Contour Terraces
Contour terraces have point rows and grassed waterway outlets
that follow the lay of the land.
Parallel Terraces
These BMPs are so named because they are constructed parallel
to each other, and where possible, in the direction of field
operations. Parallel terraces eliminate the production losses
associated with point rows and minimize the interference to
farming operations when spaced at multiple widths of planting
and harvesting equipment. A more specialized form of the
parallel terrace includes the parallel tile outlet terrace.
Parallel Tile Outlet Terrace
Terraces that are constructed in parallel and discharge runoff
through subsurface drains are known as parallel tile outlet
terraces. With PTO terraces, water that is stored behind a
terraced ridge is discharged through a surface inlet into a
subsurface drain.
The surface inlet, which is called a riser, has a restricted
section to control the discharge rate, causing some of the
runoff to be temporarily stored. This storage period is long
enough for the sediment to settle out of the water, but not so
long as to damage the crops.