To remove an obstruction (physically or figuratively)(verb)
Wiktionary.org : Text is available under the Creative Commons Attribution-ShareAlike License
Use "undam" in a sentence
"And yet, Non omnem molitor quae fluit undam videt, the miller sees not all the water that goes by his mill: no doubt, but, as in our days, these were of the commonalty, all the great ones were not so much as called in question for it."
"The caterpillar had thoughtfully recovered his pack, which lay nearby, apparently undam-aged."
"But the word was not yet spoken which was to undam the pent-up torrent, and bear down with unrelenting vengeance upon the now exulting columns of the enemy."