Objectives:
- To identify the barrier islands as part of the wetlands
- To show the value of the barrier islands to the wetlands
Although barrier islands, called spits in the northeastern United States, exist on all coastlines, they are most notable along the Gulf of Mexico and Atlantic coasts. They are the structures resulting from the movement of sediments by wind and the currents. The seaward side of a barrier island is usually a sandy, beach-like area (Fig. 2). This area increases and decreases in size with changes in seasonal wind and wave action which carries sand into and away from the sandy shore.
View Figure 2.
The area behind the beach is an area of dunes and then a mud flat or over-wash area created when the waves breach a low area of a dune (Fig. 3). The dunes contain plants that stabilize the system by trapping sand that would otherwise be blown away. The flat is wet and may be completely flooded during storm surges and extremely high tides. Beyond the flat is a salt marsh. These islands, as obstacles, slow down the waves and winds associated with strong storms and hurricanes that impact the coastal areas. They also provide a habitat for a many of the same species found along the coastal marshes.
View Figure 3.
Activity: (for elementary students)
1. Line students up on one side of the classroom (Fig. 4). They will represent an incoming wave or strong wind. Have them move as a group across the room and record the time it takes for them to cross the room. Next, set up a barrier of cardboard boxes, chairs, cement blocks, or boards (anything that is available and not dangerous to the students). This time, they must cross the room and go across the barrier. Record the time it takes for them to travel the same distance.
Discuss why it took them longer to cross the room the second time and how this phenomenon can positively affect the coastal wetlands. Ask the students about the type of organisms, plants in particular, that must inhabit the barrier islands. This might include ideas about how they are anchored so that they can withstand the wind and wave action as well as the fact that they are relatively small and shrubby.
View Figure 4.
Extensions: (for upper elementary and middle school students)
- Have students research and set up a demonstration to show why waves "break" as they reach the shore.
- Let the students find out why dunes with plants on them are generally larger than those without plants (give them a hint about carrying capacity of the wind at different speeds, if they need help). They may also research the formation of the barrier islands - explain why the sand was deposited there to begin with as well as how barrier islands "move."
