(of ground, water, conditions, etc.) hazardous because of presenting hidden or unpredictable dangers.
Merriam-Webster Online Dictionary
treacherous (adjective)1.
characterized by or manifesting - treachery perfidious
2.
a) likely to betray trust - unreliable a treacherous memory
b) providing insecure footing or support - treacherous quicksand
c) marked by hidden dangers, hazards, or perils faithless