The collective impact approach is a structured form of collaboration whereby organisations and individuals from different sectors all work together on a common agenda for solving a specific problem. The Adelaide Zero Project is a collective impact initiative seeking to end rough sleeping/homelessness in the Adelaide inner city.
Collective impact is based on the understanding that existing approaches to creating change are too often ineffective for solving complex issues. More information about collective impact can be found here.
Further reading: Stanford Social Innovation Review Collective Impact