The accurate estimation of the resources required to implement a change in software is a difficult task. A method for doing this should include the analysis of the impact of the change on the existing system. A number of techniques for analysing the impact of a change on the source code have been described in the literature. While these techniques provide a good example of how to apply ripple effect analysis to source code, a weakness in these approaches is that they can be difficult to apply in the risk assessment phase of a project. This is because the source code is often not very well understood at this phase, and change proposals are written at a much higher level of abstraction than the code. It is therefore often the case that in practice subjective impact analysis methods are used for risk assessment and project investment appraisal. The underestimated resources for dealing with the ripple effects of a change can result in project schedules becoming so tight that only the minimal quality is achieved. This paper surveys existing ripple analysis techniques and then presents a new technique for the early detection of ripple effects based on a simple graph‐theoretic model of documentation and the themes within the documentation. The objective is to investigate the basis of a technique for analysing and measuring the impact of a change on the entire system that includes not only the source code but the specification and design documentation of a system, and an early phase in the maintenance process.