I am looking for an adjective describing something that cannot be traversed because it is too deep.

We could not cross the river. The river was _______

The only word I can think of that comes close is "insurmountable", but this word usually describes something that cannot be crossed because it is too tall, and doesn't seem to fit for a deep river (or deep valley or deep hole, etc).

  • 'something' ?? You're looking for an all-purpose word that ignores the specific nature of the thing being traversed? Or do you mean river? – TRomano Apr 19 '16 at 21:58
  • @TimRomano I'm looking for a word specifying that the property of the thing that prevents it being traversed is its depth. I have clarified the question accordingly – Delyle Apr 19 '16 at 22:03
  • But what does the depth have to do with it, when a river is concerned? Boats can cross the deepest water. People swim in old quarries that are hundreds of feet deep. Are you thinking of being unable to ford the river? – TRomano Apr 19 '16 at 22:15
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    Seems to me that it's over your head/ – Hot Licks Apr 19 '16 at 23:15
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    I don't understand why you can't just state "because it was too deep"! – TrevorD Apr 19 '16 at 23:19

The river was unfordable


: incapable of being forded : impassable an unfordable river


We could not cross the river. The river was unfordable.

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  • Given that to ford means "to cross at a shallow place", I think this fits best. It feels odd to use it with anything but a river, though. – Delyle Apr 20 '16 at 18:42
  • While I think that is a great answer, a river can be unfordable also because of a current that is too swift/strong or other reasons besides simple depth. – Aethon Apr 24 '16 at 23:17

Impassable sounds right to me.


The first definition fits :

not passable; not allowing passage over, through, along, etc.:

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Impassable describes the fact you can't get across it, though it doesn't explain why.

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You have to say something like

They had to turn back at the canyon because it seemed bottomless.

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You could consider using the noun “depth” in a single sentence:

“We could not ford the river/[cross the valley] because of its depth."

1 a (1) : a deep place in a body of water ‘fish living at great depths’ (2) : a part that is far from the outside or surface ‘the depths of the woods’ (3) : abyss

2 a : the perpendicular measurement downward from a surface

3 : the quality of being deep


In your context and two-sentence example, you could also consider modifying the river’s/valley’s depth instead of the river/valley itself:

“We could not cross the river/valley. Its depth was too great."

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Unfathomable can be used in this context


Difficult or impossible to measure: the unfathomable depths
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