Student Activities

Castles on the Sand

Overall Rating

Add your review
Grade Level:
Upper Elementary: Third Grade through Fifth Grade


Students will construct sand castles while utilizing engineering materials to stabilize and protect their "investment." Small groups of students will work together to select the location, construct and develop the castle, lay out and fabricate the defenses and discuss their design with the rest of the class during the "Castle Tour." Students will observe the impact of the rising sea level (the incoming tide) on their development and engineering features.


Assateague Island National Seashore was established with the goal of balancing human use and recreation with the preservation of natural resources. As a barrier island adjacent to densely populated resort communities, Assateague is affected by of a wide range of natural and human forces. The weather, biota, and human visitors of the island all exert their influences on the physical and biological character of this unique and dynamic park. Barrier-island development is a risky business. Assateague Island is one of the few remaining natural barrier islands in the mid-Atlantic where the dynamic nature of the island is unencumbered by human development. Ocean City, Maryland, located north of Assateague Island, is an example of a heavily developed barrier island. Millions of people visit Ocean City each year and billions of dollars have been spent on city development since the 1930's. Barrier islands serve important functions such as protecting the coasts, sustaining unique ecosystems and providing habitat for a diversity of wildlife. The allure of waterfront properties and vacationing at the shore is strong and Ocean City is a valuable part of the regional economy. A balance is needed between conservation and further development.


Students will be able to:
1) Work as a team to design and construct a sand castle
2) Incorporate engineering measure to stabilize and protect their castle (groins, jetties, dunes, bulkheads)
3) Describe the natural movement of barrier islands
4) Recognize the risk and expense of maintaining their castles
5) List cause and effects of regional and global sea-level rise.


This activity needs to be aligned with an incoming tide. Tide charts for Assateague Island can be downloaded from

Step 1) Explain the background of the activity. Small teams of students will build a sand castle and fortify against the waves using a variety of materials. The team that builds the longest standing castle wins. Students are awarded points from the judges (teachers) for design, artful layout and imagination. Students are also expected to give a tour of their castle and explain to the class their design concepts , their use of materials and any special features.

Students can purchase materials to use to protect their castles. Before they begin the activity, have them collect ten sea shells they can use to buy the materials with. These "sand dollars" will be used as exchange for raw material such as sand bags, short lengths of plastic landscape edging, pieces of lumber and other odds and ends. Teachers can assign different values for the different materials: 5 "clams" for a piece of wood, 10 for a piece of edging, 20 for a sand bag.
Please practice "leave no trace" and bring home everything that went out. Plastic and wood will float away. Students need to keep a close eye on their castle and ensure they grab the debris once the waves dismantle their development.

Step 2) During an incoming tide, have students observe where the swash zone is and make inferences as to where it will be in 20 minutes. This can be challenging and depends on the size of the waves and the slope of the beach. Finding the high tide mark or "wrack line" may help in choosing the proper location. Once a "20 minute" distance is selected, have students space out and select their build sites. To be fair, all construction sites need to be on the same line. Some of the students may notice the crests and troughs on the wet beach and the wise ones will select to build on the higher ground.

Step 3) Give the group 20 minutes to build their castles and to incorporate their materials. Keeping an eye on the encroaching waves, give the students incremental warnings of 10 minutes, 5 minutes and 1 minute. Time may need to be adjusted depending on the speed of encroachment.

Step 4) Once the construction is complete, begin a tour of each castle. Encourage the groups to explain their ideas and how they expect their protective engineering will work. Complement often on the artful designs and concepts. The tours may need to go quickly depending on the encroaching waves.

If time allows, ask the students if they have been to Ocean City, MD. Many will be very familiar with the resort town. Ask how the property owners along the boardwalk have protected their "castles". Discuss the expense of such protection and the necessary long term investment for beach replenishment due to the hardening of the beach front.

Step 5) Once the waves reach the castles, the students should observe how the water behaves around their fortifications. Have them take mental notes. Did they work as intended? How could they improve their design. Once the waves have impacted the castles, recognize the team that made the most durable castle and discuss why.

Step 6) The take home message: Barrier island are dynamic and constantly moving. Building a home or city on one is a risky and expensive endeavor. Today, the threat of rising sea-level make it even more ill advised.

Park Connections

In the 1950's, Assateague Island was slated to become another Ocean City. Visions of seaside vacation retreats and expectations of speculative profits from resale led some 3,200 parties to acquire 5,850 lots at Ocean Beach by the early 1960s, although fewer than 30 dwellings were constructed. Just as prospects looked brightest for the island's landowners, a storm on March 6, 1962, devastated Assateague. The protective dunes were severed in many places, and high winds and water destroyed all but the sturdiest structures. Only about 16 cottages, 17 gun clubs, and a few other buildings remained in the Maryland portion, many of them older structures on the relatively sheltered bay side outside the Ocean Beach subdivision. The road down the island was variously washed out and buried. The suitability of the shifting barrier island for private development, always a matter of doubt, was called much more widely into question.




Other data files can be downloaded from:

Download Sample tide chart: Assateague Beach, Tom's Cove

Last updated: October 5, 2015