Coastal Loss Series, Part Three: The Role of Diversions in Rebuilding the Coast

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

Diversions are a large part of Louisiana’s Comprehensive Master Plan for a Sustainable Coast and one of the most effective options for enhancing long-term sustainability of existing wetlands.

Many of our waterways have been controlled and redirected, curtailing their historic patterns of overflow, natural course changes, and flooding—and thus restricting their ability to distribute sediment over the coastal plain. Diverting the flow of fresh water through coastal areas can build new land while effectively combatting saltwater intrusion. Diversions mimic the natural river process of depositing nutrients into wetlands. Why pay to mechanically move sediment when the river will do it for us naturally?

Unfortunately, diversions do come with some trade-offs.

It’s not a fast fix. It can take decades before the slow process of land building gives coastal communities any appreciable storm protection. In the short term, abrupt changes to salinity will impact fisheries, especially oyster fisheries.

The influx of excess nutrients may weaken root systems of marsh plants and facilitate the spread of invasive species like Water Hyacinth and Giant Salvinia, and there is the possibility of increased flood risk to coastal communities.

Finally, while salt marshes can take some fresh water, fresh water wetlands cannot take salt water without sustaining damage. Fresh marsh systems are susceptible to salt damage when low river levels keep diversions from flowing as happens in late summer and fall.

What do you think? Are the trade-offs and potential risks of diversion programs worth the value they have in rebuilding land in coastal areas? The benefits are the risks are both real, and our vanishing coast may hang in the balance.