You can't take the dam apart with your bare hands.
You'll need to use tremendous force.
Or at least create a tremendous force.
An explosion would be in order here.
To create an explosion, what would you need?
Something explosive and something to create a spark.
Why don't you find some?
Where can I find gunpowder?
To blow up the dam, you need to involve the gunpowder.
Place the gunpowder on the dam.
Now, there are two different ways to create a spark.
Think back to campfires or to frying ants on the sidewalk.
Method One (Frying Ants)
Method Two (Campfires)