What it means
を余儀なくされる means that someone is forced to do something or is left with no choice but to undergo an action because of circumstances, pressure, or an unavoidable decision. It attaches to an action-related noun, such as 避難 or 中止, followed by を. The construction emphasizes that the subject does not act voluntarily. It is formal and especially common in news reports, official statements, and academic or business writing.
Usage note
The subject should normally be a person, group, or organization that can be forced to act; an event or place is generally not a natural subject. The noun before を usually denotes an action or outcome, rather than an ordinary physical object.
How to use it
大雨が続けば、住民は避難を余儀なくされます。
If the heavy rain continues, the residents will be forced to evacuate.
大雨が続けば、住民は避難を余儀なくされる。
If the heavy rain continues, the residents will be forced to evacuate.