A dredging ship digging sediments from the bottom of a channel (NOAA)

Hurricane season is scary for those living in vulnerable areas. They cause property damages, drastic changes to livelihood, and in many cases, loss of loved ones. Hurricane Sandy devastated the communities of Long Island in 2012 causing major flooding and leaving hundreds of thousands without power.  It is one of the most costly storms in US history.

With hurricanes becoming more frequent, this year being one of the worst on record, and storm surges becoming worse with climate change, it seems that the devastation these storms bring is unstoppable. But is that true? Are sea level rise and climate change the  only factors contributing to storm surge intensity?

The natural environments of storm prone areas help reduce the impacts of storm surges. A recent study explored the ways human impacts in these areas worsens the severity of storm surges. Wetlands provide buffer zones for inland damage resulting from natural disasters such as cyclones and their following storm surges; their removal for industry and communities is a common example of human interference amplifying the impacts of natural disasters.

  A recent study from R. Familkhalili and their group of researchers explored the ways human activity impacts the severity of storm surges. The study models surge events to determine how storm surges behave in an estuary, areas where fresh water bodies meet the ocean. 

Maritime transportation is an essential part of coastal economies. To keep ports open to ships dredging water bodies is often necessary. Dredging removes sediments to ensure the safe passage of boats and ships through canals and harbors. Not only does dredging provide work for those directly involved in the process, it also helps open up coastal communities to maritime trade and other opportunities that bring economic stability to these areas. Economic activity based in the Long island Sound is estimated to produce $9.5 billion per year, and this economic activity is heavily dependent on dredging. While dredging is good for boats, it can be devastating for estuaries. 

A photo of coastal storm surge flooding in New Jersey (Scott Anema/ New Jersey National Guard)

More dredging means a greater water depth, and higher storm surge heights. Changes to the depth of estuaries can have an impact on tides, circulation, and transportation patterns. This means that higher storm surges from sea level rise will only be amplified by dredging. 

Familkhalili simulated multiple surge events on estuaries to examine the interaction of dredging and storm surges. The simulations essentially create a model estuary where conditions of  storm surge or estuary can be changed. The results of this study found that more channel deepening, resulted in more frequent and higher waves and deeper waters during surge events.

Different areas of estuaries will be affected differently by storm surges. Storm surges were placed into two categories: those with short time scales and those with long time scales. The scale depends on the heights of the surge waves. Long time scale surges have small waves while short scale surges have high waves. Surges from short time scale storms affect the mouth of the estuary while long time scale surges go farther into the estuary. This means that different parts of an estuary are more vulnerable to flooding from different types of storm surges. 

    The flood risk to estuaries worsens because of human activities such as dredging. We may think that a deeper channel may act as a trap or buffer for surge waters, but this is not the case. The deeper channels that are left from dredging allows for higher storm surges to reach further into estuaries. Sea level rise continues to worsen these issues. 

This study can help save at risk communities. While dredging brings economic opportunities to communities, dredging is not just about shipping, it is about community resilience to powerful storms. The attention brought to the implications of dredging and other activities that deepen bodies of water alert communities and their officials of the problems that they face from storm surges and what is causing those problems.  

Storms that cause surges are becoming more frequent and more intense as the climate is changing. When the areas that soften the blow of these storms are being unnaturally altered, that line of defense goes away. For estuaries like the Long Island Sound, maintaining the integrity of the surrounding ecosystem is key to protecting surrounding communities. As the activities that change those spaces simultaneously make natural disasters more dangerous, we need to become more aware of these effects to be better prepared for its impacts. This study begins to explore these impacts, and looking to the future, as more research investigates this subject, we can better prepare for the impacts of storm surges.