gulch (n.)
- abysm
- abyss
- aqueduct
- arroyo
- bed
- breach
- break
- canal
- canyon
- cavity
- chap
- chasm
- check
- chimney
- chink
- cleft
- clove
- col
- crack
- cranny
- crevasse
- crevice
- culvert
- cut
- cwm
- defile
- dell
- dike
- ditch
- draw
- excavation
- fault
- fissure
- flaw
- flume
- fracture
- furrow
- gap
- gape
- gash
- gorge
- groove
- gulf
- gully
- headrace
- hole
- incision
- joint
- leak
- moat
- notch
- nullah
- opening
- pass
- passage
- race
- ravine
- rent
- rift
- rime
- runnel
- rupture
- scissure
- seam
- slit
- slot
- sluice
- spillway
- split
- swash
- tailrace
- trench
- valley
- void
- wadi
- watercourse
- waterway
- waterworks