Saltwater intrusion is particularly dynamic in coastal Dade County because of the high permeability of the Biscayne aquifer, because of the good interconnection between canals and the aquifer, and because of the seasonal rainfall. The problem is accentuated as urban growth continues to encroach on inland wetland areas which results in lowered inland water levels. This lowering reduces the seaward freshwater hydraulic gradient and the freshwater head at the coast, both of which govern the intrusion of saltwater.