I think we are gonna dry up and blow away.

[TheSilverBuick]

This again can cause floodings when a dike gives way because it has become too light to the water back.

It's not just a weight thing. Most dikes are built out of low-permeability clays. And clays generally swell and shrink as they absorb and release water, some substantially, pick your clay carefully! So when they dry out they shrink, and then crack, like mud cracks. Then when they get wet again have zones of weakness along the cracks as well as the cracks being conduits for water.

Typically the center of a good dike is made of good clay, then buried/covered by more conventional dirt that can deal with water addition and subtraction while insulating the inner clay layer from such fluxuations.