The Coast in Motion
By Elizabeth King
Focus Question
How does the coast change? What causes these changes? What effect do man-made
structures have on the beach?
Activity Synopsis
Basic coastal processes and resulting geomorphology of a “typical” beach and barrier
island along the Atlantic Coast of the U.S., especially in SC, are modeled to demonstrate
the dynamic nature of the coast. This activity can be done in the classroom as well as on
a beach.
Time Frame
1 or 2 50-minute class periods
Student Key Terms
 longshore current
 spit
 sandbar
 scarp
 surf zone
 maritime forest
 salt marsh
 dune
 berm
 profile
 hurricane
 storm surge
 inlet
 ridge and runnel
 groin
 seawall
 revetment
 swash
 backwash
 littoral drift
Objectives
The learner will be able to:
 understand basic coastal processes and geomorphology
 model the dynamic nature of the coast
 model the effects that man-made structures have on the beach
----------------------------------------------------------------------------------------------------------------------------- --From COASTeam Aquatic Workshops: Oceans (grade 5); a joint effort between the COASTeam Program
at the College of Charleston and the South Carolina Aquarium – funded by the SC Sea Grant Consortium.
1
Fifth Grade Standards Addressed
Science Standards
IA5a; IA6a; IIIA1j
Background
Key Points
Key Points will give you the main information you should know to teach the activity.
 The beach is dynamic in nature, and is constantly changing.
 Longshore current provides the force for the most change to our coastline, by
moving great amounts of sand offshore and depositing them at opposite ends
of individual barrier islands.
 Winds, waves, currents, tides and storms are all natural forces that continually
change the beach. Human impacts such as seawalls, revetments, and groins
also change the topography of the beach.
Detailed Information
Detailed Information gives more in-depth background to increase your own knowledge,
in case you want to expand upon the activity or you are asked detailed questions by
students.
Wintertime is a wonderful time to walk on the beach, the section of barrier island
closest to the ocean. Summer crowds have thinned, and shells are abundant. There is
something about the beach that lures us back visit after visit. The beauty and
spaciousness attract us, but there is another aspect on the interface between land and
sea that we find intriguing: the beach is constantly changing.
A continual force working along our coast is the longshore current. This current or
mass movement of water (also known as littoral drift) generally flows from north to
south along the face of the beach. Littoral drift is the force that carries you down the
beach, away from your towel and sunscreen, as you swim in the surf. Just as it carries
you, this current moves tons of sand each year. In fact, so much sand is transported
along the front of the beach that geologists call this phenomenon a “river of sand.”
The longshore current tends to erode the north end and build up the south end of
barrier islands, a process that occurs daily little by little.
If you live near the beach you can watch it change seasonally. The larger waves and
stronger winds of winter carve sand away and give the beach a steep slope; often a
little sandy cliff will appear in the midsection of the beach. This profile is called a
“winter beach.” Much of the sand removed during the winter is stored just offshore
in the form of a sand bar. During the summer, climate patterns change and strong
winds calm. Waves reaching the beach are gentler and push the sand back onto the
front of the beach. The slope becomes more gradual as the beach flattens out. The
profile is now called a “summer beach.”
----------------------------------------------------------------------------------------------------------------------------- --From COASTeam Aquatic Workshops: Oceans (grade 5); a joint effort between the COASTeam Program
at the College of Charleston and the South Carolina Aquarium – funded by the SC Sea Grant Consortium.
2
A force that may bring instantaneous change to a barrier island is a big storm or
hurricane. The large waves associated with big storms can flatten yards of grass and
cover relatively stable dunes. The effects of a storm are magnified when the storm
coincides with a spring tide, a period of particularly high and low tides. Hurricanes
are usually accompanied by a storm surge, a large mound of water that may wash
over sections of a barrier island. Sometimes the surge carries sand and other debris as
far inland as the maritime forest or marsh behind the island. Occasionally the storm
surge will focus on a narrow section of the island, cutting a new inlet at that point.
Wind, waves, currents, tides, and storms are some of the natural forces that are
continually changing the face of the beach. It is this active landscape that we find so
alluring at the beach; there is something different to see each day.
Procedures
Materials
For Classroom
 Large shallow tray such as a wave table or child’s swimming pool
 Enough sand to make a sizeable pile (at least 1 5-gallon bucket full)
 Variety of objects (shells, coins, straws, sticks, gravel, etc.), either from the beach
or classroom, to represent buildings, seawalls, jetties, groins, etc.
 Optional - map of SC coast- NOAA nautical charts and/or topographic maps work
well
 Optional – directional compass
For Beach
 No materials are necessary for modeling on the beach since there is an unlimited
amount of sand! Objects found on the beach such as shells and dried grass stalks
can be used to represent buildings, groins, and seawalls.
 Optional – map of SC coast – NOAA nautical charts and/or topographic maps
work well
 Optional – directional compass
Procedure
1. Divide the students into teams (Map Team A, Map Team B, Longshore
Current Team, Seasonal Change Team, Hurricane/Storm Team, Development
Team, Coastal Engineering Team A, and Coastal Engineering Team B). Each
team will be responsible for one aspect of the modeling. Depending on the
number of students, team size may vary and teams can be expanded or
combined.
2. Gather students around the work area (wave table or swimming pool). Sand
should be smooth and flat to begin with.
3. On the beach, students can form an oval. Ultimately, they will need to kneel
in the sand. As they model, especially on the beach, hands will get sandy. It
----------------------------------------------------------------------------------------------------------------------------- --From COASTeam Aquatic Workshops: Oceans (grade 5); a joint effort between the COASTeam Program
at the College of Charleston and the South Carolina Aquarium – funded by the SC Sea Grant Consortium.
3
is extremely important on the beach that students do not stand up and
brush off sand so that it blows into someone’s eyes!
4. Map Team A - Ask students on the Map Team to “draw” the aerial view of
the outline of a barrier island in the sand. Maps may be used as a reference
and are helpful to get a preliminary outline. Students should decide which
direction represents north, east, etc. (a compass may be used to determine true
orientation) in relation to their barrier island. For Atlantic Coast beaches, the
long axis of the island generally runs north and south. See Appendix A.
5. Map Team B – Students on this team should next add appropriate topography
to the model. They can draw on their own experiences: is a SC beach
mountainous or flat? (flat) Where do you see “bumps” on barrier island?
(dunes) Is there a steep drop-off at the water’s edge or can you wade into the
water for some distance? (shallow slope) Or examine a topographic map to
determine actual elevation. Note: for this model, the vertical scale will be
somewhat exaggerated in order to see various features. The resulting basic
barrier island model should look like an elongate oval mound. The classic
“drumstick” barrier island shape can also be incorporated. Additional features
include dunes, ridges and runnels, and sand bars. Students should mark the
water line on the model. A good portion of the active beach is actually
underwater!
6. Longshore Current Team – The next step is to model some common coastal
processes. The longshore current is a wave-generated current that transports
many tons of sand along the beach. It exists in the surf zone or area of
breaking waves. Ask students if they have ever played in the waves at the
beach and suddenly noticed that they had drifted from their starting point. Of
course, if the longshore current transports them, certainly the sand is
transported as well.
Since the longshore current is wave generated, the angle of the approaching
waves determines the directions of the longshore current on the beach
(Appendix A). Typically waves seen breaking on East Coast beaches are
created by wind blowing across the water’s surface far out at sea. The
predominant wind direction drives the wave direction, which in turn
determines the longshore current direction. The prevailing winds in the
Atlantic are northeasterly so waves tend to approach the beaches from the
northeast. In general, the dominant trend on SC beaches is a north to south
flowing longshore current. It should be noted that one could observe a south
to north longshore current when the wind direction does change.
7. Students (on longshore current team) can line up along the side of the island
determined to be the east or ocean side. Beginning with the northernmost
student, she or he should push a handful of sand up the slope of the model at
an angle and drag it straight back down the slope (as seen in Appendix A).
The next student in line should take the “sand packet” and repeat the motion,
passing the sand to the next student. Meanwhile, the first student should
continue to move the sand so that sand is moved continually. The last student
----------------------------------------------------------------------------------------------------------------------------- --From COASTeam Aquatic Workshops: Oceans (grade 5); a joint effort between the COASTeam Program
at the College of Charleston and the South Carolina Aquarium – funded by the SC Sea Grant Consortium.
4
in line at the south end of the island will receive the sand and push is around
the tip of the island to form the sand spit. After a few passes of sand, pause
the activity and allow students to examine the results. Some obvious changes
might include sand loss at the north end of the model and sand gain at the
south end. This is in fact a common trend on East Coast barrier islands.
8. Seasonal Change Team – This team models the high-energy (larger) winter
waves and the low-energy (smaller) summer waves (Appendix B). The team
should line up along the ocean side of the model. All together, students
should take their hands and reach up the beach face and scoop away some
sand, pulling it toward the ocean side. Repeat this several times until a second
ridge of sand is built parallel to the island model. This smaller ridge
represents an offshore sandbar. The removal of sand from the beach face may
have carved a scarp or ledge into the beach or even the dune. This often
occurs during winter Nor’easter storms. The beach has narrowed and aside
from the scarp the slope has become flatter. The next step is to model the
summer waves. To do this the students should push the sand from the sandbar
back to the beach. They can continue until the entire bar is wielded back onto
the beach. This new profile represents the summer beach. In most cases a
sandbar remains off the beach but is decreased in size during the summer
months.
9. Hurricane/Storm Team – Another major influence on the geomorphology of
barrier islands is the occasional large storm or hurricane. The Storm Team
can take position along both the east and west sides of the model. Since a
storm surge or bulge of high water usually accompanies hurricanes, barrier
islands are often breached or washed over. When a storm surge does wash
over an island it can carry an immense amount of sand and deposit it in the
maritime forest, salt marsh, or beyond. As the water from the storm surge
retreats, it can cut deep gouges through the island to the extent that new inlets
may be formed. Students can model this process by pushing sand from the
ocean side of the model to the students across from them. Those on the inland
side can continue the process and pull the sand across the model to “deposit”
it on the west side. New inlets or breaches in the island can also be created in
this major rearrangement of the topography of the model.
10. Development Team – This team can use the objects to create a developed
barrier island. Ask students to predict and then demonstrate what could
happen to buildings at the erosional, north end of the island or what could
occur during a storm surge.
11. Coastal Engineering Team A – Use straws, sticks, pencils, or piles of gravel
to represent groins, shore-perpendicular structures used to trap sand. With
groins in place, ask students to predict what will happen to the sand
transported by the longshore current. (Appendix C: the sand is deposited on
the updrift side of the groin and carved away from the downdrift side).
Although groins strap sand, the current continues to flow and picks up sand on
the downdrift side of the groin. Groins can even impact other beaches o the
south and lead to additional problems for downdrift beach communities.
----------------------------------------------------------------------------------------------------------------------------- --From COASTeam Aquatic Workshops: Oceans (grade 5); a joint effort between the COASTeam Program
at the College of Charleston and the South Carolina Aquarium – funded by the SC Sea Grant Consortium.
5
Many geologists and coastal zone managers believe that groins are more
detrimental to the beach system than they are helpful.
12. Coastal Engineering Team B – This team can simulate change associated
with a seawall or revetment. These structures are built parallel to the beach
and are intended to protect development on the landward side of the structure.
Use pencils, sticks, or straws to build a seawall or gravel to build a revetment.
Sand may be piled up on the west side of the seawall and houses added if
desired. Waves often carve away the sand at the base of the seawall. Students
can model this by pulling sand away. Eventually when enough sand is
removed, the wall becomes unstable.
Assessment
Have the students draw a diagram of the barrier island that they just created in the sand
and also of the beach profile. Tell them to label all wave action, current directions, beach
structures, and man made structures that relate to the island. Diagrams should be very
similar to Appendix A, B, and C.
Rubric (out of 12 points):
Label longshore current (2 points)
Label swash and backwash (1 point each)
Draw barrier island like drumstick model (2 points)
Label dune (1 point)
Label scarp (1 point)
Label berm (1 point)
Label ridge and runnel (1 point each)
Draw and label sand bar (1 point)
Draw groin with build up of sand on one side (1point)
Members of the COASTeam Aquatic Workshops development team include: Katrina Bryan,
Jennifer Jolly Clair, Stacia Fletcher, Kevin Kurtz, Carmelina Livingston, Leslie Sautter, and
Stephen Schabel.
----------------------------------------------------------------------------------------------------------------------------- --From COASTeam Aquatic Workshops: Oceans (grade 5); a joint effort between the COASTeam Program
at the College of Charleston and the South Carolina Aquarium – funded by the SC Sea Grant Consortium.
6
Appendix A
Appendix B
Appendix C