Land gains and losses become more complex when humans begin to alter the landscape. Land is gained by filling in marshes for agriculture, development and road construction. Land loss has occurred by damming the Mississippi River to prevent it from changing course. No new delta lobes are created. The levies, built for coastal storm protection, also prevent flooding from the river, which reduces sediment deposition through overland flow.
Subsidence occurs as a result of ground water, oil and gas extraction.
Subsidence is also a product of soil compaction from road construction. Marshland is impounded for agriculture and aqua culture. Impoundment is the process of flooding shallow freshwater marshes, destroying natural vegetation and creating open ponds. Finally, canals are dredged for oil and gas extraction and exploration. The primary cause of wetland destruction in the Louisiana marshes comes from the construction of canals.