The difference in texture (sandy or clayey) and microrelief determined different soil formation (remember, that parent materials and relief are among the main soil-forming factors). Here you can see two typical soil profiles, collected from the natural levee (sandy clay, left figure below) and from the backswamp (heavy clay, right figure below). The sandy clay (sandy loam) has a good structure (many holes, which we will refer to as pores), and can therefore better filtrate surface water, and provides better conditions for soil macrofauna (which is recognizable from the many earthworms’ burrows). The clay soil does not have any pores since it is too wet and too firm for macrofauna to move around. Instead, it has lots of cracks which occur from swelling when the soil is wet and shrinking when it is dry.
Left: Sandy clay soil from the natural levee. Right: Heavy clay soil from the backswamps.