Barrier Island Dynamics
- 3 hours for field studies
- Group Size:
- Up to 24
- in the park
OverviewAssateague is a young, dynamic landform, changed constantly by wind and water. During this STEM program student teams use professional survey equipment to plot the topography of the beach, collect elevation data and graph their findings. Students collect wind and ocean current data and model island roll over. Students also assess and analyze engineering alternatives and beach replenishment projects for cost/benefit and sustainability.
1) Teach students to profile beach transects using professional equipment.
2) collect usable data for NPS beach movement records.
3) compile data on-line to show temporal changes to the island.
4) analyze pros and cons of various engineering alternatives used to counter beach erosion and sea level rise.
· describe the process of surveying a beach and constructing a beach profile.
· construct a beach profile and identify the parts of the beach (post-trip activity).
· describe the cause and evidence of tides.
· cite evidence of shore currents and sediment transport.
· describe the mechanisms of sediment transport and will cite evidence of where these mechanisms occur on the beach.
· identify coastal sedimentary features and describe their formation.
· describe human interference with natural coastal processes.
· describe coastal ecosystems.
· describe the geology, ecology, and physical oceanography of MD's seashore.
Assateague Island National Seashore is a barrier island that formed about 7,000 years ago along what is now the Atlantic coast of Maryland and Virginia. The island is constantly shaped and reshaped by dynamic coastal processes, including storm-driven overwash, dune formation, and sediment transport driven by waves and wind. These geologic processes, in combination with the island's underlying substratum, control a suite of delicate habitats.
As the barrier island migrates, landward, beach and dune sands are pushed westward onto the marsh and into the estuary. Inlets have opened and closed along the length of the island, reworking sediments and leaving deposits of coarse sand, gravel, and sandy flood and ebb tidal deltas. Periodic measurement of beach profiles can be a valuable asset to monitoring the erosion and depositional patterns of beaches.
Due to its dynamic nature, the island is one of the first areas to exhibit the impacts of climate-related changes, including sea-level rise, storm frequency and intensity, and changes in precipitation.
Method: Set up Topcon laser on primary dune roughly centered between the 5 elevation points. In the past, the laser has been set up approximately 20-30 m East of fence. In order to cover the rangeThe laser needs to be adjusted to strike the laser receiver in it's collapsed position
1) Introduce the group to the target area.
2) Record the elevation of the start points, this will be each groups starting point. (nail value.)
3) Deploy the self-leveling construction laser so that the laser strike the receiver below the 130 cm mark on the survey rod stationed at #1 start point.
4) Distribute compasses, flags, and meter tapes to the group.
5) Orient the group with the compasses. (profiles typically run along 111°.)
6) While two team members flags transects, remaining team members can work on collecting environmental conditions (wind speed, direction, wave frequency, angle of strike) using hand tools. They can also begin to excavate the 1m hole mid-point of the transect for sand bedding analysis.
7) From the starting points, facing 120° or its opposite, have each group lay down flags along the azimuth using the lensatic compass for guidance. (A straight line is crucial in order to obtain accuracy and precision). These points are near the group camping area. Numbers are meters above mean sea level:
1= 4.306 2= 3.984 3= 3.840 4= 3.946 5= 4.207
8) Once each profile line has been marked, distribute the survey rods with the attached laser receivers, and orient the group to its operations.
9) Starting with rods on top of the known elevation points and then working toward a desired end points (water's edge), record all measurements and distances from the starting points. Be sure to SECURE the end of the meter tape to the starting point. (NOTE: areas with radical feature changes require more measurements at shorter intervals in order to produce a useful profile.) (NOTE: For an area with extreme/abrupt height differences, a participant may have to hold the ends of the meter tape above the ground, clearing obstructions, to assure that it is taught.)
10) Once the desired data has been recorded, collect all materials and store them away.
11) Utilizing the data the group has recorded, the group could either map their findings by hand on graphing paper, or use Excel or a similar program to display their findings. Hands on the Land website http://www.handsontheland.org/environmental-monitoring/coastal-watershed-monitoring/beach-profile.html is hosting our beach profiling data and ideally the students should enter their data onto this site.
12) Over time, the raw data could be compiled and presented in a way that shows the island's dynamic sand movement. Even if the data is not accurate enough for scientific research, it could still be used to show participants island dynamics.
VocabularyShoreline: The line marking the intersection where land or shore and water meet. This ‘imaginary’ line moves up and down with the tides.
Beach: This includes the area from the coast or dune-line to below water level. The beach includes the shore and the shoreline.
Beach Face: The area of loose sediments from below the water line to the berm on a beach.
Berm: The area on a beach that is the highest point towards land that waves deposit or drop sand and other sediments. The berm is usually the highest point in height on a beach and often has a scarp or steep incline leading up to it.
Dunes: A hill of windblown sand that is stabilized by grasses and other plants. Dunes are not part of the shoreline but are the first part of the coastal zone. Dunes protect the land behind them from storm waves and strong winds.
Debris: Trash or garbage. Marine debris also includes shells, dead plants and animals, and driftwood. After high tide, a line of debris is left on the beach by the retreating tide.
Sea Level Rise: The increase in the height of the ocean due to a volume increase. This volume increase causes the sea surface or the level of the sea to rise. Sea level rise happens because of such natural occurrences as land subsiding (sinking) and land rebounding upwards as the weight of glaciers is removed (glacial rebound). Global warming caused by humans adding too much carbon dioxide to the atmosphere also causes the sea level to rise because of thermal expansion of seawater and the melting of land-based ice (glaciers and ice sheets).
Thermal expansion: The increased air temperature resulting from global warming will cause the temperature of the oceans and lakes to also increase. When water is heated, the spaces between its molecules will increase, causing an increase in volume. In the ocean, this increased volume will cause the sea level to rise.
Global warming: The increase in the temperature of the atmosphere and the oceans as a result of too much of the greenhouse gas, carbon dioxide, being added to the atmosphere. The greenhouse gases act like a blanket over the Earth to keep the sun's heat in. When too many greenhouse gases are added to the atmosphere, the effect is like adding a second blanket. This causes too much heat to be kept in the atmosphere and eventually some of the excess heat will cause the oceans to heat up as well.
Beach profile: A survey of the elevations of the surface of a beach to see how its elevations and features change over time. The end result of the survey is sideways profile from the water's edge to the dunes.