Marine Issues on Daufuskie Island

In this project, we looked at erosion and marine issues.

To analyze erosion, we tracked the shape and size of the island from 1977 to 2023. To do this, we needed to be able to identify the wet-dry line. The wet-dry line is where the soft, light sand goes dark and hard, indicating the average position of high tide.

We traced the wet-dry line for different years to see how much sand eroded off of Daufuskie. Erosion and structural damage are typically caused by changing currents, king tides, and storms such as hurricanes. Structural damage can also be caused by storm surge, lightning, high wind speeds, etc.

Sea level rise is another issue for our island community. Sea level rise can cause damage to roads, homes, and other structures on Daufuskie. We mapped roads on Daufuskie that would be flooded at 1 ft, 2 ft, and 3 ft sea level rise scenarios.

Daufuskie Island is nestled between the major cities of Charleston, South Carolina and Savannah, Georgia, being more south towards Savannah, just west of Hilton Head. This means that Daufuskie is in the dead center of a subtropical area--meaning it is surrounded by muddy marshes and sandy beaches which support enough wildlife to easily outnumber its permanent residents.

Since Daufuskie is dead center of a sub-tropical area, and is an island, storms happen to be quite common. Warm waters make hurricanes and tropical storms more common and more intense. Even though a storm or hurricane may not make a direct hit to a location does not mean it does not do a lot of damage. Hurricane Matthew is a good example of this.

This year, the Atlantic Ocean has faced 12 months of record high temperatures. On average, it's been 2 - 3.5 degrees hotter than normal. The surface temperature of the Atlantic is currently as high as it typically is in August. These record breaking temperatures, when combined with the La Niña weather pattern from the Pacific, allow for a higher chance of tropical storm formation and higher chance of those storms turning into full-on hurricanes.  National Oceanic and Atmospheric Administration  (NOAA) has predicted 2024 will be the busiest hurricane season on record.

If you have ever looked at a soil map of Daufuskie you may have noticed its ridges. These are thin, noodle-like high spots on Daufuskie. These ridges are important to the local eco-system and flood prevention, as they drain water back into the creeks and ocean and provide wetter swamps. These ridges give us a bit of insight into how Daufuskie was formed. Daufuskie used to be a single, strip of land off the coast of South Carolina known as a "barrier island". Sediment then deposited along that barrier island, forming another right next to it. These barrier islands then joined together, and over hundreds of years of that process repeating, we have our modern Daufuskie.

Erosion is a natural process where storms, tides, and sea level change moves land mass. Erosion occurs when waves or storm surges take sand or land from the landmass and currents move the sand to another place.

After large storms, erosion can be drastic. But over time, the beach can replenish itself, bringing the sand that is under the water and offshore back up on the beach with the waves. This process doesn’t work though if there are too many storms in a short period of time or no sand offshore. That is why, sometimes, you have to take actions to protect the beach against the waves. Anti-erosion measures can include sandbags, rocks, or walls.

Zoom in to see differences between the wet-dry lines of 1977 and 2023

Monuments are permanent markers on Daufuskie that are used as reference points to track changes in the shoreline profile. The first beach profile survey was conducted in 1988.

As shown in these graphs, the largest change in land mass occurs from 1977-2009. That is because 1977-2009 is the biggest time gap. The most drastic change, with a smaller time difference, is 2011-2017. In between these 6 years, several powerful hurricanes hit the Eastern Seaboard, including Hurricane Matthew in 2016 and Hurricane Irma in 2017. Hurricane Matthew was one of the most destructive recent hurricanes for Daufuskie, even though it wasn't a direct hit. The sea wall was destroyed, trees were uprooted, and the island had to be evacuated. Hurricane Irma passed by Daufuskie as it was traveling inland. Some side effects of Irma were wind, rain, tree branches breaking off trees, etc. However, from our data, it doesn’t appear that Hurricane Irma directly impacted Daufuskie very much. 

The following maps show some of the areas of significant change over time on the island. By measuring the difference between the wet-dry lines of 1997 & 2023, we can compare actual square footage lost and gained.

Sea level rise refers to the gradual increase in the sea level over the years, which occurs when the amount of water in the ocean increases. Some things that contribute to sea level rise are glaciers and ice sheets melting. As sea level rise occurs, it causes coastal areas to flood and erode, especially during high tide or king tide scenarios. This can also affect our freshwater and destroy ecosystems as well as infrastructure. A prime example on Daufuskie is Driftwood Beach. 

The 1 foot to 3 foot scenarios show the rise of the ocean by the corresponding number of feet. Over the last 100 years, sea level has risen by 1 foot. In the next thirty years, it is expected to rise another foot. Therefore, the 3 foot scenario will be a reality around the year 2080. The rate of SLR is accelerating. 

Fort Pulaski is the nearest water level gauge to us. A water level gauge is a station that NOAA uses to measure the water levels at a specific location. Over time this water level record allows us to see how much the water has risen over time so we can get a sense of local sea level rise rates.

On Daufuskie, there are many roads that might flood with sea level rise. Examples of these include Old Haig Point Rd., River Pl., Outer Banks Trail, Freeport Dr., Shell Rake Dr., Cedar Cove Ln., Haig Point Rd., and Port Passage. Most of these roads also have alternate routes. Even though Old Haig Point Road is a main road, flooding is only projected to happen at the end of the road, so it may not be much of an issue. On the bright side of these sea level rise scenarios, Daufuskie Island retains much of its shape even with the flooding.

This sliding map shows the change between the 1 foot and 3 foot scenarios, showing how large of a difference there is between the two, and as you zoom in, shows how significantly the roads flood in the 3 foot scenario and even how decently they flood in the 1 foot scenario. The darker the shade of blue, the greater the depth of water. Zoom to see the differences more clearly.

The Calibogue Club in Haig Point is one of the areas on the island most dramatically affected in the 3 foot sea level rise scenario, as illustrated by the slider below

So, what did we learn? We learned that erosion can affect the sand dunes, shoreline, vegetation, and wildlife. We also learned that erosion on Daufuskie has caused roads to crumble and houses to become vacant due to being too close to the water. If you look closely at the wet-dry line from 1977-2023 you can see houses gradually getting closer to the beach over time and some are even now in the ocean.

We averaged all the changes in shoreline and saw that our ocean-side shoreline has receded 173 ft since 1977. Interestingly, we also noticed that not only has the shoreline receded, but also there are places that have gained shoreline since 1977, including Bloody Point and parts of Haig Point. Although the shoreline may have receded, the sand that is washed away sometimes ends up on other islands or other portions of our island.

We also learned that sea level rise can affect the island over time. If sea level rises 1 ft, we will see a couple of roads that are regularly flooded. If sea level rises 2 ft on the island, many more roads would be flooded. At 3 ft sea level rise there would be a significant difference in some areas. Our sea level rise mapping does not include potential flooding across the island from the rising water table.

Overall, our research shows that erosion and sea level rise are significant issues for the island, especially looking into the future. However, the 3 ft sea level rise models are still 60-80 years out. If we sit here and do nothing about sea level rise, portions of the island will look very different. For example the Calibogue Club in Haig Point would become Calibogue Club Island, a barrier island of Daufuskie. The good news is that Daufuskie Island's fate is not sealed. In this project we have identified areas of greatest change on the island and have been able to measure that change. It is now our environmental stewardship and responsibility to search and learn more about the actions we can take to preserve and protect our island.