Climate change adaptation scenarios for the Litoral de las Tres Chimeneas waterfront

In the current context of climate emergency, it is necessary to identify the strategies needed for the adaptation of urban habitats to the effects of climate change. This issue is even more urgent when it comes to the development of new spaces in the city, especially when these are located along the coast.

Since 1990, there has been a visible environmental recovery of public use of the northern coastline, from the Port of Barcelona to the municipality of Montgat. Its recovery began in 1982 thanks, among other things, to the construction of the Levante collector. This infrastructure has improved the quality of bathing waters along the entire coastline. Subsequently, the successive urban transformations, first those linked to the 1992 Olympic Games, and later those of the 2004 Forum of Cultures, along with the recovery of the coastal front in the area of the Besòs River mouth, have enhanced the improvement of beach conditions and increased their public use.

To all of them is added today the transformation of the coastline of the Three Chimneys. The development of a new residential neighborhood with amenities and a seaside promenade linked to the stabilization of the beaches is planned. For this purpose, various studies and works have been carried out, coordinated by the Besòs Consortium. The Consorcio del Besòs has been working since its establishment on improving biodiversity, conserving open spaces, enhancing public spaces, urban layouts, and facilities in the Besòs area.

The reflection and proposals presented below represent an essential exercise in anticipation that aims, on one hand, to propose alternatives and, on the other, to open the dialogue about the relationship between the city model and the effects of global warming in the area known as the Three Chimneys coastal front. An area of approximately 270 km², extending from the mouth of the Besòs River to the port of Badalona, with a coastline of 1.5 km, of which 985 m are in the municipality of Sant Adrià del Besòs and 552 m in Badalona.
It is essential to recognize that we are in an area of great vulnerability to the effects of climate change, which not only threatens the utility/effectiveness of public spaces and their associated infrastructures but also the integrity of the entire ecosystem typical of this coastline.

Approaching the design of this new coastal front while considering the effects of climate change involves identifying the processes that will be relevant in the medium and long term (2050 - 2100). This is what is recognized as slow variables, which include, among others, the gradual rise in sea level or the increase in temperature. These variables are in turn responsible for flooding, erosion, or loss of ecosystems, among others.
Climate change has consequences on the mean sea level and the meteorological tide. The two main issues to which the coastline is subjected are flooding (permanent due to the rise in mean sea level; potential considering the rise in mean sea level and the variations in astronomical and meteorological tides; extreme, which combines the previous effects and the effect of waves during extreme storms) and erosion (due to the fact that all the beaches in the area lack a sandy cordon or nourishment that would allow them to react to sea currents and the rise in sea level). In addition to these threats, the area also experiences impacts on biodiversity (marine, coastal/riverine, and terrestrial ecosystems), impacts on infrastructure, and impacts on the urban system.
Thus, the strategy is based on the design and implementation of new resilient landscapes that combine those elements that the coastal system had in its initial state, before its anthropization: wetlands, dunes, beaches, and the new Besòs-Badalona coastal park.

- Wetlands

In the area closest to the mouth of the Besòs, a series of topographies are generated between the beach profile and the riverside park located next to the Marina Besòs municipal sports center, creating a new habitat, the wetlands. A controllable system of flood basins with freshwater from rain and from the Besòs River, as well as with saltwater thanks to the action of the waves. In this way, the introduction of new species is achieved, promoting the overall biodiversity of the area and the renaturalization of the urban edge close to both the riverbank and the sea.

- Dunes

It is proposed to improve the resilience and stability of the emerged beach through a double dune cordon, as the dunes are sand reserves that mitigate the effects of storms and are the habitat of species of community interest. The dune most exposed to the beach area and therefore more prone to impacts from people or animals will protect the inner dune. This inner dune will be subject to management and maintenance. The outer dune will also be the most exposed to storms, so it can be constructed with a core of geotextile filled with sand. This double dune cordon is intended to serve as the element of connection with the sea when the emerged beach is flooded by the gradual rise in the mean sea level.

- Beaches

The beach is the most vulnerable area of this entire coastal front and is subjected to increasing erosion that will lead to its long-term disappearance. Therefore, stabilization measures are proposed (improvement of the equilibrium profile, adjustment of the beach profile with geotubes and fill) to achieve the desired surface width. More precise studies will indicate whether this coastline should be interrupted with perpendicular elements (geotubes, projections, or submerged artificial dikes) to improve its stability.

- Besòs Badalona Coastal Park

The proposal must address the dual nature of the area: local and metropolitan. For this reason, its heart, regardless of the future of the old thermal power plant, is the configuration of a large coastal park. A park accessible to the residents of nearby neighborhoods and to those coming from the rest of the metropolitan area through the Besòs river park and the seafront promenades of Badalona and Barcelona. And indeed, without a doubt, in the current context of continued global warming, the Besòs River is destined to be a climate refuge of metropolitan significance, a space for diversity and encounter.