Unveiling the possible causes of July 2023 unprecedented flood in National Capital Territory of Delhi, India

Delhi, the capital city of India, faces disastrous floods due to a rise in the water level of the Yamuna River. The city experienced an unprecedented flood with water levels reaching 208.66 m on July 13, 2023. This flood was the worst in the flood history of the National Capital Territory (NCT) of Delhi, as several areas got submerged under more than 2.5 m of floodwater, which took several days to recede. This paper, therefore, aims to unveil the possible causes of the July 13, 2023 flood. The data were collected from various secondary sources such as research papers, technical reports, magazines, newspapers, websites, etc. The analysis revealed that heavy rainfall in the upstream region for 4 consecutive days (8–11 July) and subsequently a release of excess water (10,187 m3 s⁻1) from the Hathnikund barrage were the prime causes of this unprecedented flood, which was further compounded by a phenomenal rise in built-up area and a decrease in area under forest, agriculture, and water bodies. Besides, the reduced carrying capacity of the Yamuna River due to encroachment of its floodplain with agriculture and urban settlements, aggradation of the riverbed, and discharge of solid waste from industrial as well as urban drains played a significant role in intensifying this unprecedented flood. These identified factors can be a benchmark for urban planners in the future in mitigating the risks associated with floods in NCT Delhi.