A multidisciplinary geological research of the sedimentary processes (erosion, transport, deposition) affecting the sandy materials that characterized the lower Urdaibal estuary has been carried out. Three different methodologies have been implemented: a) the study of long boreholes in order to identify and locate in time the sedimentary accumulation phases and their forcing factors since the origin of the estuary up to the present; b) the study of modern sedimentary dynamics and hydrodynamics by means of estuarine surface samples, bed forms mapping, topographies and bathymetries, erosion/sedimentation rates determination, and the study of oceanographic variables; and c) the continuation of the geological monitoring of the sand dune regeneration process in the Laida beach initiated in 2001. Different geological disciplines have been used in order to determine the nature of the Holocene sedimentary record in this estuary, to characterize the different physical parameters affecting the sandy materials in the sub-, inter- and supratidal zones of the estuary, to carry out a cartography of affected areas by any of these sedimentary processes, and to quantify the sand volume involved in any of them.