Dead Flood of Dwfn Eir-Grøn

From publisher blurb:

Mini-Dungeon for 4–5 characters of levels 7–8

When a sacred dweorg festival is raided by the drow, with hundreds slain and even more enslaved, abducted, and turned into undead servitors, a deity weeps. When the divine tear becomes a flood that puts to rest the undead, the party has the chance to follow the legion of living dead on sturdy dwarven kayaks through the caverns, riding the Dead Flood of Dwfn Eir-Grøn.

The undead and their drow masters are stranded, briefly, but can the party prevail against a sheer endless legion of the living dead, punish the drow and rescue the few hardy survivors that remain?