Dredging: The Real River Monster


Recently, the Jacksonville City Council approved $110 million for JaxPort to continue deepening the St. Johns River from 40 to 47 feet. Despite the lack of any real mitigation to offset the impacts, the Army Corps of Engineers and JaxPort told the Council and the public not to worry – no harm will come to our river. In the slim chance they have erred in their analysis, the Corps will be monitoring the after effects of the dredging and will take appropriate actions to address any unintended consequences.

So, it sounds like everything is under control, and we can move on, right? Not so fast.

Decades of dredging the river to allow for bigger and bigger ships to access Jacksonville’s port has taken a toll on the health of the St. Johns, while making Jacksonville and surrounding communities more vulnerable to storm surge and flooding. The current dredging project will only cause additional harm and exacerbate the accelerating impacts of sea level rise.

Even the Corps’ own analysis anticipates saltwater intrusion from a deeper channel will adversely affect hundreds of acres of wetlands, trees and submerged aquatic grasses, while storm surge height will increase by up to 9 inches in parts of the river. In addition, water levels in the river may increase by up to a whopping 12% during “high frequency” storm events. If we learned anythingfrom the historic flooding that resulted from Hurricane Irma, inchestruly do matter.

Yet, the Corps determined these impacts to be insignificantand declined to conduct further analysis or provide meaningful mitigation.

However, the biggest problem is not the Corps’ disregard for the significance of these impacts. The problem lies in the thoroughness of the studies and the efficacy of the models used toconduct the analysis.

Despite projecting a much smaller dredging-induced storm surge for Charleston, the Corps inexplicably required a more exhaustive flood analysis, while dismissing the need for a similar study in Jacksonville.

Corps has also acknowledged the limitations of their own models, stating “actual conditions will deviate from those used to drive the models. These deviations introduce additional uncertainty in the models’ ability to predict future conditions and impacts.”

An independent expert panel that reviewed the Corps’ work, concluded, “The analysis and presentation of salinity results provide an incomplete understanding of the impacts of channel enlargement.”

In other words, it is likely that the impacts from dredging may have been underestimated.

We also must acknowledge that the Army Corps has a long history of underestimating the environmental impacts of its projects. Look no further than Miami to understand the consequences of these miscalculations. A study released last year concluded that the Army Corps of Engineers vastly underestimated the amount ofcoral impacted by the dredging, finding over a half million cora lwere killed and dredging impacts may have spread across more than 15 miles of coral reef tract.

To make matters worse, the Corps denied culpability, despite vast areas of dying coral smothered in sediment. Thanks to a lawsuitby the Miami Waterkeeper, the Corps finally agreed to replant someof the coral that was destroyed.

Monitoring the damage that is obviously attributable to dredging does not provide a guarantee of corrective action or accountability.

We raise these concerns not to disparage or discredit the Army Corps and certainly not to call into question the integrity of the many talented and dedicated public servants who work for the agency.

We do so as a reminder the St. Johns River is too complex, the models too imprecise and imperfect, our knowledge too limited, and the potential consequences too great to blindly accept the Corps’ analysis or that of any agency as an absolute, especially when they leave us with no room for error.

There is too much at stake if our analysis proves to be imprecise or deficient and we fail to account for impacts of our actions – the future health of the St. Johns River hangs in the balance.

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