The Floodways environment was added in Rundown 005 and resembles an overgrown sewers area with multiple vertical layers in most of the large rooms.

This environment is currently the only one that cannot appear alongside other environments in the same expedition.
The rooms in the Floodways are some of the largest of all environments in the game, featuring large bridges and many open areas. Some other notable features are armored trucks left by KDS and grow beds.
In contrast to all other environments, some typical elements found in every expedition have a unique design here, namely the doors, ladders and the zone/area labeling on the walls. Terminals are surrounded by a few additional lamps, making them more visible across the larger rooms. Plants and moss can seen covering large parts of the walls and floor. Some locations have a small layer of water covering the floor, resulting in special step sounds when traversing them.