The river just stops somewhere

Good morning everyone. I'm in the bus to work again.  This weekend was quite productive while in the end, I only got a little progress. The problem was that my game totally broke and I hadn't made the effort to back it up yet, which was stupid. On the other hand, there were things not working correctly which I were trying to fix and which I could not, so it's ok. I'm not beyond that point anyway.

I'm still working on the procedural level generation for Holocene and I'm using a Zenva Academy course to guide it. I'm not just following it, but have it guide my progress and do the refactoring that it's screaming about while I'm writing the code. Instead of linking noise generation scripts without attributes to every single object, I'm using static ones for that kind of purpose, because a larger level might turn a slow and laggy level if I'm not careful.

Right now, I have a grid of tiles which in turn are grids of vertices and blocks. Any vertex had a height and that stands for the height of a given place in the world. It also had a heat and moisture value which make for a biome value together. Right now, any biome can have one kind of tree. I'm going to change that later. There's no reason why tropical rainforest can only have one kind of tree. 

Last thing I added was rivers. While I was following the course, I kind of knew this was not going to work correctly:

The river gets a random origin point somewhere above a certain height threshold. On the right on there picture. Then, for every step of the way, it finds its lowest neighbouring vertex and goes there until it reaches the sea. Here is the problem. The way to the sea is hardly ever a simple downhill path. There are bumps on the way.  It the real world, rivers overcome those bumps over time, but here they don't. This makes that the river will just stop in a valley, zig zag around a bit and look weird like in the picture.

Seeing this thing is easy, but I have not yet come up with a solution. It seems like there needs to be more planning, although that feels counterintuitive. The origin is fine, I think and the first downhill part is too, but then we need to make sure to keep some longevity. We need to make sure the river does not stop in a valley (or it should form a lake) and we need to make sure the river flies not surround itself.

I'm thinking of a system that had the rivet have a general direction to go, to a shore somewhere. I'm not sure how to make sure it does not have to be a straight line, but I'll manage. The other thing I'll probably do is have the river have a force to be able to lower vertices around it. When the river has gone down, it should be able to dash through small uphill sections by lowering that section.

I'm thinking about this some more. Hopefully, I'll have a good solution soon.