The Sweet 16 of BSA Safety describe the measures we should use at all Scouting activities. The fourth point of the Sweet 16 is a Safe Area or Course (see below).
I think this is just something we need to keep in our heads when we are out with our Scouts. Of course, if an area looks unsafe, we wouldn’t let them go there. But we also need to actively look for hazards, like the dead branch that might fall on a tent or the area of the creek that looks OK at first glance but actually has a very deep spot.
4. SAFE AREA OR COURSE
A key part of the supervisor’s responsibility is to know the area or course for the activity and to determine that it is well-suited and free of hazards.