Do you know what a Slough is?

While driving down to Cannon Beach this morning, I kept seeing signs on small bridges along the coast with the word Slough in them. I knew it had something to do with water, but I wasn't sure how it is different than a creek, swamp or river.


Definition of Slough:
1. An area of soft, muddy ground; swamp or swamp like region.
2. A depression or hollow, usually filled with deep mud or mire.
also slue.
3. A stagnant swamp, marsh, bog, or pond, especially as part of a bayou, inlet, or backwater.
4. A state of deep despair or moral degradation.