Access the full report
November 9, 2026
About the October 2026 Istanbul floods
From October 13 to 17, intense rainfall caused significant flooding across parts of Türkiye, particularly Istanbul. A low-pressure system over the eastern Mediterranean interacted with an upper-level trough extending from the Balkans, drawing moisture-laden northeasterly winds across the Black Sea. Atmospheric instability and persistent rain bands generated prolonged heavy rainfall, potentially enhanced by coastal convergence and local topography.
Rainfall observations recorded 274.4 mm at Beykoz in northern Istanbul over 48 hours between October 14 and 15, while modeled accumulations exceeded 250 mm in parts of northern Istanbul from October 14 to 17. Marsh Re analysis of maximum daily rainfall against historical European Climate Assessment & Dataset (ECA&D) precipitation data indicates 1-day rainfall return periods exceeding 100 years at several locations across the affected region, highlighting the exceptional local severity of the event.
Insurance market impacts
Human and economic loss
The flooding claimed nine lives across Istanbul and neighboring Kocaeli and caused significant damage to residential and commercial properties, industrial facilities, and vehicles, with particularly severe impacts in Sarıyer's Ayazağa district. Across Istanbul, Governor Davut Gül reported approximately 3,000 homes and businesses seriously damaged and estimated direct and indirect economic losses of around 10 billion TRY (€180 million). By October 20, the Insurance Association of Türkiye (TSB) reported 3,017 flood-related claims notified to insurers, totaling approximately 4.5 billion TRY (€81 million) in reported claim amounts, comprising 2,041 property and industrial claims and 976 motor claims. These figures remain preliminary and do not represent settled or ultimate insured losses.
Urban flooding
The concentration of damage in heavily urbanized areas highlights the importance of local catchment characteristics, development along watercourses and drainage capacity in determining flood impacts. Rapid runoff in small urban catchments, alongside the modification of natural drainage channels, can exacerbate flooding, emphasizing the need to characterize both fluvial and pluvial hazards.
Türkiye's flood protection gap
Although earthquake is Türkiye's peak catastrophe risk, flood may contribute materially to losses at more frequent return periods. Unlike compulsory earthquake insurance under the Turkish Catastrophe Insurance Pool (DASK), flood coverage generally remains voluntary. The Insurance Association of Türkiye (TSB) estimates fire/property insurance penetration in Istanbul at approximately 17% to 20%, compared to 43% for comprehensive motor insurance, indicating a substantial protection gap.
Complexities in flood risk assessment
Quantifying flood risk through historical experience is challenging. Rapid inflation, exchange-rate movements, changes in rebuilding costs and insured exposure, and limited historical claims data complicate comparisons between events. These factors make it difficult to establish a consistent historical benchmark for flood losses or reliably assess their contribution to portfolio-level risk. These challenges highlight the need for a probabilistic approach that translates local flood hazard, exposure and vulnerability into portfolio-level loss estimates.