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How Will Dredging Impact Sea Level Rise?

How Will Dredging Impact Sea Level Rise?

This post is by Dr. Jeremy Stalker.  Jeremy is an Associate Professor at Jacksonville University in the Marine Science Research Institute.

Dredging Will Accelerate the Impacts of Sea Level Rise

I will always support responsible, well thought out development for our city. I also support ideas that have forethought, looking into the future and using the best science to guide decisions. The proposed dredging of the St Johns River does not fit these criteria.

I have been studying hydrology and sea level rise in North Florida for 6 years and in South Florida for 12 years. The scientific analysis presented by the Army Corp of Engineers to estimate the physical impacts in the river are incorrect, incomplete, and seriously flawed.

Estuaries like the St. Johns River are dynamic systems that change in temperature and tide with each season, tide and storm. These systems and the plants and animals that live in them are well adapted to these changes. They can even withstand extreme events of high temperatures and high salinities for short periods of time. The analysis of the proposed dredging ignores the steadily increasing rise of sea level and its impacts. This plan uses an exceptionally low rate of sea level rise that is not supported by any scientific observations currently being collected.

Sea levels are rising, and in most places accelerating. Worldwide, flooding events caused by the regular high tide, often coupled with normal rainfall are becoming more and more frequent. You really only need to go down to St. Augustine at a high tide after a summer rainstorm to see water backing up into the streets. At times, we also see this happening in low-lying areas of Jacksonville, like San Marco and Riverside.

This will become more and more common in our coastal cities, and our cities connected to tidal rivers. This higher sea level will push saltwater farther up the river. The dredging will accelerate this salinization process by increasing the volume of area the seawater can enter through.

It will push salty water deeper into tributaries and further up the mainstream of the river. This will also increase the length of time the plants and animals will have to withstand higher salinities. The likely increase in freshwater withdrawals from the river upstream in Central Florida will only exacerbate this problem. These kinds of extended, extreme occurrences have led to sea grass die-off events in both Biscayne and Florida Bays. Plants and animals that depend on brackish conditions will find their habitat diminished.

The rise of sea level isn't going to go away. Even if we begin limiting the causes of ice loss, the system will move towards higher levels for centuries before slowing down.

I hope our regulatory agencies will use sound science, and be honest about the impacts so we can make good, informed decisions. Ignoring the rising seas and their effects on the modeling is short-sighted, simply pushing off the problem to our children and grandchildren. We need an honest assessment of the environmental impacts of the dredging, and only then can we really weigh the cost and benefits.

Click here for more information about the proposed dredging of the St. Johns River.

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