Was Istanbul Hit by Floods or Urbanization?

Record rainfall in Istanbul, reaching 242 kilograms per square meter, has once again brought to the agenda the impacts of climate change and the city's preparedness for extreme weather events. Asst. Prof. Ahmet Adiller stated that not only meteorological conditions but also concrete urbanization, loss of green areas, construction in riverbeds, and infrastructure inadequacies are effective in severe rainfall turning into a disaster. “Flooding is a natural phenomenon, but the form of urbanization plays a significant role in its transformation into a disaster,” said Asst. Prof. Adiller, also drawing attention to the fact that excessive rainfall could contaminate drinking water sources.

Severe rainfall, which began on October 14 in Istanbul and caused floods and deluges in many parts of the city, has once again brought to the agenda the relationship between climate change and urbanization. According to data from the Istanbul Metropolitan Municipality (IMM), 242 kilograms of precipitation fell per square meter in Beykoz, marking one of the highest rainfall values recorded in the city in recent years.

Asst. Prof. Ahmet Adiller, Head of Environmental Health Program at Üsküdar University, evaluated the causes of the record rainfall in Istanbul, the role of concrete urbanization in flood disasters, the adequacy of the existing infrastructure, and the effects of floods on environmental and public health.

“Climate change paves the way for severe rainfall”

Stating that increasing global temperatures boost the atmosphere's moisture-carrying capacity, Asst. Prof. Ahmet Adiller said that this can lead to much more severe rainfall under suitable meteorological conditions.

Emphasizing that the rainfall experienced in Istanbul cannot be evaluated independently of climate change, Asst. Prof. Adiller said, “As average global air temperatures rise, the atmosphere's moisture-carrying capacity increases, which in turn paves the way for more severe rainfall under suitable conditions. The weather events we experienced yesterday and are still ongoing are extreme weather events that occurred due to suitable meteorological conditions on the ground prepared by climate change.”

Highlighting that the amount of rainfall in Istanbul reached extraordinary levels, Asst. Prof. Adiller continued:

“According to data from the General Directorate of Meteorology, based on data collected for Istanbul between 1950-2025, the average rainfall in October was recorded as 66 kilograms per square meter. In the rainfall that started on October 14, according to the data in the statement made by the IMM, 242 kilograms of rainfall fell per square meter in Beykoz. Although the rainfall experienced in Istanbul is extremely severe, it is not an unprecedented event for Turkey.”

“Much more severe rainfall was observed in the Mediterranean geography”

Reminding that excessive rainfall is not unique to Istanbul and similar events have occurred in the Mediterranean Basin in previous years, Asst. Prof. Adiller stated, “In 2018, 490.8 kilograms/mm of rainfall was recorded in 24 hours in the Kemer district of Antalya. Similarly, during Storm Daniel, which affected the Mediterranean Basin in September 2023, approximately 760 kilograms of rainfall was measured in Greece in one day.”

Asst. Prof. Adiller also reminded that Storm Daniel caused a major disaster in Libya, stating that these events in the region are important in showing the extent that extreme rainfall can reach.

“Flooding is a natural phenomenon, but urbanization plays a significant role in its transformation into a disaster”

Stating that the floods and deluges in Istanbul cannot be explained solely by the amount of rainfall, Asst. Prof. Ahmet Adiller pointed out that incorrect urbanization policies increase the impact of disasters.

Asst. Prof. Ahmet Adiller said, “Flooding is a natural phenomenon, but the form of urbanization plays a significant role in its transformation into a disaster. Concrete urbanization, the decrease of green areas, and construction in riverbeds make it difficult for rainwater to seep into the soil and drain naturally.”
Stating that infrastructure and urbanization conditions are decisive in causing serious losses in cities due to heavy rainfall, Asst. Prof. Adiller said, “In the disaster caused by Storm Daniel in Libya in 2023, in addition to heavy rainfall, the collapse of two dams exacerbated the scale of the disaster. Therefore, the magnitude of disasters is determined not only by the amount of rainfall but also by how prepared cities are for this rainfall. The problem Istanbul faces should be evaluated not only as a meteorological one but also as a problem of urban planning and environmental management.”

“Istanbul's infrastructure is not ready for extreme rainfall in all regions”

Evaluating the adequacy of Istanbul's current infrastructure against extreme rainfall, Asst. Prof. Adiller said, “It is not possible to say that Istanbul's existing infrastructure is capable of coping with extreme rainfall in all regions. Drainage systems designed according to past rainfall records need to be re-evaluated taking into account changing climate conditions.”

Emphasizing that identifying risky areas is crucial to reduce flood risk, Asst. Prof. Adiller pointed out the importance of protecting riverbeds and improving inadequate stormwater lines.

“It's not enough to just remove rainwater from the city”

Stating that nature-based solutions are important in making cities resilient to extreme rainfall, Asst. Prof. Adiller said, “In addition, permeable surfaces, green roofs, rain gardens, and rainwater harvesting systems should be widespread. The primary goal should not only be to remove rainwater from the city but to retain, store, and manage it in a controlled manner where it falls as much as possible. Because extreme weather events experienced with climate change can bring not only severe rainfall but also severe droughts.”

“Experiencing drought on one hand and floods on the other is not a contradiction”

Asst. Prof. Adiller stated that the experience of drought and water scarcity in Istanbul on one hand, and record rainfall on the other, can be explained by the effects of climate change, saying, “Although drought and floods seem contradictory, they can occur in the same region. Climate change affects not only the amount of rainfall but also its temporal distribution and intensity, i.e., the precipitation regime. According to the General Directorate of Meteorology data, Turkey's rainfall in 2025 was 27.6 percent below the long-term average. Despite this, short-term extreme rainfall can occur.”

“Record rainfall is not always an advantage for water resources”

Asst. Prof. Adiller stated that extreme rainfall can increase the amount of water in dams, but this may not always yield positive results for water resources, saying, “Severe rainfall can feed dams, but the rainfall needs to fall into the dam basins and be able to be stored. A significant portion of the rainfall that falls in a short period can be carried away by surface runoff, also carrying pollutants with it.”

Emphasizing that focusing solely on the amount of rainfall in water management is not enough, Asst. Prof. Adiller said, “Therefore, the main issue in water management is not just how much rainfall falls, but how long it falls for, and how much of this water can be safely stored.”

“Istanbul may face greater climate risks in the future”

Referring to the effects of climate change on the Mediterranean Basin, Asst. Prof. Adiller said, “Scientific predictions indicate that the risk of drought may increase in many regions of the Mediterranean Basin, while extreme rainfall may intensify, especially in the northern parts of the basin.”

Stating that Storm Daniel in 2023 is one of the important examples demonstrating the effects of climate change, Asst. Prof. Adiller warned, “For Istanbul and many cities in our country, the risks of heatwaves, drought, and extreme rainfall must be evaluated together in the future. We must plan our cities not according to past meteorological conditions, but by taking into account future climate risks.”

“Floodwaters can contaminate drinking water sources”

Stating that flood disasters not only cause loss of life and property but also pose significant risks to environmental and public health, Asst. Prof. Adiller said, “Floodwaters can carry wastes, microorganisms, chemical substances, and other pollutants from the areas they pass through. This can lead to the contamination of water resources and especially increase the risk of waterborne infections.”

Emphasizing that the safety of drinking water should be checked especially after floods, Asst. Prof. Adiller said, “After a flood, the safety of the drinking water network should be checked, water quality analyses should be performed, and warnings from authorized institutions should be followed. Water suspected of contamination should not be used, food that has come into contact with floodwaters should not be consumed, and submerged areas should be cleaned appropriately.”

“Boiling water does not eliminate chemical pollutants”

Asst. Prof. Adiller also made an important warning regarding the safe consumption of water after a flood, saying, “While boiling water can reduce the risk of infection by inactivating pathogenic microorganisms, it should be remembered that it does not remove chemical pollutants from the water.”
Stating that environmental and public health efforts should also be a fundamental part of disaster management after flood disasters, Asst. Prof. Adiller said, “Protecting environmental and public health during flood disasters is as important as evacuating floodwaters. Therefore, disaster management must also include water quality, waste management, and public health efforts.”

“We must act by accepting the existence of climate change”

Reminding that Turkey is preparing to host the United Nations Climate Change Conference (COP31) in Antalya between November 9-20, 2026, Asst. Prof. Adiller emphasized that efforts to combat and adapt to climate change should not be delayed.

Asst. Prof. Adiller called, “As we prepare to host the 31st Conference of the Parties (COP31) to the United Nations Framework Convention on Climate Change, we must act by accepting the existence of climate change, which is not accepted by some circles, and to delay this process as much as we can and adapt to changing climate conditions.”