Impeding Effects slow the victim's movements or otherwise make them difficult. Caltrops, for example, can potentially cause damage, but this can be avoided if the victim slows movement to avoid the tiny spikes. Marbles or an icy surface either slow movement or introduce a risk of falling. Waist-high water slows movement, but has no risks unless the victim is knocked unconscious. Most Impeding Effects depend on a Solid or Liquid Material Effect, so detection is pretty much the same: typically, Vis/S to spot a shutter or valve that releases the caltrops, marbles, or water, Aud/S to hear them as they rumble or pour down the pipes. Damage-causing traps aimed specifically at the legs can have an indirect Impeding Effect as well, and may have entirely different chances and procedures for detection. A rotating floor or conveyor belt, or a trick staircase that turns into a slide, uses structural elements to impede movement and thus might be a little easier to notice, but difficult to avoid or disable.
Repositioning Effects change the location of the victim in some way. Chutes are Repositioning and Diverting traps, covered pits are Repositioning and Blocking traps. Repositioning Effects based on Solid Material Effects often cause damage as well (log attached to ropes that acts as a ram, causing 1d6 damage and knocking victim to one side;) those that depend on liquid or gas usually involve a blast of fluid and are less likely to cause damage.
There's a theoretical third type of Motion Effect; instead of reducing movement, a trap could increase it. I can't think of an example of this or how it would be useful, unless you want to include the trick staircase that turns into a slide which does not cause an immediate drop, but instead forces victims to choose between moving at double speed with a risk of falling, or half speed with no risk. Another theoretical example could be a canal with a gate that can be opened to increase the waterflow, making it difficult to reach a particular disembarking point and instead hurtling the victim's raft over a waterfall; however, that might be better classified as an Impeding and Repositioning Effect.