A new IHCantabria study for the Port of Santander concludes that the Bay has reached a “dynamic equilibrium”.

The most current data certifies that erosion rates on the beaches of Somo and Loredo and the advance of El Puntal have been significantly reduced since the dredging and dumping management policy began to be designed on the basis of scientific knowledge.

The Mesa de la Bahía, the collaborative body between administrations for the comprehensive management of the estuary, met today to analyze the results of the ‘Hydrodynamic study of the navigation channel and the Somo-Loredo El Puntal beach system’. This report, commissioned by the Port Authority of Santander (APS) to the Foundation Institute of Environmental Hydraulics of Cantabria(IHCantabria), provides an updated perspective on the morphodynamic evolution of the estuary, revising previous forecasts that were based on data from more than 30 years ago.

The main conclusion of this new study is that the beach system and the navigation channel are currently in a situation of “dynamic equilibrium”. Key to this result has been the new APS-funded data collection campaign, which has included high-resolution topo-bathymetric surveys to accurately map the shape of the coast and seabed, detailed bottom characterization to identify the different habitats, and the use of sophisticated numerical models to quantify littoral processes.

This new knowledge base has made it possible to accurately quantify the current reality of the estuary. The data show that the erosion rates on the beaches of Somo and Loredo have been considerably reduced. In the period 1960-1990, retreats of 1.7 meters per year were recorded in Loredo and 1.5 m/year in Somo. In contrast, the new data reflect that, in the period 2016-2024, there was a reduction in that rate to 0.50 m/year and 0.20 m/year, respectively. In parallel, the research certifies that the progradation of Punta Rabiosa (the advance of the arrow of El Puntal), which historically advanced at a rate of more than 10 meters per year, has been reduced between 2016 and 2024 to a practically null rate (0.20 m/year).

This stabilization is the direct result of the dredging and discharge management policy implemented since the 1990s, which was based on scientific knowledge. The system is therefore reaching a stable morphodynamic equilibrium thanks to current management, but being a low-lying coastal area it is highly sensitive to new climatic challenges.

Currently, the mostsignificant challengefacing the Bay is sea level rise. This rise may cause the shoreline to recede and increase the frequency and intensity of flooding and wave overtopping events, increasing the vulnerability of infrastructure and dune ecosystems. Therefore, the current stability should be the basis for implementing proactive measures to adapt to climate change.

The study includes a set of proposed measures to maintain the current balance and ensure the long-term sustainability of the Bay. The main actions included in the report are:

• Recovery of flood zones: 224 hectares of tidal marshes in the Boo and Cubas estuaries are proposed for restoration. This measure, a clear example of a “nature-based solution”, involves reconnecting former tidal spaces to the estuary flow. The restoration has a double benefit: ecological, by recovering a marsh habitat vital for biodiversity (breeding and feeding area); and hydrodynamic. By increasing the floodable area, the tidal prism (the total volume of water that enters and leaves with the tide) increases. A larger tidal prism generates stronger tidal currents, which would improve the self-cleaning capacity of the inner channels, helping to slow their siltation.
• Dredging of the secondary channel: maintenance dredging is planned for the Pedreña channel. The objective is to recover its operability, which has been seriously impaired by the progressive accumulation of fine sediments. This silting, which the study quantifies as a loss of draft of up to 30% in recent years, compromises safe navigation, especially at low tide. The intervention would directly improve inland connectivity, ensuring the viability of key services such as passenger transport to Pedreña and Somo and access to nautical facilities.
• Strategic replenishment of the beach system: on the other hand, and in order to offset the effect of climate change, it is proposed to contribute 4 million cubic meters of sand from external deposits identified on the continental shelf, such as those located off the cliffs north of Santander or in the vicinity of Cape Ajo, whose viability and characteristics are compatible with native sand. The most favourable alternative would be to gradually provide this volume (150,000 m³ per year for 27 years), pouring it into the same submerged area as at present.

“Maintaining optimal navigability in the channel to ensure the maximum possible draft is vital for the access of ships to the docks and the proper functioning of port operations, but, at the same time, we are aware that our role in the future of the estuary is crucial,” explained the president of the Port Authority of Santander, César Díaz. “Therefore, we will continue to work in line with the recommendations of IHCantabria to maintain the current balance of the Bay in the long term and, before the end of the year, we will start an annual campaign, over the next five years, dredging the navigation channel from Punta Rabiosa to Somo to improve its operability, especially in the low tides alive.”

“For the first time in more than two decades, we have a complete and updated database that allows us to confirm that the system has reached a balance,” emphasized Raúl Medina, CEO of IHCantabria and co-author of the study.“However, this stability is the starting point, not the goal. This is where Plan Bahía becomes fundamental, as it is the backbone tool that ensures that decision-making is coordinated. The future of the estuary depends on all the administrations acting together, and this Plan is the framework that will allow us to define the next phase of actions in a consensual manner.”

The president of the Santander Port Authority reaffirmed his commitment to the sustainability of the estuary: “From the APS we will continue to do everything in our power to reconcile our responsibility as the driving force of industry in Cantabria with the generation of 14% of GDP and 11% of employment in the region, with the utmost respect for the conservation of the Bay”.

The next step of Plan Bahia

The Hydrodynamic Study commissioned by the Port of Santander is part of the progress made by the Mesa de la Bahía. This forum brings together all the administrations involved in the

The main objective of the project is to promote the development of the estuary’s management and the University of Cantabria. Its main objective is to promote the Integrated Coastal Zone Management in the estuary through Plan Bahía, the strategic project promoted by the Bureau to define a consensual management model.

The final objective of the Hydrodynamic Study presented today, the definition of a proposal for sustainable management of the navigation channels of the Port of Santander, is perfectly aligned with the objectives of Plan Bahía (abbreviation of Integrated Management Plan for the Bay of Santander). And the measures proposed in the document respond directly to three of the ten problemsidentified in the Diagnostic Phase of the Plan: the erosion of beaches and the lengthening of El Puntal, the loss of draft in the interior of the Bay and the recovery of maritime areas previously filled in the estuary.

The conclusions of the Hydrodynamic Study will now be integrated into the set of measures proposed in Plan Bahía, which will respond to the ten problemsidentified in the estuary, and whose final conclusions will be presented in the coming months.