This chapter analyses how climate change may alter the level of potential impact on different infrastructures in the city of certain meteorological phenomena which, according to future climate projections, could vary significantly.
The dangers considered and which may have a significant impact on infrastructure include the following:
• Urban flooding
• Rising sea levels
• Storm surges
• River flooding
• Forest fires
The most extreme, most impactful or most unfavourable future scenarios have been selected from the available information (the full study can be found here) (in Catalan):
• Passive scenario (or also RCP8.5) represents the situation in which the targets set in Paris for greenhouse gases (GHG) would not be met and global temperature would be well above 2°C. This scenario has been applied to river flooding and forest fires. The A2 scenario of the Special Report on Emissions Scenarios (SRES), although an earlier projection than the Representative Concentration Pathways (RCP), is assimilated to the passive scenario and is applied to urban flooding.
• Pessimistic scenario, scenario is considered a much more extreme scenario, although with a very low probability of occurrence, but which some studies based on semi-empirical models (Rahmstorf 2007) support with sea level rises of up to 2 m due to the instability of Greenland and Antarctic ice sheets. Applies to maritime impacts (rising sea levels and storm surges).
This has been carried out by analysing the possibility that climate change-related dangers may or may not affect the different infrastructure and what the probability is, and whether the vulnerability of these infrastructure systems is considered high (service collapse) or medium (interrupted service).
It should be noted that in the methodology used, the assessment is qualitative and that the results obtained constitute an initial approximation that draws attention to certain points or infrastructure, without taking into account whether they have specific protection elements.
Thus, all the infrastructure has been assigned a level of danger and vulnerability in relation to the different impacts of climate change; the risk is, therefore, the product of danger and vulnerability.
The results of this calculation are shown in different maps, which are explained in the sections corresponding to each impact. The risk assessment maps identify all infrastructure classified according to the risk level: high or medium.
In order to easily visualise the variation of risk caused by the possible influence of climate change, in addition to the risk maps for the current situation and the climate change scenarios, comparative risk maps have been made. These maps show the areas in which the infrastructure may be in a situation of greater or lesser risk compared to the current situation.
In the current context, there is no guarantee that the planned or scheduled infrastructure will be developed, nor is it known within what time-frame it will be developed. Therefore, the possible impact of climate change scenarios has been based on existing infrastructure. Infrastructure and elements within the territorial scope of the city of Barcelona have been included, but also others which, if affected, although outside the municipal boundary, could have repercussions on Barcelona's infrastructure and services.
All the infrastructure included in this chapter are listed below, separated by themes and systems:
- ENERGY: high-voltage electricity network (high-voltage lines, generation plants and substations), high-pressure gas network (distribution network, regulation and metering stations (ERM), gas pipelines and regasification plants), oil pipelines and gas stations, and centralised climate control network (district heating and cooling (DHC)).
- WATER CYCLE: structural and unique elements of the regenerated, phreatic, sewage, rainwater and drinking water networks (drinking water treatment plants, desalination plants, Ter-Llobregat Water Supply Agency reservoirs, waste water treatment plants, injection and extraction wells, coastal and river interceptor collectors, pumping stations, stormwater detention tanks, rainwater lamination basins and combined sewer overflows (CSO))
- WASTE: waste treatment plants, technical cleaning equipment and pneumatic collection systems.
- TRANSPORT: main road network in Barcelona and the metropolitan area (motorways and dual carriageways, main roads and basic local network), rail network, overground stations and metro station exits.
- STRATEGIC ELEMENTS: strategic infrastructure (port, airport, Mercabarna and Barcelona's beaches).
- SENSITIVE FACILITIES: social services, health and education facilities.
- OTHERS (TELECOMMUNICATIONS AND SERVICES): network of service galleries and telecommunications towers.
The analysis of the risk of urban flooding affecting infrastructure is based on the identification of the areas of the city of Barcelona with the greatest risk of flooding, as detected in the Urban Flooding chapter. Based on a study of the functioning of the current sewerage network and its capacity to evacuate the flow of water associated with rainfall over a return period of ten years, the risk of flooding is determined according to the capacity of the network itself, the slope of the land and the surface area of the catchment area to which it contributes. The scope of analysis for urban flooding is only the municipality of Barcelona, as no detailed and uniform information was available for a wider area.
The map shows the results of the risk assessment for the current situation. From these results, the following can be highlighted according to the type of infrastructure:
The map shows the results of the urban flood risk assessment in the passive scenario for 2040. From this map, the following nuances can be highlighted according to the type of infrastructure:
Contrasting the results obtained for the level of risk for the passive scenario with those currently presented by the infrastructure with respect to the urban flood risk, we obtain the areas of the city where the risk of flooding varies. Marked in red are the elements or systems with an increase in risk in the city in the passive scenario for 2040. From the results, it can be seen that despite being widely distributed throughout the city, the areas where the increase in risk is most marked are Poblenou, Sant Andreu, Badal and Sant Antoni.
In the coming years, a series of modifications may occur in climate-related phenomena related to the sea with global effects from climate change. For this reason, maritime impacts on the city's infrastructure have been considered in terms of rising sea levels and storm surges separately.
For these phenomena, the most extreme scenario, the pessimistic scenario for 2100, has been considered. The pessimistic scenario predictions are much more extreme than the passive scenario projections for the end of the century, but due to the fact that there are new concerns about the stability of the Greenland and West Antarctic ice sheets that indicate that extreme sea level rise (up to 2 m) is physically possible, it has been considered appropriate to take this into account even though it has a very low probability of occurrence.
For the analysis of the risk of infrastructure being affected by a rise in sea level, we start from the maritime flooding , chapter, and work on the average level (permanent global rise in sea level considering the possible effects of climate change) and potential level (specific rise that takes place 2 or 3 days a year, also considering the rise from astronomical and meteorological tides). On the basis of these levels and the topo-bathymetry, the territorial extent of the corresponding maritime flooding is calculated, and in these areas an assessment is made of which infrastructure in areas with a direct connection to the sea may be affected.
The map below shows the results of the risk analysis of infrastructure in the face of rising sea levels in the pessimistic scenario for 2100. The main results of the risk analysis, applying the methodology described above, mean that the majority of possible risks are situated within the high risk category, with the following being highlighted by type of infrastructure:
The analysis of the risk of infrastructure being affected by storm surges is also based on maritime flooding, but in this case the current situation and the pessimistic scenario for 2100 are considered. The risk classification has been made considering that floods from storms with a return period of 10 years (T10) have a high level of risk, and floods from storms with a return period of 100 years (T100) have a medium level of risk. In accordance with the flood levels and the topographical bathymetry, the territorial extent of the corresponding maritime floods has been calculated, and an assessment has been carried out in the different areas of which infrastructure could be affected.
In a different way to that of sea level rise, it has been considered that areas which, despite being at a lower level than that which can potentially be reached, are located behind dykes or protective elements which shelter them from storms, will not be affected by storm surges.
It should be noted that this study was completed at the beginning of 2018. Subsequently, between 20 and 23 January 2019, the Gloria squall generated an exceptional storm surge in Barcelona where waves of 5 and 6 metres were recorded with maximum peaks that very probably exceeded 9 or 10 metres. The previous record for a significant wave in the city since records began in 1958 was that of 26 December 2008, with waves of 4.8 metres, a record that has now been broken by a wide margin.
As a result of Storm Gloria, there was an average loss of surface area of 30% on the city's nine beaches as a whole (of particular note was Bogatell beach with a 50% loss of surface area; Llevant 44%; Nova Icària 43% and Somorrostro 31%). But the worst damage was caused by the breakage of protective infrastructure (protective walls, diapasons, submerged dykes and breakwaters) along the entire seafront, which caused significant damage, especially in the Olympic Port and the Port of the Forum.
In this study, the protective infrastructure have not been modelled in terms of impact resistance and therefore the possibility of their breakage has not been considered. Therefore, as mentioned above, as long as the water does not exceed the level of the protection elements, the rear infrastructure are considered to be sheltered from the storm and this is the reason why the following maps do not consider many of the infrastructure that were damaged by Storm Gloria to be at risk.
The following maps show the result of the analysis of the impact on infrastructure in the event of storm surges:
Discussed below are the main results of the analysis applying the methodology described above. The main data to be highlighted from the current risk assessment map of the infrastructure are the following by theme:
The map below shows the results of the risk to infrastructure of storm surges in the pessimistic scenario for 2100. The results of the risk analysis by type of infrastructure are as follows:
The map shows the results of the comparative analysis of the risks generated by the effects of climate change on storm surges in the pessimistic scenario for 2100 compared to the current risks. In this case the situation deteriorates especially in the beach areas, the Forum and Sant Adrià, while the protection provided by the port breakwaters means that no changes are observed throughout this area.
Many global climate models indicate an increase in meteorological variability and a polarisation of the climate, effects which could be particularly marked in our Mediterranean environment. According to the Catalan Water Agency, it is very likely that the frequency of extreme downpours will double in the Mediterranean area, with maximum flows up to 20% higher than at present for return periods of T10 to T100 years.
The analysis has been carried out considering a return period of T100 in the current situation and in the passive climate change scenario for 2100. The analysis considers the impact that could result from the increase in the water level generated by flooding (related to the draught), the impacts caused by dragging (related to the speed of water flow circulation), and finally, the various impacts together, always considering the highest risk for each of the elements or sections of the infrastructure under study.
When presenting the results, because for future projections only a simulation of the final stretch of the Llobregat River at the end of the century is available for the passive scenario, the comparative map and the conclusions focus on this area of the final stretch of the Llobregat, although the entire area has been analysed for the current situation.
The map shows the results of the risk assessment for the current situation. From these results, which correspond to the entire study area, the following can be highlighted by theme:
The map shows the results of the risk assessment in the passive scenario for 2100. From these results, which correspond only to the area of the final stretch of the Llobregat river, the main data to be highlighted by theme are:
The most significant increase in risk is concentrated on the eastern flank of the Llobregat river, where the areas of Zona Franca-port, Bellvitge, Can Pi and Almeda are affected at different levels, unlike at present, where they are practically unaffected by the risk of river flooding. The western flank of the river Llobregat is less significantly affected, as a considerable part of the areas at risk of flooding correspond to the agricultural park, where the concentration of vulnerable infrastructure is less intense than on the eastern flank.
For the analysis of the risk to infrastructure of climate change, we start from the chapter on forest fires, in which the static danger of forest fires is calculated according to the danger of ignition (anthropogenic elements, flammability models, solar radiation) and the danger derived from the behaviour of the forest mass (fuel models, slope, orientation, altitude, firebreaks). To estimate the passive scenario in the year 2100, the areas where climate change will cause greater climate related stress and possible substitution of species due to climatic suitability have been analysed, thus modifying the fire hazard at the end of the century.
In the case of fires, an area of influence (buffer) of 500 m has been considered to assess the possible effects on service, as it is assumed that this is roughly the distance that might be affected by an evacuation or interruption of service as a precautionary measure. The Special Emergency Plan for Forest Fires in Catalonia (INFOCAT) assumes that the choice of an area of influence of 500 m is an important simplification, but that, in any case, it is a distance with guarantees for the type of fuels in Catalonia.
Discussed below are the main results of the analysis applying the methodology described above according to the type of infrastructure:
The risk to infrastructure in the passive scenario for 2100 remains almost constant compared to the current situation. There is a slight improvement in overhead power lines, structural and local roads, but some networks see their risk level get slightly worse, such as the gas network, secondary roads or surface rail, but these are almost imperceptible variations.
In this chapter, a methodology has been developed that enables an initial assessment to be carried out of the risk of a direct impact on infrastructure and services resulting from the natural risks that climate change may bring in the future. In this sense, it is difficult to summarise the risks that may arise, but those that stand out from the rest are mentioned below.
The sewerage system is one infrastructure that could be most affected, whether by river flooding, urban flooding or rising sea levels, and climate change could significantly aggravate this
Road and rail networks are among other infrastructure that are quite exposed to all impacts, especially fires, river and urban flooding. In the first two cases, moreover, structuring and strategic infrastructure for access to the city could be affected.
It should be noted that forest fires have the greatest impact on energy infrastructure. If we look at electricity infrastructure, except for those located in the Collserola Park, those at greatest risk are located outside, and in some cases far away, with little impact on Barcelona. The variations with climate change are less numerous and, theoretically, have a slight tendency to get worse, but a methodological review of this risk should be carried out.
One of the strategic elements that could be strongly affected by river flooding with climate change could be Mercabarna, with most of its roads potentially flooded. Also relevant is the possible effect on the airport from the rise in sea level, although, as has been mentioned, this is a pessimistic and unlikely scenario; and in any case, given the shallow depth, protection measures could be easy to apply. Beaches are the element most obviously affected by sea level rise and storm surges, which in the pessimistic scenario would be very significant
This analysis constitutes a first step towards assessing the resilience of urban infrastructure in Barcelona and its surroundings, which provides an initial approximation of the direct impacts on infrastructure, but more detailed studies should be carried out to complement this approximation and analyse the possible indirect impacts and cascading effects, which is why the interdependence matrices should be assessed and the time factor should be included in the analysis.