In Semarang urban coastal areas experience daily flooding from the sea during high tide (tidal flooding). Flourishing residential areas have changed into unhealthy slums with the nuisance of daily flooding in parts of the city. To overcome these problems a polder system was implemented to address the tidal flooding. The Semarang polder system is the first fully operational polder system in a densely populated urban area in Indonesia. This article describes the polder system that prevents flooding in the Eastern part of the city; the Banger polder area. An important element of the polder system is an emergency response plan that prepares for a flood emergency condition. The emergency response plan provides different emergency scenarios and identifies emergency levels and criteria. The management of emergency situations can be divided into four phases, namely mitigation, preparedness, response and recovery. The research results provide a detailed description of four emergency scenarios with 3 emergency levels for each scenario in the Banger polder area. The scenarios are; pumping stations operational damage, high-intensity rainfall in combination with high tide, failure of levees and dams, and an inflow of water from the west and east side of Polder system area.