runoff block only visible during rain (flowing water during rain)

I live in Hawaii, where fairly short yet sheer cliffs are all around. During the rain, waterfalls are everywhere, as the rain comes from the mountain-tops and pours down the sheer cliffs. However, these mountains are actually very small, which makes them very close at all times, making the waterfalls spectacular. 

Because of the verticality of minecraft, builds in minecraft are much like these hawaii mountains, where they are tall enough to fill your view, but not particularly far away. I think if it were possible that just like at night lights can make the night worth it, If there were "flowing runoff blocks" that players could place and that during rainfall in the game would create a flowing water effect, this would make the rain something to look forward to in a way it just isn't right now.