Set thermostat to away when flood sensor triggers

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!