The Unreal water system has support for rivers, which does this for you.
If you want to model the river yourself, you can use a spline and extrude geometry across it, which will generate flowing UV coordinates that you can then animate.
The Unreal water system has support for rivers, which does this for you.
If you want to model the river yourself, you can use a spline and extrude geometry across it, which will generate flowing UV coordinates that you can then animate.