When Blaze use to dig, my dad would yell, scream, throw things to no end. It didn't help. Then mom decided to "improve" the landscape. Everyday Blaze would dig a hole, she would go out there, lay some waterproof fabric, pull some larger rocks around it, and put water in it. Blaze would come out the next day to his new favourite hole, and find the water. He'd pace around for a bit, then find a new spot to dig. He did this five times, then he stopped. He hasn't dug since.
He's also stopped the couch digging, but we have no claim to that. He was sneaky. He'd unzip the back of the cushion, dig out the back half of the foam, hide his rope toy or stuffed toy in it, then zip it back up. We had some lumpy cushions