The following statements (S1, S2, S3 and S4) pertain to the type of canals based on alignment. Select the correct statement/s.

S1: A ridge canal can irrigate command areas on one side of the canal only.

S2: A contour canal can irrigate areas on both sides of the canal.

S3: A ridge canal requires very less number of cross drainage works.

S4: Side slope canals are aligned roughly parallel to the natural drainage of the region.