News

Embracing the dynamics of shorelines

By: Eric Sparks / Published: Apr 04,  2018

Coastal areas are dynamic in nature, which means they are constantly changing. A fitting example of the dynamics of coastlines can be found by looking at historical, but relatively recent, aerial photos of Pelican Island on Dauphin Island, Alabama (Figures 1 and 2). The entire island has moved northward and became a peninsula over a relatively short period of time. You will also notice in those figures that the pier is now completely on land.

Pelican Island on Dauphin Island, Alabama, in 1992. Yellow outline is the main land masses in 1992 and the northern yellow mark is the location of the Dauphin Island Public Pier. Imagery from Google Earth.
Pelican Island on Dauphin Island, Alabama, in 1992. Yellow outline is the main land masses in 1992 and the northern yellow mark is the location of the Dauphin Island Public Pier. Imagery from Google Earth.

Pelican Island on Dauphin Island, Alabama, in 2015. Yellow outline is the main land masses in 1992 and the northern yellow mark is the location of the Dauphin Island Public Pier. Imagery from Google Earth.
Pelican Island on Dauphin Island, Alabama, in 2015. Yellow outline is the main land masses in 1992 and the northern yellow mark is the location of the Dauphin Island Public Pier. Imagery from Google Earth.

 

In a more developed area, the dynamics of shorelines can work for or against individual property owners. An example of these conflicting effects can be found on the West End of Dauphin Island (Figures 3 and 4). This example shows what the Dauphin Island shoreline looked like in 2000 and 2015.

West end of Dauphin Island, Alabama, in 2000. Yellow outline is the outline of the main land mass in 2000. The yellow arrows are pointing to houses that can be used as benchmarks for the next figure. Imagery from Google Earth.
West end of Dauphin Island, Alabama, in 2000. Yellow outline is the outline of the main land mass in 2000. The yellow arrows are pointing to houses that can be used as benchmarks for the next figure. Imagery from Google Earth.

West end of Dauphin Island, Alabama, in 2015. Yellow outline is the outline of the main land mass in 2000. The yellow arrows are pointing to houses that can be used as benchmarks from the previous figure. Imagery from Google Earth.
West end of Dauphin Island, Alabama, in 2015. Yellow outline is the outline of the main land mass in 2000. The yellow arrows are pointing to houses that can be used as benchmarks from the previous figure. Imagery from Google Earth.

Most of the changes you see are from the 2005 hurricane season, which completely reshaped Dauphin Island. As evident from the photos, several rows of houses were lost from the Gulf (south) side of the island, while the lots on the Mississippi Sound (north) side of the island doubled in size. This process occurred because sand on the south side of the island was blown or washed over to the north side of the island.

Another process that contributes to changing shorelines in our area is the prevailing direction of sediment and water movement in the northern Gulf. Generally speaking, nearshore water (and the sediment it carries) moves from east to west. This process is evident with you observe either side of the beach outfall pipes along Mississippi beaches (Figure 5). Typically, the eastern side of an outfall pipe (or any other similar structure) has more sand covering it than the western side. This occurs because the water flows from the east, slows down when it hits the pipe, and drops some of the sediment it’s carrying on that side (i.e., faster flowing water can hold more sediment). Once the water passes to the western side of the pipe, it doesn’t have much sediment left to drop, so that side erodes.

Biloxi Beach, Miss., 2017. Yellow arrow indicates general flow of water and sediment. Areas of abrupt shoreline change are caused by the presence of a beach outfall pipe and its interaction with the flow of water and sediment. Imagery: Google Earth.
Biloxi Beach, Miss., 2017. Yellow arrow indicates general flow of water and sediment. Areas of abrupt shoreline change are caused by the presence of a beach outfall pipe and its interaction with the flow of water and sediment. Imagery: Google Earth.

Getting comfortable with the dynamics of shorelines is something that property owners and managers struggle with. It’s unnerving to know that property is eroding away, especially if that property loss undermines the integrity of a structure, such as your house. When shorelines are changing in the backyard of most property owners, they often want to do something to stop it.

One common practice to address erosion is the installation of bulkheads. A bulkhead can be seen near the bottom left arrow of Figure 4. In that same photo it is evident that there is significantly more land being lost west of that bulkhead than east of it. Unfortunately, bulkheads and other structures can influence more than the property it’s installed on. As seen from this bulkhead and previous outfall pipe examples, it is very common for structures to contribute to erosion on neighboring properties. Additionally, these structures are associated with many negative environmental and economic consequences. Fortunately, there are more environmentally sound and cost-effective methods for shoreline protection called living shorelines. These methods incorporate natural materials, such as native plants, into the project to provide resilient, cost-effective, and environmentally friendly shoreline protection.

Comparisons of living shorelines to bulkheads.
Comparisons of living shorelines to bulkheads.

If you are interested in learning more, we do offer living shorelines education workshops in Mississippi and Alabama once or twice a year. The majority of these workshops are focused on homeowners, but there are some contractor workshops being planned for the near future.

If you are interested in being placed on the email list for future living shorelines workshops or have any questions, contact Eric Sparks, an assistant professor with the MSU Extension Service and coastal ecology specialist with the Mississippi-Alabama Sea Grant Consortium, at eric.sparks@msstate.edu or 228-546-1025.

Comments

comments powered by Disqus