Water power - why not?

So we've had the wettest 2012 since records began, so isn't it time we found a use for this water?

2 things - tidal power and Hydro-electricity.

So why don't we harness the tidal power? The tide goes in and out twice a day GUARANTEED.

Then all this water that fell on us, build some dams up in the hills and make it generate electricity as it flows out? You never know it might protect the valleys below.