If you think it's flat, you've never pushed a wheelchair through the parks... nothing is horrible though, I wouldn't worry about it in planning as your not going to avoid them.
For those that really care though:
FLAT:
- "Parade routes" are usually flat if you need a break from the gradients, they are listed in the maps.
AK:
- the most with hills, mainly the long paths going between major sections of the parks.
- the queue to kali river rapids has hills on the winding path getting to the ride.
- tough to be a bug I think has a gradual ramp up to get out of the theater. it's winding and not much of a hill but not flat.
MK:
- The entrance into the park and heading to/from bus or monorail has a pretty good hill in both directions (you go down and back up both ways). From the boat its only a hill up into MK. The walkway from contemporary is the same as the bus.
- The back corner near splash mountain. (stay near the river for flat, but the exit of splash/train station/restrooms will be a hill up you can't avoid)
- The entrance into BTMR and Splash is a winding hill up 1 story.
- The path heading from pirates towards and passing pecos bill is uphill (in that direction).
- the parade route as it passes pecos bill has an incline heading towards splash. Stay near river for flat if heading to splash, if heading towards adventure land, go through pecos bill to the side entrance to avoid the uphill.
- inside space mountain but there is also a people mover that you just have to stand on.
- exiting jungle cruise has a ramp heading up.
- swiss family treehouse is a treehouse, you have to go up and down in the attraction into the trees.
- The path between barnstormers and space mountain is minor but not flat.
- the walkway from haunted mansion heading past peter pan is not bad but you do go uphill a little heading this direction.
- The back corner near the big top shopping (by the childrens cooling off section). there is some steps and a round about ramp. The up direction is leaving the corner heading elsewhere in fantasy land (towards dumbo)
- the ramps into the castle are a 1 story wheelchair ramp
- if your going into the castle, entering from the back is no additional hills.
- the paths on both side of the castle are also a 1 story climb, up direction is central hub towards back of castle.
Epcot:
- the land entrance is second floor and it's a 1 story wheelchair friendly long ramp to get up to the entrance..
- World showcase between uk and france when walking that direction has a bridge with a hill up towards to.
- The monorail is 1 story up, there is a ramp to get into it if traveling by monorail.
- The resort walkway leading up to and after the international gateway entrance.
- inside mexico has some ramps
- the dining in japan is all second story with ramps up
- inside american pavilion can be interesting but there is elevators and a friendly way to get in/out of the theater, just ask someone where to go and they will assist if really needed
Hollywood studios:
- doesn't really have much that really stands out but there is some changes in the areas surrounding the great movie ride. You'll find wheelchair ramps in areas that also have steps for people just walking or a more roundabout way for a less impacting way to go.
- inside star tours is a little up and down, however if disability related, they take wheelchairs and adult strollers a different way that is a straight walk in.
- There's a steepish hill heading up to Tower of Terror
TTC:
- Monorail switch epcot<>MK/resort loop: you have to go down and back up to switch between the 2 monorail tracks.
- If your driving in and taking the monorail it's just 1 ramp up to them.
- there is a slight hill when exiting the boat and heading towards your car/shuttle
resorts:
- you'll run into some at every resort depending on where your going, not as bad as the gradients in the parks. Generally they are the pathways near lakes and to/from bus stop.
- Wilderness lodge has a more noticeable incline heading down from the lobby.
- Animal Kingdom Villas near the main pool/entertainment area has a lot. Wheelchair friendly but they are there.
The first time I pushed a wheelchair though I found it annoying with all the little gradient changes. I felt it in my arms that week. Stroller wasn't too bad but my daughter was very light, different situations might be more challenging.