A town situated in a hilly or mountainous region is preferable to one on open plains in the event of a worst case. Why? If and when roadblocks are needed to turn back the tide of refugees and looters, then towns on plains simply have too many vehicular ingress routes. By comparison, hill or canyon towns are typically limited by terrain to having just a few ingress routes. If the situation dictates that each ingress road must have defensible roadblocks, each manned 24 hours a day 7 days a week by three to 10 armed men, then the manpower requirements will jump considerably in towns with level terrain. Count the access roads and do the math!