İstanbul's streams overflow during rainfall: How has urban development reshaped the city's waterways?

Istanbul faced its heaviest rainfall in 84 years on October 14 and 15, triggering severe flooding that claimed four lives and disrupted daily life across the city. Rainfall levels reached 272 kilograms per square meter in some areas, according to the Istanbul Metropolitan Municipality, marking one of the highest readings since 1985. Floodwaters submerged homes, businesses, and roads, trapping drivers in their vehicles and halting traffic in multiple districts. Rescue operations continued as authorities worked to evacuate stranded individuals and clear blocked pathways. The storm began on the night of October 14 and continued through October 15, with the heaviest downpours concentrated in the early hours. By October 15, the death toll had risen to four, including a 14-year-old boy electrocuted in a puddle in the Fatih district, a 34-year-old who suffered fatal injuries after slipping on a sidewalk in Sarıyer, and a construction worker who fell into a well while draining floodwater in Beykoz. Authorities confirmed seven people remained hospitalized, though specific details about their conditions were not disclosed. Istanbul Governor Davut Gül announced that schools would remain closed on October 16, extending the suspension of classes from the previous day. The decision came as officials anticipated continued rainfall for the next two to three days. Authorities urged residents to avoid streambeds and low-lying areas prone to flooding, warning that even light rain on October 16 could lead to further flooding due to already saturated ground. The impact of the rainfall was felt across the city, with more than 1,000 flooding incidents reported. Vehicles were partially or fully submerged in several locations, and rescue teams worked to extract people stranded in floodwaters. In Sarıyer, workers at a concrete plant were evacuated using a front-end loader after floodwaters cut off their escape routes. One of the rescued workers described being stranded for 14 hours before being pulled to safety. Floodwaters also affected infrastructure, with 46 aircraft unable to land at Istanbul’s airports due to adverse weather conditions. Along the Bosphorus, runoff from swollen streams turned sections of the coastal waters brown, with discoloration extending roughly 200 meters from the shoreline in some areas. A 2023 master plan by the İstanbul Water and Sewerage Administration (İSKİ) revealed that 64% of the city’s 168 major streams had undergone physical alterations. Landscape architect Dr. Hülya Dinç’s 2015 doctoral dissertation highlighted that dense urban development had significantly impacted these waterways, reducing their ability to handle heavy rainfall. Her research indicated that 80% of the 168 major streams were connected to developed areas, with only 33 remaining untouched by settlement. Dinç’s findings pointed to the narrowing of streamside protection zones over the years, beginning with the abolition of buffer requirements in 1988. This allowed for increased development along streambanks, exacerbating the risk of flooding. She emphasized that the loss of riparian ecosystems and the reduction of natural water flow contributed to the severity of the recent floods. As the situation unfolded, authorities continued to monitor the weather and coordinate relief efforts. Meteorologist Professor Dr. Mikdat Kadıoğlu warned that the saturated ground would make even minor rainfall potentially dangerous. With the storm expected to persist through October 17, the focus remained on ensuring the safety of residents and managing the aftermath of the unprecedented rainfall.