We say it a lot, but it bears repeating: projects do change, and so do requirements. Managing the requirements effectively demands that you plan for change—specifically, you need to plan how you'll manage
the inevitable changes. Having a plan in place before the changes occur will spare you a great deal of risk, confusion, and wasted time.
If the changes happen early, before any requirements have been published or handed off, you'll probably be able to manage the changes smoothly within the requirements discipline. Naturally, you'll use requirements-traceability tools to confirm that all of the impacts are well understood.
When requirements change after they're published to the business stakeholders, developers, and other stakeholders, you'll need to manage the changes project-wide, not just within the requirements discipline. This is where it can get tough quickly, if you don't have an efficient requirements change management plan. As the business analyst, you're tasked with ensuring that everyone understands and follows a formal change control process, so the impacts of the changes are clearly understood by all.