The main objectives of the actions implemented in the upper estuary of the Oka River are: (i) Improve the resilience of the estuarine ecosystems to the impacts of climate change, such as sea level rise and changes in the water regime; (ii) Increase local biodiversity thanks to the recovery of part of the ecosystem's functionality; (iii) Increase the sustainable public use of the natural space of the Urdaibai Biosphere reserve.

Restoration activities aiming to recover the previously existing marshland have been implemented in the upper estuary of the Oka River, including the permanent flooding of the Barrutibaso area part of the upper estuary. Moreover, the functionality of part of the original intertidal channel of the Oka River’s lower section has been recovered. As part of these restoration activities, some of the dykes and other artificial barriers have been removed to improve the estuary renaturalisation, while embankments have been constructed to create lagoons that will become intertidal zones in the future. The restoration of marshlands formerly drained for sanitary reasons can help the estuary to face climate change. Marshes, in addition to protect against the effects of sea level rise, play an important ecological role providing new habitats to various species of amphibians and birds and improving their adaptation capacity. Moreover, the permanent presence of brackish water favours the elimination of some invasive species (e.g. Baccharis halimifolia).

The restoration project also included other interventions and activities:

• The construction of a 14 km pathway network and of a pedestrian and cycling bridge connecting the neighbouring municipalities among each other and to the Oka river estuary, aiming to facilitate sustainable visit of the area;
• The development of tools for environmental education, the most notable being a smartphone application providing information on the habitats, species and culture of the area. Moreover, panels have been installed providing on-site information on local habitats and species.
• Eradication of invasive species (as Baccharis halimifolia and Cortaderia selloana) in an area of approximately 700 ha of the estuary.