Even in rural areas there will be movement of “refugees” At some point someone will have to tell them go away, keep moving, or some other communication. The person communicating will be exposed visually and through sound. Either a fortified position, armor or both will make this a safer duty to perform. Of course a natural formation of rocks or something might be found in the right place, but how many people will have that circumstance? Only a unknown percentage will acknowledge a sign that reads DANGER STAY OUT – your statement here (use your best judgment).
BTW if you were to place signs to warn people to stay out what should the sign say?