Pumping stations are important flood mitigation infrastructure used in coastal cities to remove accumulating floodwater from low-lying areas, where drainage is naturally poor due to very low slope gradient. In coastal mega-cities situated in developing nations, these pumping stations are often vulnerable to trash blockage as a result of frequent dumping of solid waste in water bodies. Given that blocked pumps are common causes of drainage infrastructure failure, the inability to identify the most vulnerable pumping stations can lead to inefficient allocation of limited resources for preventative maintenance of the drainage system. This study proposes an approach for measuring and ranking the vulnerability of pumping stations to trash blockage. In this approach, a trash blockage vulnerability index (TBVI) is developed based on the concepts of exposure, sensitivity and resilience. Using a graph-based network analysis technique, the proposed TBVI is applied to assess and rank the vulnerability of pumping stations in one of the most representative coastal mega-cities − Jakarta, Indonesia. The results show that TBVI can point to the pumping stations that are most vulnerable to trash blockage. Such information are vital to decision makers when planning and prioritising infrastructure to be serviced or upgraded as part of flood preparedness in coastal cities.