A hazard is something that presents a danger to your client. When people talk about being 'at risk' of an emergency or disaster, it means that a hazard exists and your client is vulnerable to it.
Your clients may not be able to avoid a hazard, but good preparation can make them less vulnerable to it.
Tip: buddy system
By facilitating meetings and get-togethers, a small community service organisation helped their clients to get to know their neighbours. They set up a buddy system so that clients knew who they could go to in an emergency.