Mounding Beds for Depth, Drainage, and Capacity. Oval mounded bed encourage run off of access water on the beds, into the rows, and out of the garden or collected in the row where it will get absorbed. Double Dug Mounded Bed Drainage Duble Dig to Break Up the Under Lying Compact Soil Once You Double DIg, Use Shovel to create Rows and Beds by turning row into bed one way, then the other way in two passes.