Multi-purpose adaptation to SLR in Mediterranean urban coastal environments: the Barcelona case

The coast around Barcelona can be considered a good paradigm of the highly pressured Mediterranean coastal zone. The combination of decreasing river sediment discharges, increasing urbanization and infrastructure development makes this a very sensitive coastline. If we also consider potential effects of SLR, future conditions will significantly worsen and, for urban coastal environments, this will be a significant challenge since natural and anthropic conditions will largely constrain the development and implementation of adaptation measures.

The coastal zone around Barcelona comprises different typologies which are common along the Mediterranean: (i) city front formed by artificial beaches; (ii) longshore transport (Sl) dominated coastline with different barriers and without accommodation space due to intensive urbanization and existing infrastructures (coastal railway); (iii) Sl-dominated coastline with accommodation space; (iv) harbor. This variability determines that current processes and hazards largely vary along the coast, and that expected SLR-induced impacts will also significantly vary. This variability is also found from the socio-economic standpoint, with different stakeholders with different interests and needs. Some examples are: the Barcelona municipality requiring healthy beaches to provide recreation space for beach users, and protection against storm impacts. The railway operator that needs to maintain overtopping rates below a given threshold to maintain train operability. Campsite owners requiring a stable coastline to have enough recreation space for clients (beach users) and to avoid infrastructure damages. In overall, the combination of hazards and stakeholders provides a wide range of (Mediterranean) conditions to be found in urban and periurban coastal environments and, in consequence, it is a good test site to develop general adaptation strategies for this kind of coasts.

Previous works have identified suitable adaptation measures: (i) a sediment management strategy to maintain beaches within a given status; (ii) a new spatial planning to promote the adaptation of uses in areas with existing accommodation space; (iii) accept to “sacrifice” some beaches in highly eroding zones; (iv) structures redevelopment to maintain targeted functionality. In order to develop an efficient and integrated adaptation strategy for the entire coast, it is necessary to build up an adaptation pathway incorporating different measures and their corresponding tipping points (ATP). The goal is to assess adaptation needs with time (to answer stakeholders’ needs), to determine ATPs, and to properly define adaptation measures. For this purpose, it is necessary to have detailed information on expected conditions (forcing, processes and hazards) taking place during the adaptation period. Within this context, this work will present a suitable adaptation pathway to this coastal stretch to SLR to maintain functions currently provided by the coast and considering stakeholders preferences and needs. Presented solutions could be used as an example for other Med urban coastal environments.   

This work was carried out within the framework of the M-CostAdapt (CTM2017-83655-C2-1-R) research project, funded by the Spanish Ministry of Economy and Competitiveness (MINECO/AEI/FEDER, UE).