Cascade is very similar to UDK's cascade (at least right now). Here's a tutorial I made last year for making rain in UDK. I'm planning on making a new one soon, but for now this might do the trick for you. You can now achieve far more realistic water effects due to pbr in UE4 so I should probably remake the tutorial here…
Everyone's blockouts are looking nice. @Zockey - I'm really looking forward to your final result after the Buddhist temple you did. Very well done! Here's my blockout and if anyone's interested I put up a quick tutorial on taking high res screenshots in UE4. I can only hope it's helpful to someone…