Escalating incidents in complex environments can lead to severe cascading effects and quickly become extremely difficult for emergency services to handle. Such incidents can have enormous consequences with respect to life, property and the environment and for both infrastructure and the general public. These consequences can in many situations have both direct and indirect effects, not only in the immediate surrounding geographical area but also across very large areas, potentially extending across borders.CascEff will improve our understanding of cascading effects in crisis situations through the identification of initiators, dependencies and key decision points. These will be developed in the methodological framework of an Incident Evolution Tool which will enable improved decision support, contributing to the reduction of collateral damages and other unfortunate consequences associated with large crises. Use of the Incident Evolution Tool will be demonstrated through its implementation into three different incident management and training platforms representing different end users in the project.The work proposed in this project will significantly improve the ability of Incident Commanders to manage complex incidents by improving our understanding of initiators, dependencies and key decision points through the use of the proposed Incident Evolution Tool. This will introduce additional information and decision support into the incident management process, beyond the knowledge available from experience alone by introducing a number of alternative options for response strategy. This tool will be run a priori for bespoke crisis originators identified during the project and will include multiple timelines as well as physics based representations of the environment and the impact of decisions on the mitigation of cascading effects.