| 4th edition generally uses a trap replacement theory. The stats and experience rewards are typically balanced around the idea that they should replace a monster of the same level. So you might, for example, have traps working alongside monsters in a single encounter. You can also create an encounter that revolves around traps, although you must be careful about this one. There is an example of an all-trap encounter in Keep on the Shadowfell, and it works fairly well, other than the relative difficulty of disabling the traps being very high and the general danger level of the traps being very low (and easily circumventable).
Hazards and "natural" structures tend to follow the same rules as traps, but also make great opportunities to litter the dungeon with strange diversions. There's nothing wrong with having a locked door or a crevasse that is easily overcome by the PCs with just a few checks. Even if it ends up being trivial, it may end up diverting the flow of the game a bit. Plus you can create some very satisfying moments when the PCs, for example, cook up an idea to "surf" off the edge of a cliff on a tenser's floating disk to get an extra 5 feet of height, holding a rope, with the intent of making the jump and helping everyone else across.
Really, static hazards give PCs who are well-versed in rituals a real opportunity to shine, so don't be afraid to pepper them in. | 
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