A river that remembers

Rill

Three storms. Five gardens. Six drops each.
Dig a little channel. The river will help deepen it. Later, it may refuse to go anywhere else.

Water moves left → right along the links. Number = bed height.
Blue = water route. Gold − = erosion. Dashed bed = rock bottom.

Select a channel bed

Choose a circle to inspect it before digging. Lower outlets attract water.

How this little river works

Start with two spades; after each storm, gain two more. A dig lowers one bed by one, to a minimum of zero. Unused spades carry over, up to four. Watching the first storm without digging saves a bigger repair for later.
Sixteen drops enter at the left. At each fork, only the lowest connected beds on the next terrace receive water. Tied outlets share it. Spare drops go to the straightest outlet, then the upper one.
After all water passes, any bed that carried four or more drops erodes by one. That change applies to the next storm. The source never erodes.
The preview shows the exact next route and predicted erosion. Select a bed and choose Preview this cut to see its whole hypothetical route without spending a spade. Garden totals stay actual. Dig commits it; Back returns unchanged. Rain is disabled while comparing. A cut can change an upstream route without changing garden delivery yet. After rain, the map shows the route that actually happened, on the newly eroded beds. Switch views to see the difference.
This is an abstract channel game, not a model of real rivers. A small playable experiment in repairing routes that earlier storms have deepened. One landscape; several ways through it.