Ext. power USB hub causes Because a USB device was drawing too much power

If you have another mac try them on it if not you can buy 2 external enclosures and take the wds apart and put the drives in there. if they are the small portable wd drives they have a usb port instead the normal adapter card it wont work

If what ljonesj doesn't work, there are services which can recover data from a damaged drive. They are not cheap, but might be worth it to you.

Hopefully it only knocked out the circuitry in the case and not the hard drive....buy an empty external USB HD case (2.5" or 3.5" depending on the size of the drives in your WD cases - generic cases are fairly inexpensive), take the drives out of the WD cases and insert into the new case one by one. See if the drive(s) will work in the new case.

It may not be as bad as you think.

I would try plugging them in one at a time to a powered USB port on your computer, not via the powered hub. If the disk is recognised by the OS but there is no data on it or it reports it as being unreadable, then you may have damaged the filesystem (thought this is fairly unlikely).

If it doesn't work, you have two courses of action available to you and which one you take will depend on how important the data is to you.

1. Try to fix things yourself, this is possible if the error is a logical one rather than a physical one, but requires you to know what you're doing

2. Send it to a professional data recovery company. Good data recovery companies can work wonders. If it's simply a controller failure (which is most likely if you've had some kind of power problem) they should be able to replace the controller and recover 100% of the data. Even if the disk has failed at the physical platten level, they can often get some if not most of the data off. However, these services aren't cheap, recovering data from a controller failure costs about £300 here in the UK and the prices go up depending on how complex the recovery operation is. Stuff that involves opening the disk in a clean environment obviously gets very expensive, but it depends how important the data is to you. Most reputable companies will do a free estimate, but don't be tempted to skimp, use a reliable, professional data recovery company, the low cost ones are as likely to render your data irrecoverable as they are to recover it.

One important lesson - if the data matters to you, back it up. That's probably preaching to the converted (now), but it's as true as it ever was. The cost of backup is trivial compared to the cost of recovering lost data or the trauma of losing it altogether if it's not recoverable.