Please note this is a tutorial, the pieces may scale up well but they are not a one size fits all pattern.
The waterfall is an extremely graceful type of drapery used in costumes depicting the mid-late Victorian era. They can be seen in many costumes in the stage production of The Phantom of The Opera and in movies such as Bram Stoker's Dracula (Mina's green silk dress when she first meets Dracula in London). They are even used in non Victorian costuming such as Star Wars (one of Padme's night dresses in Episode III.)

The question of how to make these has come up many times recently, and while I was happy with how I created the drapery for my first
Blue dress and
Hannibal drapery, it was trial and error. There must be an easy way to work out how your drapery is going to look.
And there is.

In my trial and error I had noticed that the top edge that is pleated and the curve of the free edge work to create the flare and curve of the base shape. So I decided to test with graph paper to show how this worked. I used this new method to drape my
Australian version Wishing Dress from Phantom of the Opera.
Since creating this page, I have refined the method. Still, this is a good start especially to see just how much fabric actually is required for the very flared pieces.
This basic method can work for any style of waterfall drapery you want. The method is the same but the repeating shape will be different depending on whether you want a greater or lesser number of folds and how flared or straight you want the shape to be.
The following two show how the drapery can be made to have few, shallow folds or many flared folds.

One can cut the striped fabric on the diagonal or across for different effects as well, these are simply examples to show how the different shapes can create different effects. I hope to show how I created the drapery for my first
Blue Dress which is cut from a narrow rectangle in the centre and triangular pieces down at the sides, cut on the bias. I also hope to show how to cut the apron and pannier drapery as well.