The land where I built the base just vanishes and turns into river flows after the update...

Essentially its a living, evolving world.  Devs had stated to expect slight changes to the yard at every update

feelsbadman...

it's not really an evolving world, the game was maybe 20% done when "released".  They updated the map for new features to be put into place, this means map changes like this and the footprints can destroy your builds.  If you get up high enough, you see a ton of "just grass" area about the size of the "not just grass" backyard - about 1/2 the map is 'not just grass'. This tells me, combined with the 'under construction tape' that there is another 'map' yet to be added.

This game, is not "early access" like others, it is more "Polished Late Alpha Early Access" - so the alpha stage is really showing here.

For those that don't know what 'alpha' actually means, it is a stage in production where many core elements, features and functions are added, removed, or completely changed to better suit the game, story, or balance.  For another example - changing our inventory to allow equipped armor to not be in our backpacks - would be another 'core mechanic change' and if implemented right now, would be an alpha change.  A 'tool belt' that allows even part of our hotbar to be 'out of backpack' would be another core game mechanic change. Changing the map to allow fish/more diversity/story elements is another core mechanic change.

Your base just happened to be in one of these locations.  I fully expect the need to restart completely when the game is officially 'live' and out of Early Access.

agreed,  all the other games I've tested have made you restart from the beginning when they were "released to retail" as was called back then, not sure if that's the current term now since that one generation liked to change everything 😛 

Some gave you bonus items for the retail release for helping in alpha and/or beta testing.  I'm hoping they might do something like that here, not expecting, just hoping