Rotate Texture Via Face Direction

Afternoon all.

I hope I can explain this properly. I imagine it is possible.

So, for a landscape material, a beach layer. I have a texture like this

And I want it to always align to the slope towards the waters edge. Doesn’t have to be super accurate.

That make sense? Any ideas how I could do something like that without multiple painted layers?

Cheers all. Any help is very much appreciated!