The city of Barranquilla in Colombia has one of the major stormwater management issues in the world. Due to the lack of a stormwater drainage system in more than 90% of its urban area, the runoff flows on the streets during rain events with dangerous flow rates of up to 100 m3/s for a 50-years return period. The permeable areas are little and the steep slopes of the city cause supercritical flow and flash floods on many streets with high velocities. This has negative consequences such loss of human life, damage to infrastructure, and economic losses. A 1D model was setup in PCSWMM to assess the flow rate, velocity and hazard levels on the streets for different rainfall events. This model was performed considering a process of characterization and calibration of the drainage conditions of the city, including land survey and field measuring by using rain gages and flow gauges installed in the monitoring system PLUVIAL.CO (www.pluvial.co). The hazard levels results were compared with the safety criteria for people (1.2 m2/s), obtaining up to 6 m2/s from recorded events in 2014 and 20 m2/s for events with 100-year storm. The hazard, velocity and depth maps are presented in the article.