hon. Head Designer
The source will be a big glacier, more water is joining from a side river that has two more glaciers as source.maybe the main source could split into multipe 2-3 wide block falls that then rejoin at the bottom of the falls, that way the source would be realistic, in the volume of water and the 2-3 block width would make the falls seem taller
There are many rivers throughout middle-earth that have fords and arent small streams: Sarn Ford @ Brandywine, Bruinen Ford, EntfordAlways thought nimrodel was just a small 2-3 block wide stream, since it was described as being fordable. Also, having it as a stream might allow nicer overall feelings, making the falls seem taller etc.
The shape will (most likely) be 3 falls after each other; they dont have to look tall.