Canal cross-section in cutting and filling

A canal in partial cutting and partial filling has its bed below ground level and its banks built up above ground, using the excavated soil.

          b                       b
        |----|                  |----|
   Bank_______           _______Bank
   top /    \  FSL ~~~~~~~~~~~  /    \ outer
      /      \ ___ free board /      \ slope
 ----/--berm--\_______________/--berm--\---- G.L.
 outer         \  full supply  /
 slope          \   depth     /
                 \___________/ bed
                    bed width B

Labelled elements

1. Bed (bed width B): the bottom of the canal.
2. Full supply level (FSL) and full supply depth (FSD): the design water level and depth.
3. Side slopes: typically 1.5H:1V in cutting and 2H:1V in filling.
4. Free board: the vertical distance between the FSL and the top of the bank (0.5-1.0 m).
5. Banks: embankments on both sides. The top width is 1.5-3 m for ordinary banks; the service bank, which carries the inspection road, is 5 m or wider.
6. Berm: a horizontal strip between the inner toe of the bank and the top edge of the cutting. It gives stability and reduces seepage, and is usually about 0.5-1 m wide (wider in deep cutting).
7. Ground level (GL) and borrow pits/spoil banks beyond the berm.
8. Hydraulic gradient (seepage) line: drawn from the FSL through the bank at a slope of about 4H:1V to 6H:1V (flatter for larger canals). The bank must be wide enough to keep this line covered by at least 0.5 m of earth at the outer face.

When the cutting equals the filling, the section is economical (balancing depth).