To "move a boundary stone" refers to moving the landmark that marked the border of some property, which was a crime under Israelite law. (See: [[rc://en/ta/man/jit/figs-simile]])
Yahweh's wrath against Judah will be like a large stream of water that destroys them. In the scriptures, emotions and moral qualities are often spoken of as if they were liquids. (See: [[rc://en/ta/man/jit/figs-metaphor]])