Television is full of lots of desperate situations. Show after show features mankind teetering on the edge of destruction. The most popular of these is The Walking Dead. For anyone off grid or living under a rock, The Walking Dead is an end of mankind style series where a few human survivors must outwit hordes of hungry blood thirsty zombies from devouring them. Another drawback of getting devoured by zombies in the show, is you become a zombie and then mindlessly kill other humans and your friends as part of the zombie army. The plot is not deep but some of the survival lessons are.
In one of the early episodes, the Zombies finally found the survivors in their mountain hideout. Even though they move less than one mile an hour and climbing hills is difficult without properly functioning limbs, they snuck up on them. One thing that instantly stood out to me was this convoluted idea of a passive fixed defense. Staying in one spot is seldom a good thing. It limits your options and allows your adversaries a clear point of attack. If you choose this strategy I would highly advise the use of patrols.
The use of recon soldiers, scouts, and quiet patrols will save your life. As enemies approach, meeting them in places they do not expect can save your compound. It can also disrupt their strategy and eliminate their advantage of surprise. If the Walking Dead humans had been doing this, they could have staved off one of the scariest attacks in the series. As far as how to structure patrols, I would make sure they remain unseen. The idea of the beat cop style guard out in the open is useless when an ambush or guerilla style attack is imminent.
Clandestine But Not Exposed
A good patrol is heavily camouflaged, quiet, and patrolling the areas around your compound. Very much like a sniper in wait, it is very likely they will come across an enemy who has no idea they are out there. This could be a huge tactical advantage against aggressors (or zombies) since you now dictate the terms of engagement and not them. I would also make sure to have a sniper in a high position overlooking the area the patrols are in.
Containment Boxes With Access Points
I would also make sure to structure your defense to funnel attackers into narrow choke points that limit their options. These can be disguised and structured with the use of thick brush, rocks, and logs which are less likely to be surmounted. Zombies do not climb well and human attackers will want to sneak up on you from low, seemingly hidden positions. The areas between the disguised brush and obstacles are your containment boxes. You can have hidden fox holes or points of access that your recon has already put in place allowing you the fastest access between the containment boxes.
Now look out for those zombies