This Earth Cache brings you to Kill Devil Hills on the Outer Banks of North Carolina.
Your mission is to observe and report several indicators that this beach is on the move. Here you will find an excellent opportunity to observe the geological process known as overwash. You will also note the role that wind, vegetation and humans play in the geologic status of this beach.
Overwash: The term overwash refers to the transport of sediment landward from an active beach by coastal flooding during a tsunami, hurricane, or other event with extreme waves. During storms, large volumes of sediment are eroded from the seaward side of the island and re-deposited toward the sound side in large overwash fans. An Overwash Fan refers to the distribution of sediment in a “fan” pattern after the ocean water has breached the dune line. Fans often clear a vegetation-free path from the ocean to the inner water body: in this case Kitty Hawk Bay on the Albemarle Sound. Overwash fans will be most apparent at this site after hurricanes and will occur in the weakest area of the dune line.
Wind: Wind is also a factor in the movement of sand away from the beaches. Wind moves sediment primarily from the east and north east toward the west and south west. Wind moves sediment on the beach surface as well as through wave energy. The town of Kill Devil Hills practices beach renourishment and wind erosion control in several ways.
Erosion control fences are in place in some, but not all, areas. Driftwood or other natural materials are also used as erosion control fences.
Vegetation: Naturally occurring vegetation on the dunes at Kill Devil Hills plays a crucial role in protecting the island from storm overwash and wind erosion. Plants species such as Spartina Patens, Sea Oats and American Beach Grass are able to recover quickly from storm erosion and thus stabilize the dune.
Humans: Heavy recreational use has threatened the stability of the dunes. Humans often cause irreparable damage to dune vegetation by walking in non-designated areas. Frequent recreational vehicle traffic reworks the profile of the beach leaving the dunes exposed to greater wave energy.
STAY OFF THE DUNES -- Ground Zero was marked with a GPS in the easement between the dunes.
To claim this Earth Cache please answer the following by email: Do NOT post on your log.
1- You will survey the encroaching tide for evidence that overwash has occurred or is probable. Visit the posted coordinates at HIGH tide and make your way to the water line. Send us the coordinates you capture while standing in this spot. Measure and report the distance from ground zero. Also note if you are east or west of GZ.
2-The town of Kill Devil Hills has placed wind erosion control fences in some areas, but not all. At Ground Zero did you observe any effort being made to address wind erosion? Describe what you saw.
3- Dune vegetation is important to sediment retention. Based on your observations and using the above information as a guideline, describe the dune vegetation near Ground Zero. Also indicate if vegetation is dense, sparse or non-existent.
4- Based on your observations and using the above information as a guideline, did you notice any evidence of human activity that may hasten the movement of the shoreline?
5- OPTIONAL—post a photo of you and/or your group. You may also post photos relevant to the questions above.