The Terrain Slope operator can be used to add a slope (height gradient) to a terrain.
Grid names: terrain grids with matching names will be modified.
Operation: controls how slope values will modify existing terrain height values.
Gradient: controls the slope type. Radial gradients create a circular slope, linear gradients create a slope that rises/falls along a single axis.
Gradient curve: the curve allows you to control the interpolation of the slope (a 0-1 multiplier on the height value) from the beginning of the slope to the end.
Height: controls the overall height of the slope in world units.
Offset X/Y: allows you to offset the center of the slope along a particular axis.
Scale X/Y: allows you to control the overall scale of the slope, relative to the size of the grid.