In early September 2024, an unseasonal rain swept over parts of the Sahara, leaving behind scattered blue lakes on land typically bone-dry and barren. Water settled upon dusty basins and ancient riverbeds, supplying some of the world’s most arid spots with more rainfall than they had been privy to in decades.
Errachidia, a desert city in southeastern Morocco, saw nearly 7.6cm (3in) of rainfall across just two days – about half its average annual total, and four times what it would typically receive in September. Tagounite, a rural commune 354km (220 miles) south of Errachidia, recorded an even more atypical 9.9cm (3.9in) of rain in just 24 hours.
Deluges of this magnitude are rare in Saharan Africa, but numerous experts anticipate that extreme weather occurrences in desert regions are liable to become more commonplace.
For the Sahara, a place synonymous with arid survival, the very presence of water may soon be its greatest existential threat.
During September’s unusual wet spell, the typically dry Lake Iriqui – nestled in the shadow of the Anti-Atlas mountains – was briefly restored to its former glory. Isolated by a dam built in the 1970s to regulate the Draa river, the lakebed suddenly sprang back to life, offering locals a rare glimpse into the region’s past.
But the rains also left devastation and death in their wake. Resultant flood waters claimed the lives of at least 18 people across Morocco, including 10 from the southern villages of Igmir and Aoukerda, located 1,000m (3,281ft) up in the Anti-Atlas mountains.
Both communities were overtaken by sudden and unprecedented torrents of muddy water, with the floods arriving so swiftly that residents had no warning, and no chance to prepare.
How desert floods happen
Such floods occur due to a complex mix of atmospheric, oceanic and ecological factors. As global temperatures rise, sea waters are warming, causing increased evaporation. This boosts the humidity in the atmosphere, creating the conditions necessary for intense, cyclone-like storms.
In the Mediterranean, these are called ‘medicanes’, and they are now impacting parts of North Africa’s arid coastlines, as well as those on the Arabian Peninsula.
However, desert floods aren’t tied solely to climate change. They are also influenced – and can be exacerbated – by natural oscillation patterns such as the Atlantic Multi-decadal Oscillation (AMO) and the Atlantic Zonal Mode (AZM).
These see long-term variations in sea surface temperatures, which alternate between warmer and cooler phases.
The AMO cycle, for example, goes through these phases every 60 to 80 years, and when in its warm phase, can increase the likelihood of extreme weather, such as increased rainfall. The AZM, meanwhile, is the Atlantic equivalent of El Niño – the complex climate mechanism that causes warmer temperatures in the Pacific.
The interaction between these natural cycles and long-term climate change trends can complicate flood forecasting and management in deserts, where even brief shifts in rainfall can lead to serious impacts.
“Many desert regions are used to experiencing only very irregular rainfall. All deserts are different, but they often have few plants, poor soils and hidden river channels. This means when heavy rain hits, water can rapidly run off and pool on lower-lying land,” says Prof Hannah Louise Cloke OBE, hydrology expert at the University of Reading.
Desert soils are particularly vulnerable to flash flooding due to their composition and structure. In moderate rainfall, sandy or loamy desert soils absorb water well. However, when intense rain strikes, raindrops compact the soil surface, transforming it into a barrier to water infiltration.
In urban areas or deserts near towns, degraded soils and accumulated sediment add another layer of complexity, leading to poor absorption and increased sediment runoff.
What’s more, due to these regions being unaccustomed to heavy rainfall, local emergency services often lack the capacity to handle the sweeping challenges posed by such flooding.
Also, local infrastructure is not designed to withstand such conditions, and in certain cases human-made structures have even amplified the effects of severe weather events, transforming challenging situations into unmanageable ones.
A prime example of this occurred in Derna, Libya, in September 2023, when the city experienced catastrophic flooding after Storm Daniel hit the region.
As the storm raged, two dams – the Derna Dam and the Abu Mansour Dam – on the outskirts of Derna collapsed, sending an estimated 30 million cubic metres (1,100 million cubic feet) of water rushing into the city. That’s roughly equivalent to about 12,000 Olympic-sized swimming pools worth of water.
The flood swept away vehicles and homes and killed an estimated 11,300 people – close to one-ninth of the city’s total population.
“The existence of these dams meant people were able to reside in otherwise dangerous regions, like on a floodplain,” explains Moshe Armon, senior lecturer at the Hebrew University of Jerusalem’s Institute of Earth Sciences.
“The dams were designed to protect the city's population from floods, but eventually acted in the opposite direction. The specific impact of these dams caused, we believe, an almost 20 times increase in damage.”
In the aftermath of the tragedy, the recovery efforts were hampered in part by ongoing political unrest in Libya, and by what many Derna residents considered inadequate rescue efforts by authorities.
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Not if, but when
Given that these downpours have not been very common in the past, ignoring these infrastructural frailties wouldn’t typically have had catastrophic consequences.
But, as desert floods are projected to become more frequent, these vulnerabilities could be exposed with increasing regularity, putting communities and infrastructure at greater risk.
“It’s not a matter of if, but when we’ll see intense desert floods,” says Essam Heggy, a Research Scientist at the Microwave Systems, Sensors and Imaging Lab (MiXIL), at the Viterbi School of Engineering at the University of Southern California, in the US.
“The coastal areas of all North Africa, from Morocco to Algeria, Tunisia to Egypt, as well as the United Arab Emirates, Saudi Arabia, Oman and Qatar are at the highest risk.”
Deserts have long endured harsh droughts and sporadic rainfall, but the downpours that devastated Derna in 2023 – and those that revived long-dry lake beds in Morocco this year – are seen by many scientists as part of a troubling pattern that is being driven by both human-made and climatic factors.
“These recent floods are reminders that almost nowhere is immune from flood risk. Regional climates have shifted in previous centuries, but never before has there been such widespread and fast changes to climatic patterns.
"The pace and scale of the current changes are occurring everywhere, and too quickly for ecosystems to adapt without risking collapse,” says Cloke.
The Middle East and North Africa (MENA) include some of the areas most likely to be impacted by the effects of climate change.
A 2022 study by the Greenpeace Research Laboratories based at the University of Exeter found that the MENA region is warming almost twice as fast as the global average, while a report in the same year released by the International Monetary Fund (IMF) predicted that by the end of the current century, average temperatures in the Middle East and North Africa could be 5°C hotter than they are today.
“In general, Africa is expected to get hotter and drier, but some regions are already seeing, and are projected to see, more intense rainfall events. This is either from shifts in the tropical monsoon-influenced rainy seasons, or due to the impact of more intense, if less regular, tropical cyclones hitting the coast,” says Cloke.
Over the past decade, intensified desertification has left the MENA region increasingly vulnerable. As vegetation has disappeared and the land has hardened, its resilience to sudden torrents has diminished, fuelling a cycle that will leave the region ever more susceptible to extreme weather.
“Deserts are much more complex than most people realise. Any stress will lead to rapid breakdown in the ecosystem,” says Prof Paul Carling, Emeritus Professor in physical geography at the University of Southampton.
“These soils are fragile and readily disturbed. Climatic instability and human pressures on these areas, including poorly designed flood protection infrastructure, can rapidly lead to degradation.”
All this has led experts to emphasise the urgent need for greater resilience and preparedness in desert regions.
They say local governments and communities need to invest in infrastructure specifically designed to withstand extreme weather, and to develop comprehensive disaster management plans that take into account the increasing frequency – and potential devastation – of such events.
Worryingly, Heggy believes that the risk of flooding in these regions is still not being taken seriously enough, and he admits to becoming increasingly frustrated by the widespread downplaying of climate risks in the MENA region.
“We can’t resolve a problem for which we have insufficient climate observations. Today, most academic research programmes on climate extremes in the MENA area are being shut down. The perception is that these events are unlikely to occur and, therefore, not worth studying.
“About half of the surface of coastal cities in the MENA area, mostly the parts of the cities on the coastal side, need urgent transformation to be able to defend against the increase in storminess and coastal erosion, as well as sea level rise. However, this needs wider research and investigation.”
Carling has also been vocal about the critical need for increased data and information.
“The level of relevant scientific knowledge in these countries is often poor with respect to understanding the processes of flash flooding. Additionally, what knowledge there is does not seem to be taken up by local authorities.
“In the case of Egypt, for example, the government is promoting development along the southern Red Sea coast. The drainage here comes from desert mountains to the west via ephemeral streams that may flood only every 10 years or so.
"These roads often have no culverts (underground structures that redirect water) to allow flood waters to pass, or the culverts are completely inadequate. New building is taking place in areas of high flood risk, including in dry channels that will rapidly fill during rare floods.
“In my opinion, most disasters due to flooding in deserts are due to poor planning of where people should live, and the infrastructure design taking little or no account for floods,” he adds.
All of which begs an obvious question: what can be done?
Forecasting for the future
Prof Christopher Dickman of the University of Sydney’s Desert Ecology Research Group, in Australia, believes that one of the most effective approaches will be to use predictive mapping of where flash floods are most likely, so as to reliably forecast the timing of probable flooding events.
He also suggests that more drastic measures could be required.
“Policy solutions may include moving people from particularly risk-prone areas and preventing further settlement there,” he says. “Also, improving knowledge of flooding risks for local people via education outreach programmes and developing evacuation and rescue plans for when flash floods occur will be important,” Dickman adds.
Armon also believes that delivering more accurate projections and committing to real-time forecasting will be essential to helping vulnerable communities better prepare for these flooding events.
However, he is also determined to point out that, even if predictive calculations become more accurate and effective, nature will always retain an element of volatility that cannot be fully controlled or mitigated.
“Floods are not going to disappear, and there's nothing we can do about that. What we can do is be prepared, and perhaps try to mitigate such floods using distributed, nature-based solutions that are not relying on damming large parts of desert streams, simply because there's always going to be a flood larger than what we are prepared for,” Armon says.
In terms of infrastructure solutions, a greater use of canals, culverts, flood channels and stormwater retention basins could help to limit the impacts of flash floods when they occur. Additionally, restoring desert vegetation around rivers and basins could reduce erosion, improve water infiltration and help to slow runoff.
These solutions will only be effective, however, if local authorities acknowledge that they are vulnerable and commit to proactively addressing the challenge. As it stands, the MENA region finds itself at a crossroads, and the next steps will be crucial.
Building a resilient future will require investment in science and technology, along with a reevaluation of how and where communities construct their homes. As flooding events become more frequent, widespread community engagement will be essential to create environments that not only survive but also thrive amid climate change.
According to Cloke, “To reduce the risks, everyone needs to be ready to plan for the worst, and be more accepting of the fact that flooding can happen anywhere.”
About our experts
Prof Hannah Louise Cloke OBE is a hydrology expert at the University of Reading, England. Her work has been published in World Weather Attribution, United in Science and Natural Hazards and Earth System Sciences.
Moshe Armon is a senior lecturer at the Hebrew University of Jerusalem’s Institute of Earth Sciences. His work is published in Communications Earth & Environment, The Science of the Total Environment and Natural Hazards and Earth System Sciences.
Essam Heggy is a Research Scientist at the Microwave Systems, Sensors and Imaging Lab (MiXIL), at the Viterbi School of Engineering at the University of Southern California, in the US. He has been published in Nature Sustainability, Nature Communications and Earth's Future.
Prof Paul Carling is an Emeritus Professor in physical geography at the University of Southampton. His work has been published in Communications Earth & Environment, The Cryosphere and Progress in Earth and Planetary Science.
Prof Christopher Dickman is an Emeritus Professor in Life and Environmental Sciences at the University of Sydney in Australia. He has been published in Journal of Applied Ecology, Austral Ecology and Biological Conservation. He has also co-authored three books: Cats in Australia: Companion and Killer, Secret Lives of Carnivorous Marsupials and Review of Cat Ecology and Management Strategies in Australia.
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