Due to unprecedented public demand, here is the 'HOW TO' on building natural looking waterfalls and cascades with flexible liner.
BASIC PRICIPLES:
You must cut into the bank to make it look as though the water has the made the stream itself by cutting into the bank. The waterfall entrance into the pond is best at a sort of delta in the shape i.e. and outward curve.
The top of the waterfall must have a header pool. Also unless there is a clean drop to the bottom pool, it best to work in level, and at each level there is some sort of reservoir. In big cascades there is often the opportunity to add more water at these places as it cascades down to make an cumulative effect.
Always start from the bottom and work up to the top. If you see a perfect stone for a certain position, save it. 'Sill stones' and 'Waterfall facing stones' are particularly valuable. Stones that are shaped like the continents of Africa and India are very useful for in filling between larger stones.