I think “Dry Wetspot” and “Switch Changes mode” found in the market place could do this, with a virtual switch.
Create Virtual switch: FAQ: Creating a virtual Device
Create a new mode called “Flood” (or whatever)
Install smartApp “Switch Changes Mode”. Set it up for virtual switch to change mode to Flood
Have Nest-Manager automation set Away on mode “Flood”
Install SmartApp “Dry Wetspot” and set it up when detects moisture trigger virtual switch.
Good Luck!