Istanbul Technical University (ITU) Climatology and Meteorological Engineering Department faculty member Prof. Dr. Mikdat Kadıoğlu said that what happened, especially in the northern districts of the city, created a situation that the region could not cope with with its own means.
Stating that the differences in the same city on the same day show that the characteristics of the place where it falls and the infrastructure in the city are decisive in the occurrence of the disaster, as well as the amount of rainfall, Kadıoğlu said, "According to the preliminary rainfall data of the last 24 hours as of October 14, at 23.03, 230.3 kilograms of rainfall fell per square meter in the Beykoz district of Istanbul. This amount corresponded to almost 3.5 times the city's average total rainfall of 66.3 kilograms in October." he said.
Drawing attention to the impact of heavy rainfall in the northern districts in a short time, Kadıoğlu emphasized that issuing a single yellow warning throughout the city would not be enough to explain the location and severity of the risk.
Pointing out that the amount of precipitation is measured by the height of the water falling per square meter, Kadıoğlu said, "1 millimeter of precipitation means 1 liter, that is, 1 kilogram of water falling per square meter. 100 kilograms of precipitation per square meter creates a layer of 10 centimeters in height if the water does not flow and leak. The precipitation measured in Beykoz means approximately 24 tons of water falling on a 100 square meter roof." gave the information.
RECORD RAINFALL IN ISTANBUL WAS CREATED BY THE COMBINATION OF 3 FACTORS
Talking about the factors behind the record rainfall, Kadıoğlu made the following evaluations:
"The combination of the water temperature of the Black Sea, which reached approximately 19.5-20 degrees, with the cold air coming from the Balkans and the north wind carrying moisture over the sea, was effective in the heavy rain in Istanbul. Warm seas can feed heavy rains by providing moisture to the atmosphere, but a special attribution study is required to link a single rainfall event directly to climate change. Climate change can increase the severity of extreme weather events. Even if there was no climate change, the building built on the stream bed would receive water, and the panel in the basement would still receive electricity. "The underpass would be filled again. Climate change magnifies the danger somewhat, and we magnify the disaster. El Nino cannot be shown as the direct cause of the rainfall in Istanbul."
Kadıoğlu pointed out that almost all of the precipitation on concrete and asphalt surfaces passes into surface flow without infiltrating the soil and flows by gravity to the lowest points, stream beds, underpasses and basements.
Kadıoğlu pointed out that excessive rainfall alone does not cause a disaster, but that wrong land use, construction in stream beds, inadequate infrastructure and delayed administrative decisions increase the damage, and said, "Rain is a danger. Disaster is the result that occurs when that danger meets our unprepared, wrongly located and mismanaged city. According to this definition, what happened in Istanbul is a disaster on a local scale. But let's not call it a 'natural disaster'. Rain is natural, disaster is man-made." he said.
"RAINWATER AND WASTEWATER LINES MUST BE SEPARATED FROM EACH OTHER"
Explaining that floods in Istanbul are shaped by meteorological conditions as well as the structure of the basin and human intervention, Kadıoğlu pointed out that the transformation of stream beds into roads, parking lots and residential areas increases the risk.
Pointing out that the combined operation of rainwater and wastewater systems in Istanbul also poses a problem, Kadıoğlu also warned that sewage can backfire in heavy rains and that water entering basements poses a health risk.
Kadıoğlu emphasized that infrastructure solutions are not limited to just laying larger pipes and said:
"The streams that were covered and turned into roads, parking lots and residential areas should be reopened, and the fillings that narrow the stream beds should be removed. Roof water should be stored, parks and squares should be designed to temporarily retain water during rainfall. Rainwater and wastewater lines should be separated from each other. Flood maps should be prepared and construction should not be allowed in risky areas without taking these maps into consideration. The problem is not only the insufficiency of pipes, but also the closure of the natural flow paths of water and cities not being planned accordingly."
Recommending that electrical panels and generators be placed above the flood level, limiting the use of basements in risky areas and establishing water barriers at car park entrances, Kadıoğlu noted that a "flood building regulation" based on flood hazard maps should be prepared.
Kadıoğlu, who wanted maps to be published where citizens can learn about the flood risk through their addresses, suggested installing barriers that automatically close when the water level reaches 15 centimeters in underpasses and early warning systems on stream banks.
