Emergency response involves collaboration among search and rescue workers, medical staff, transportation coordinators, and others to save human lives and minimize damages. While carrying out local activities, members of the teams must also attend to new events happening elsewhere that may affect their work, and be prepared to adjust their activities accordingly. This paper describes a computer supported coordination system, DACE (Dependency-based Awareness and Coordination Environment), which offers a scalable solution to coordination in emergency response. The system serves as a cognitive aid to human actors in both maintaining a group mental model of the overall collaborative activities and their dependencies, and determining the effects of events as they propagate through the web of dependencies. We demonstrate the principles and utility of the DACE system through a hypothetical scenario of search and rescue exercise. This work contributes to the goal of scaling up awareness-based coordination in emergency response.