Ask-a-Dave's-Gardener: How to grow watercress, 1 by ballyshannon

ballyshannon wrote:
I looked up growing watercress online, and all of the entries are for container plants. I want to put it in the runoff channel around my house that keeps the rain from flooding my basement. Obviously I would have to water it when it's not raining.

How do I start the plants, and do I need to make a pond in the channel? It's mostly about a foot wide. The water flows pretty fast around it in hard rain.