Welcome to Watch Hill Beach!
Located in historic Westerly, Rhode Island, this beach is one of the most gorgeous beaches in the Ocean State! It's also the focus of this EarthCache.
What is Longshore Drift?
Longshore drift is the movement of sediment along the coast driven by wave action. It occurs when waves hit the shoreline at an angle. The swash—the forward motion of water as waves break—carries material up and along the beach at an angle. Gravity pulls the backwash directly downslope, returning water and sediment at a right angle to the shore. Over time, this zig-zag motion moves sand and other materials laterally along the beach, linking the processes of erosion (where sediment is removed) and deposition (where it’s laid down elsewhere).
What impacts Longshore Drift?
Wave Height
Wave height is the vertical distance between a wave’s crest (top) and trough (bottom). When high-energy waves crash steeply onto the beach, they increase the strength of the longshore current. This stronger current can carry more material down the shore. Conversely, smaller waves that break gently tend to produce slower currents and move less sediment. Even subtle differences in wave energy can significantly impact the extent and rate of longshore drift.
Wave Size and Energy
Large bodies of water, such as oceans and seas, have the space to generate more powerful wave systems. These waves carry more energy and can move larger volumes of sediment along the coast. The result is more aggressive longshore drift. Smaller lakes or sheltered bays typically produce gentler, lower-energy waves that transport much less material.
Fetch
Fetch is the uninterrupted distance over which wind blows across open water. A longer fetch gives wind more time and space to generate large waves. Oceans have enormous fetches, which allows for strong, sustained wave energy that powers coastal processes like longshore drift. In contrast, small lakes have shorter fetches, limiting wave development and reducing the potential for significant sediment transport.
Accessing this EarthCache
Depending on the time of your visit, parking may be limited. I've provided the city-owned parking lot I used as a waypoint on this cache page. It was free for the first half hour, but paid after that. There is also free street parking around the block in Watch Hill that you can also use. Please note that there are no dropoffs at the marked beach trailhead. While you might be tempted to pace the rocks and stare out at the midnight sea, please visit this EarthCache in daylight hours.
LOGGING REQUIREMENTS
Please submit your answers within seven days of your online log.
0) What is the name and GC code of the EarthCache you are visiting? Longshore Drift at Watch Hill - GCB00CD
1a) What are the wave conditions like at the time of your visit? (Are there large waves or small waves?) Feel free to provide a rough estimate of the height of the waves.
1b) Based on the wave height, do you think there is a lot of sediment being deposited onto the beach at the time of your visit?
2) Do you see any sediment being deposited onto the beach? If so, what direction is it being deposited (east or west)?
3) Comparing Watch Hill to a smaller lakeshore (for example, Lake Erie), where would you expect to find more sediment being deposited? What conditions of Watch Hill led you to this conclusion?
4) Take a photo of you along the shore of Watch Hill. If you're camera shy, you can also write your caching name in the sand!