All decisions will have some element of risk associated with them and how the risk is to be ultimately managed can shape the actual decision itself.
Risk can be effectively managed ONLY if it is understood.
Understanding can only be realised with sufficient information available to provide appropriate context to the risk in relation to the decision to be made and the potential impact it will have on the business.
An Enterprise Architecture, whilst not pretending to be omniscient, can provide the necessary information to assess the risk and for the decision maker to garner enough understanding of both its impact and likelihood of occurring to formulate an appropriate decision and possible mitigation.
The information held within the Enterprise Architecture repository may not be complete when tasked to assist in supporting any given decision but will be better than not having any at all.
The outcomes of decisions, made as a consequence of the understanding reached about specific risks, should be fed back into the Enterprise Architecture improving future risk assessment.
With even better information new risks can be better understood with the business benefiting from better decisions and less unintended consequences.