Dense, self-built settlements along riverbanks within Asian cities are often excluded from the planning realm, which ensures governments lack knowledge of how particular communities function. The magnitude of land area and population, dynamic local economies, organic policy making processes, and scarcity and consistency of data challenge research on flood impacts and possible solutions in Asian cities. Resultantly, a deeper understanding of alternative and more dynamic forms of environmental management is necessary. The focus of this paper is to analyze the usefulness and challenges of participatory mapping in relation to urban floods, particularly community mapping and crowd-sourced mapping. This analysis is based on the assumption of participatory mapping discourse that participatory mapping increases communities' negotiation power to improve their livelihood. This paper employs participant observation and ethnographic interviews within the Ciliwung River corridor in Jakarta. Specifically it focuses on activists and residents in river communities in relation to participatory community mapping exercises conducted since 2012 and a new crowd-sourced flood mapping system launched in December 2014. Participatory community mapping and crowd-sourced flood mapping, as two forms of community-based mapping approaches to floods, are viewed as potential tools to overcome urban flood hazards while raising disaster awareness among city residents. Community mapping is a method of visualizing a neighborhood's communal memories and embedded power relations, while a crowd-sourced flood map visualizes vulnerabilities and may become a tool for information sharing for the betterment of the spatially and socially fragmented city.