Is my structure best for survival?

I am planning to have a mass migration in 1 of my stories and I thought of a few structures for different areas. Each layer around is different people. I have no idea what would be best for crossing a lake or a deep river. But others, I think I have a pretty good idea of what is best. So here they are:


This is my proposed structure for an open area, basically circles within circles. The pink layer is children and moms with babies. The next layer is pregnant women. After that is most people including any women on their period. Adolescents are old enough to be in this layer. Then there are 2 layers of defenders, a primary one the furthest out and the secondary one closest to the majority of people.

If a female defender is on her period at some point, she will go into the middle layer and a person from that layer will take her place. If someone becomes pregnant, that person will go into the second furthest layer in and if it is a defender, another person will take her place. Children when they are adolescents go from the layer furthest in to the middle layer. If 1 of the defenders dies, another person will take its place. For a primary defender having died, a secondary defender will become a primary defender and a person from the middle layer will fill the gap in the secondary defenders.


Going into a forest


Getting out of a forest


In middle of forest.

Are these structures best in terms of number of survivors in the areas I proposed them for? If not what kind of structure would be best? And what kind of structure would be best for crossing a deep and wide body of water?

 

Well I have thought of threats they would come across and how different predators would attack. If they are crossing a wide river in an area that is hotter for longer in the year, there are likely to be predators that hunt in a similar way to that of crocodiles, by surprise and doing a death roll to both kill their prey and rip it in chunks. These predators could swim underneath all the people if the water is deep enough and grab someone who is either on their period, pregnant, or young. This I think would be the biggest predatory threat overall.

As for forest predators, some hunt in packs like wolves. Others hunt alone like most big cats. Some jump from trees while others run when they get close. And others still, like bears will attack when they feel threatened but don't really hunt people.

Another threat really anywhere is encountering a creature that is venomous or poisonous. The people in the mass migrations have a built in defense against poison and venom but some creatures inject too much venom or too strong of a venom for that defense to be of any use. Similar thing is true for poison absorption. These have an about equal chance of injecting venom or poisoning any 1 person in the group but children are more likely to be severely affected by it.

And like you said currents are a threat as well, especially in narrower rivers which tend to have faster water flow.