The April 2019 flood in Shiraz was one of the most devastating natural disasters in the city's history, resulting in 22 fatalities, over 100 injuries, and extensive financial losses. This incident, as a social issue, highlighted weaknesses in urban management, encroachment on riverbanks, and lack of coordination among public institutions. This study examines the civil liability of public institutions in the occurrence and exacerbation of flood damages. The research method is descriptive and analytical. The findings indicate that Shiraz Municipality, through altering floodways, unauthorized constructions, failure to dredge waterways, and negligence in preventive measures, played a role in this disaster. Additionally, the Fars Regional Water Company, the Crisis Management Headquarters, and other institutions contributed to the severity of damages due to lack of oversight, ineffective coordination, and failure to fulfill legal duties. The analysis of causal relationships between the actions of responsible entities and the incident reveals that the disaster resulted from the collective contribution of multiple institutions in the form of concurrent (parallel) causes, and liability should be allocated based on the degree of fault of each entity.