The earth elements give us gravitational energy, its physical attributes create shapes, bodies, and structure. The earth element provides stability in a structure. One-fourth of your plot has a strong hold on the earth element. The part is half of the south and west direction.
The southern and western corners are extremely essential to harness the earth element. Vaastu defect is created in the area where the earth element is missing, for example, if basements are dug in southwest areas a big vaastu defect is created. Digging a well or an underground water tank in the south west of your plot could also cause vaastu defects.
If the building structure is made of the northern and eastern parts of the plot, and the southern and western direction remain vacant as a result the plot is deprived of the earth element. One should not give water slops towards the southwest. Heavy structure or elevation towards the southwest is prosperous. The earth element is an integral part of vaastu. Hence it has to be balanced.