Soil drainage is defined as follows:
- Poor drainage: Water table <0.5m below ground level
- Moderately poor draining: Water table >0.5m below ground level
- Moderately free draining: Water table <1m below ground level
- Free draining: Water table <1.5m below ground level
Good soil drainage is important for tree species that don't like to get their "feet wet". Some tree species thrive in wet soil conditions and high water tables, whereas other species require free drainage, i.e. soils that drain away water and do not become saturated. Water tables tend to be at their highest after heavy rain, but quickly subside where drainage is good.