According to the United Nations International Strategy for Disaster Reduction (UNISDR), floods are environmental disasters that affect the highest number of people and property. Along the Mediterranean coast and especially in Spain, history has seen frequent flood episodes. The number of publications referring to Spain’s flood risk has increased in recent years, and many news features detail the catastrophic effects of flooding in various regions.
Different types of flooding
A flood is the build-up of water, typically over dry land. It is caused by overflowing rivers or tidal waters or by excessive water from heavy rainfall. The four major types of flooding are coastal, urban, river, and flash flooding (recently, Spain has experiences countless flash flooding events).
Coastal flooding occurs when winds from a coastal storm or hurricane push an enormous wall of water from the ocean onto land; this is called a storm surge, and it can generate widespread devastation. There are also more harmless instances of coastal flooding called ‘sunny day’ floods. These occur when the sea washes up and spills into city streets or bubbles up from storm drains.
Urban flooding occurs when flooding from rainfall overwhelms the local stormwater drainage system of a densely populated area. This flooding can manifest in wet basements or sewer backups. In impoverished or socioeconomically isolated communities, even a small amount of rainfall can seriously strain community infrastructures.
River flooding occurs when a river, stream or dam overflows and submerges dry land. These floods can result from torrential rainfall or rapidly melting snow.
A flash flood is a sudden flood in a small catchment area (usually less than 1000 km2), occurring within 6 hours or less of the causative event (for example, heavy rainfall, dam break or rapid snowmelt) and often within 2 hours of the start of high-intensity rain.
The global significance of flooding
In 2020, the annual Report of the Weather Climate & Catastrophe Insight revealed that floods are the second most economically devastating natural threat globally, following closely after tropical cyclones.
An international study containing 34 research groups around Europe found that contemporary floods now cause over €100 billion worth of damage annually. Furthermore, the study showed that the general trend of flooding is increasing. According to Romero-Díaz, the last three decades of flooding in Europe are most important in terms of frequency and magnitude.
A further study conducted by the World Resources Institute (WRI) estimated that the global number of flood-affected people will double by 2030. That is, 147 million people will be affected by floods compared to the 72 million that were affected a decade ago. Economically, damage to cities and regions is expected to rise from $174 billion to an enormous $712 billion every year.
Analysing past flooding activity is crucial in evaluating future events and establishing sustainable management of the impacts. It will be difficult to adapt and protect coastal populations from flooding on the Spanish Mediterranean coast without sufficient planning.
The cost of flooding in Spain
In Spain, more than 200,000 people will be affected by coastal flooding triggered by climate change. Scientists expect this figure to rise to 340,000 by the year 2100. The Mediterranean region is particularly vulnerable to these catastrophic events because of its intense rainfall periods and torrential basins (such as the Segura Basin).
Recent floods in Spain
Flood events are more severe and damaging along the Spanish coastline. Flood risk is highest near Málaga.
Scientists are increasingly worried about the frequent torrential rains that engulf entire towns along Spain’s Mediterranean coast. Climate experts commonly cite global warming and climate change as catalysing factors for the increasing intensity and frequency of floods. While floods are ‘natural’ disasters, human factors such as urbanization and deforestation can greatly increase the economic, social and environmental toll of flooding.
2nd September 2021: Flash floods hit Catalonia
According to Catalonia’s regional weather service, over 215 litres of water per square metre fell in the region between 12 am and 6 pm. Following torrential rain, flooding swept cars and outdoor seats down the streets of seaside town Alcanar. The weather service also reported that the storm produced over 9,000 lightning strikes across Spain. Although there were no immediate reports of any fatalities, local authorities noted the severe damage to homes and businesses. One resident said her family ‘watched helplessly’ as ‘part of the terrace went into the sea.’ Authorities immediately began work to reopen roads and train lines blocked by thick mud and knee-high water.
Spain’s national weather service linked the increase in heavy rainfall to the climate crisis. The weather service spokesperson Rubén del Campo said:
‘Spain is observing, above all in points of the Mediterranean, periods of torrential rain that are more intense and longer periods of drought that are interrupted by these intense rains.’
29th August 2021: Flash floods in the Valencia region
Record levels of rain battered the Province of Castellón in Valencia (150 litres per square metre in just 24 hours). The torrential rain caused flash floods and severe damage to homes and roads. Citizens made over 160 calls to emergency services, and firefighters rescued three people trapped inside their cars on flooded roads. This torrent was the second incident of flash flooding in this area within a few days. Climatologists concerned with climate change predictions warned these events will become increasingly frequent in the future.
14th June 2021: Damaging flash floods in La Rioja
SOS Rioja reported over 50 weather-related incidents in 3 hours on the 14th of June, primarily in areas between Haro and Logroño. Emergency services rescued one person from floodwaters in Navarrete and another driver trapped in their car. The torrential rain created floods that blocked entire roads in Briones and Uruñuela. According to Meteo Galicia, 16 mm of rain fell in 10 minutes. However, most of the damage to streets and buildings was due to strong wind gusts of 76 km/h. Fuenmayor was the worst affected; two rivers that run through the town overflowed, causing serious damage to buildings and roads and flooding some houses.
5th March 2021: Flash floods in the Andalusia and Murcia regions of southern Spain
Severe flooding in southern Spain caused chaos as some streets morphed into raging rivers, carrying cars towards to coastline.
Over 24 hours in Andalusia, more than 127 mm of rain fell in Estepona in Málaga Province, and 77.8 mm in Tarifa in the province of Cádiz. Andalusia emergency services rescued 55 people from flooded homes in the Los Barrios where the Palmones River overflowed. Three of those people required medical attention for hypothermia. Authorities closed at least six roads in Algeciras, Tarifa and San Roque due to flooding.
Torrential rain and flooding also affected parts of the adjacent Murcia Region. Emergency services responded to 56 incidents related to the flooding, mostly in the municipalities of Águilas. Raging floodwaters swept away one person in their vehicle whom firefighters later rescued.
8th January 2021: Flash floods in Andalusia
Again, in the South of Spain, flash flooding brought by Storm Filomena battered streets. Estepona in the Malaga province recorded over 208 mm of rain in just one day, and Andalusian emergency services responded to 603 calls. The storm damaged at least 50 homes in Las Lagunas de Mijas due to flooding of the Fuengirola river. Sadly, two people died after being swept away in their vehicle by raging flood currents in Mijas. Firefighters were able to save five people from another car. In Algeciras, two people suffered injuries when a house wall collapsed under the pressure of heavy rain.
11th August 2020: Flash floods in Andalusia
In Córdoba, floods engulfed roads and homes in the towns of Palma del Río, Castro del Río, Bélmez and Puente Genil. Similarly, in Seville, pooling water blocked numerous roads and a driver had to be rescued from a stranded vehicle. In Herrera, located in the province of Seville, damage from the storm interfered with the power supply.
1st April 2020: Floods in Castellón in the Valencia region
Agencia Estatal de Meteorología (AEMET) reported that some areas in the coastal province of Castellón logged the highest daily rainfall totals in more than 30 years. Firefighters aided over 90 people trapped in vehicles or in their homes, and there were over 40 rescue procedures in Almassora, Boriana and Oropesa del Mar.
20th January 2020: Flooding in south-eastern Spain and south-western France
Storm Gloria triggered torrential rainfall and prompted evacuations in parts of south-eastern Spain and south-western France. Sadly, from the 20th of January, thirteen people died due to the coastal flooding, powerful winds and cold temperatures: four in Catalonia, two in Andalusia, five in Valencia, one in Castille and one in the northern region of Asturias.
The coastal town of Tossa de Mar in the Girona Province was flooded by seafoam. Flash flooding wreaked havoc in Cártama after the Guadalhorce River overflowed on the 24th of January. The floods left around 30 residents trapped inside their homes.
The Spanish government hosted an emergency meeting to discuss managing the impact of a storm. These impacts included damage to homes, public buildings and schools, damaged roads, collapsed bridges and railway lines and beach erosion.
Storm Gloria also caused torrential rain in parts of south-western France. There was 40 to 70 mm of rainfall in just three hours in some areas. On the 23rd of January (a notably intense day for rain), Meteo France said:
‘The equivalent of 4 to 5 months of rain fell in 72 hours in Roussillon…These heavy rains caused exceptional floods in the departments of Aude and Pyrénées-Orientales.’
Emergency services evacuated around 1,500 people from France’s south-western towns.
The relationship between climate change and rising flood trends
Long-term global climate change creates more extreme weather patterns and increases the frequency of floods. Moreover, land clearing processes and deforestation can increase flood risk as soil fertility and water-holding capacity declines.
The Director of the United Nations Environment Programme’s (UNEP) Global Resource Information Database in Geneva says:
‘While it is difficult to make a direct link between an individual extreme event [a flood] and climate change, it is clear that we need to be prepared to face more intense and more frequent extreme hydro-meteorological events due to climate change.’
Mounting global temperatures bring higher rainfall
As global temperatures increase, the atmosphere becomes warmer and dumps more water. When it rains, it is more likely to pour excessive amounts in a relatively short period of time. In regions where seasonal snowmelt aggravates flooding, hotter temperatures can create warmer rain that rapidly melts ice and snow, thus increasing the risk of flood.
More frequent storms and hurricanes bring higher rainfall
Climate change is increasing the frequency and intensity of extreme storms. Stronger storms and hurricanes produce greater rainfall, thus increasing the risk of flooding.
In America, 2017’s Hurricane Harvey inundated around 200,000 Houston homes and businesses with water and devastating floods. Scientists estimate that climate change made the hurricane’s rainfall three times more likely and 15 times more intense.
Stronger storms can also produce more forceful winds capable of generating storm surges. These surges pose a much greater risk today than they did a century ago because sea levels are higher and closer to land.
Higher sea levels increase high-tide flooding
Since the water starts at a higher level, storm surges can reach a larger landmass area and be more detrimental. Additionally, higher sea levels mean it no longer takes a fierce storm to cause coastal flooding. Rather, in many locations that lack natural barriers, flooding can simply occur with high tides. High-tide flooding can cause road closures, overwhelmed storm drains (urban flooding) and compromised civil infrastructure.
Should we worry about flooding?
Floods are among the most dangerous natural hazards in the world. As they sweep in (often suddenly), engulfing everything in their path, it seems humans have limited power to control and prevent these natural beasts. European scientists are perplexed by how excessive damage caused by flooding occurs in some of the world’s wealthiest and most technologically proficient countries. Despite major investments in flood forecasting, preparation and management, it seems these swamps of water continue to strain many European communities.
According to a study published in Geophysical Research Letters, climate change could make intense, flood-inducing storms 14 times more common before the next century. While natural flood measurement strategies (such as diversion canals and coastal defences) may reduce the effects of flooding, these defences are unlikely to succeed in the face of rising global temperatures and sea levels.