This is a very good idea for areas prone to Tornados, where the threat usually passes within 24 hours.
However, for areas prone to wildfires, flooding, mudslides and hurricanes, these storm shelters would be
a false sense of security, ie, how many days could it take for Rescue Crews to reach people with food and water?
Many times the roads are just not passible after these events, and it can take many days to clear them.
If the electricity went out, a generator would last only so long, (unless you kept solar PV panels inside
this shelter and/or a wind power set up).
Further, as we know, there's no such thing as a completely flood-proof, wildfire-proof, or wind proof design -
every structure has its limits, and these natural disaster events are getting more frequent and more severe.
For wildfires, flooding, mudslides and hurricanes, the best option would be to evacuate the whole area and
get far, far away.
But I really applaud the advance thinking you and others are doing to keep people safer.
Sincerely,
Carolyn Hunter, Architect
Context Architecture, Inc.
Durango, Colorado