Learn how to create a flowmap using the new Flow Map tools in Houdini. You will see how control the flowmap velocities by using terrain geometry, a curve, and also how to manually comb it if you wish for more specific control. Then export the mesh geo, bake out the flowmap, and assemble your riverbed in Unreal Engine.
Tutorial by Andreas Glad - - - - - - - vimeo.com/partikel
Download scene files here - - - - - - sidefx.com/tutorials/flowmaps-houdini-for-games