Anything that you can put in close to the bank will help. The question is will it help enough to be worth your while?

Think about what they do around marinas at the big lakes...floating barges, if you will, that somewhat surround the boat docks. They diminish the waves considerably.

I have also seen electric pole "walls" at the ocean piers that really knock down waves. Basically, poles that are set verically in a tight row coming out of the water above the wave crests.

If I had a bunch of drain tile/pvc pipe works and nothing wlse to try (which is what I think you are talking about) I would consider running them parallel with the bank so that they are in water deep enough to just show the tops, but they really need to be anchored well. If they move with the waves they are not doing all that they can to stop the waves. I'm thinking cinder blocks, sacrete bags, T post, ect.

Disclaimer: I've not done this and would try a 20 foot section and observe before comitting to the full legth.

Fish on!,
Noel