The Flow Restructure device is a powerful modeling tool that makes your terrain hydrologically valid — it makes sure that water placed anywhere on the terain will drain off the map or to your existing water systems. Within the output terrain, every data cell has at least one outlet lower than itself, so that water will always flow and never pool.
The Restructure device does this by simultaneously carving through ridges and applying sedimentation in basins until the terrain drains properly. It attempts to make the minimum amount of changes necessary to make your terrain drain.
The original terrain does not drain 
Flow restructure to the rescue!
Another way of thinking about this is that it removes all locations where a lake would grow from your terrain. Doing this might make some major changes! Mountain valleys are raised, rivers cut through ridges, and more. Because of this, even if you have no plan to display or use water on your terrain, there are other benefits like:
- Ensure mountain valleys are higher than lowlands
- Improve erosion quality with proper drainage basins
- Connect different valleys together in a natural manner
How to Use
The following short video shows how to use the Flow Restructure device in concert with the Create Water device to create a river system:
Inputs
- Primary Input – Connect the terrain you want to modify
- (Drainage Input) – Connect either an existing water system or a mask to indicate what areas of the terrain to drain water into
- (Synthesis Guide) – For the “Synthesis” mode, supply a mask indicating what areas should be valleys and what should be cliffs.
Parameters
The Restructure device should work with a minimum of tweaking, but you may wish to adjust the following parameters:
Ridge Carving
This parameter allows you to prohibit or allow Restructure to cut through ridges to drain adjacent drainage valleys. Higher values provide a stronger ridge carving effect.
Basin Restructuring
Provide a characteristic angle that drainage basins will take on. This value generally works best at 0; set to a small value to produce more steep gradients. You may want to do this for either visual purposes or technical ones (such as ensuring a minimum gradient in-game for your water system, etc)
Drain-to
Control various combinations of whether water can drain to the map edge, the global ocean level, or existing water systems.
- Map borders and drainage mask – Water must either leave the map or enter a region you’ve supplied as a drainage mask
- Drainage mask – Water must drain into the pre-existing drainage mask (mask or water input) you supplied
- Map borders along drainage mask – Water must drain to a map edge, but only those areas where our provided drainage target intersects!
Operation
The method of operation of the Restructure device.
- Restructure enforces a hydrologically-correct terrain surface that water will flow down.
- Synthesize will if necessary create terrain entirely from scratch, subject to your input constraints. Synthesis mode is experimental and will change between versions!
Tips and Tricks
Flow Restructure will almost always be needed directly in front of a Create Water Device to create a draining terrain!
Add a Restructure To properly drain the terrain!
You can however also use it earlier in the network whenever you need to reshape an artificial terrain.
Limitations
This device may not work as intended when used in a tiled build.
Start the discussion at forum.world-machine.com