Question

which area does sheet and gully erosion takes place

Answer 1

Hill slopes are prone to sheet erosion and rill erosion. The amount of hill slope erosion largely depends on how the land is used.
Sheet erosion occurs when a thin layer of topsoil is removed over a whole hillside paddock—and may not be readily noticed.
Rill erosion occurs when runoff water forms small channels as it concentrates down a slope. These rills can be up to 0.3m deep. If they become any deeper than 0.3m they are referred to as gully erosion