Coastal Loss Series, Part One: How does coastal erosion happen?

Coastal wetlands

This is the first of a four part series focused on Coastal Loss and presented by the NOTG Conservation Committee.

A coastline—any coastline—depends on the interplay of water and land. In coastal wetlands, vegetation also plays a role. The earth, or soil, depends on the plants that depend on it—as when the roots of wetland trees or grasses hold together sediments and soil fed by fresh water.

When saltwater replaces fresh, native trees and grasses cannot survive. When they go, so go their root systems and the sediments and soils they held, washed away to the Gulf. Many causes of coastal erosion are related to saltwater intrusion made possible by canals and “improvements” made to facilitate navigation combined with other improvements that cut off the flow of freshwater through the wetlands. Causes of coastal loss include:

  • Subsidence/compaction-a natural process but in nature a river would constantly add sediment back to the land mass
  • Hydrologic modification-building canals, roads, and railroads which cut off fresh water
  • Canals cut for cypress logging and then later for oil and gas extraction in the late 70’s
  • Straightening rivers and bayous for navigation, making saltwater intrusion easier
  • Sea level rise
  • Wave erosion causing shoreline retreat
  • Nutria herbivory