ShallowWaterRiver simulation does not initialize in Unreal Engine 5.7.4

General Issues and Bug Reporting (Unreal Engine)
1

Summary

Summary

The ShallowWaterRiver simulation does not work in Unreal Engine 5.7.4.

I can successfully place a WaterBodyRiver in the level, and the standard Water system works correctly. The river mesh is rendered, the water material appears normally, and all Water components behave as expected.

However, the ShallowWaterRiver simulation never starts.

When I press the Reset button on the ShallowWaterRiver actor, absolutely nothing happens. No simulation is generated, no ripples appear, no flow is calculated, and the river remains completely static.

I also tested the following:

  • The Niagara systems compile successfully.
  • There are no Blueprint compile errors.
  • No runtime errors appear in the Output Log.
  • The Render Targets are created correctly.
  • The built-in sample level WaterFluidSimtestShallow works perfectly.
  • The problem only occurs when creating my own level using WaterBodyRiver together with ShallowWaterRiver.

It appears that the simulation is never initialized. The WaterBodyRiver renders correctly, but the shallow water simulation itself never begins, even after pressing Reset or starting Play mode.

This looks like a regression or bug specific to Unreal Engine 5.7.4.

What Type of Bug are you experiencing?

Simulation

Steps to Reproduce

  1. Create a new empty project in Unreal Engine 5.7.4.
  2. Enable Water and Niagara Fluids plugins.
  3. Add a WaterZone.
  4. Add a WaterBodyRiver.
  5. Add a ShallowWaterRiver actor.
  6. Link the ShallowWaterRiver to the WaterBodyRiver.
  7. Press Reset in Simulation Section

Expected Result

The shallow water simulation should initialize automatically and simulate water flow inside the river.

Observed Result

No simulation starts.
No water movement is generated.
The InitializeShallowWaterSim event appears never to execute.
No useful runtime logs are produced.

Affects Versions

5.7

Platform(s)

Windows

Additional Notes

The sample level “WaterFluidSimtestShallow” included with the engine works correctly.

The issue only occurs when creating a new map using WaterBodyRiver + ShallowWaterRiver.

Niagara compiles successfully.
Render targets are created.
No Blueprint compile errors are present.

This appears to be a regression in UE 5.7.4.