsula) during the last six decades, through surface changes, identified from aerial photographs taken at different dates. A five step procedure was followed: 1) Georreferencing of aerial photographs. 2) Mapping of active channel surface and fluvial bars, on each aerial photo. 3) Aerial photography correction regarding water flow stage and channel width. 4) Assumption of a thickness for active sediment layer. 5) Estimating sediment volume changes. Estimated changes have been linked to human interventions on the studied reach of channel (embankments and dam). A reduction in the volumes of active gravels is observed, mainly linked to the abandonment of formerly active deposits and its colonization by vegetation.