PetaJakarta.org is a research project led by the SMART Infrastructure Facility, in collaboration with the Jakarta Emergency Management Agency (BPBD DKI Jakarta) and Twitter Inc. The Joint Pilot Study for the project was operationally active from December 2014 to March 2015, and PetaJakarta 2.0 launched in December 2015. During this time, the project enabled Jakarta’s citizens to report the locations of flood events using social media network Twitter, thereby contributing to a publicly-accessible real-time map of flood conditions at PetaJakarta.org. This data was used by BPBD DKI Jakarta to cross-validate formal reports of flooding from traditional data sources, supporting the creation of information for flood assessment response, and management in real-time. Through its integration with BPBD DKI Jakarta’s existing disaster risk management (DRM) information ecosystem, the PetaJakarta.org project has proven the value and utility of social media as a mega-city methodology for crowd-sourcing relevant situational information to aid in decision-making and response coordination during extreme weather events.