And you would be happy to just sit by and bide your time, watch your house flood, see all your belongings destroyed, and then pay a liar lawyer to take ten years of your life and your life's savings while you sue the developer?
If we're talking in theory and the couple's illegal filling of their property caused continual flooding of yours, you would have on ongoing problem. Each time there was enough rain you would suffer flooding and a have another cause of action. Awarding monetary damages each time isn't what a civil court would do.
One alternative to treat it like a taking of your land - forcing the couple who illegally filled in their land to buy yours because they've rendered it unfit for its purpose due to the repeated flooding. But that's not fair. You were there first and obeyed the rules. Why should they have the right to break the law and force you to either endure repeated flooding or move?
The other and appropriate alternative is to cause them to remedy the situation that's causing the repeated flooding. Remove the illegal fill. Restore their property to the point that it's not causing flooding on the property of another.
Because repeated civil suits is something the system will tolerate, and you shouldn't have to sue each time there's a flood. And allowing the party that caused the flooding situation to remedy it by buying out the flooding land isn't the just remedy.
Making them return their land to the condition it was in before they took their illegal acts, and before they caused repeated floods on adjoining land, is the appropriate remedy.