Why do landscapers need to know the permeability of different types of soil?

for plants, it's a matter of stabilization and the soil helps stabilize the plant. Soils are generally made up of layers and soil quality often varies greatly from one layer to another. Before pond construction, it is important to determine the relative position of the permeable and impermeable layers. The design of a pond should be planned to avoid having a permeable layer at the bottom to prevent excessive water loss into the subsoil by seepage. I know there's lots of different types of soil but generally speaking, choose a lightweight for more fragile plants etc. I bought some planting soil that's super lightweight and works well for planting. It's not like dirt soil and is heavy and un-workable. I bought mine at Garden Delights Nursery.