The Jupiter Inlet was first shown on maps dating back to 1671, according to the U.S. Army Corps of Engineers, and has gone by many names over the years. It was the only outlet for the Loxahatchee River, Lake Worth Creek and Jupiter Sound with part of the flow from the St. Lucie and Indian Rivers diverting to the ocean through the Jupiter Inlet as well. The flow was sufficient to maintain adequate depth through the natural inlet with the exception of severe storms that closed it temporarily for short periods of time.
Prior to 1913, the inlet was apprximately 1,250 feet South of its present location. An 1855 map of the Fort Jupiter Reservation shows the inlet in this position with a more southeastern orientation of the inlet joining the Atlantic Ocean. After the 1892 construction of the St. Lucie Inlet by making an artificial cut through the barrier strip about 10km north of Jupiter, the altered hydrodynamics would in time facilitate the need for management of the Jupiter Inlet to reduce shoaling and maintain a navigable channel.
Longshore Current and Beach Drift
Waves in this area along the coast of Florida break at an angle to the shoreline, which is called a longshore current. The direction of the longshore current reflects the angle of the wave approach.
Beach drift is defined as the pulling of sand particles sideways along the beach. Sand grains are transported as the waves move onto the beach. Since the waves at this location hit the beach at an angle, the sand grains are being carried to shore in that same angle. When the water retreats back to the ocean because of gravity, the sand goes straight back perpendicular to the shoreline. Due to the fact that grains are redeposited as the water retreats, the grains are actually deposited further down the beach, otherwise known as down longshore current. Because of the movement of the sand grains, the net overall movement of sand is down current. Sediment that has moved downshore is replaced by sediment from further upshore, as long as the sediment is available.
The net movement of sediment in the figure 2 below is to the south because the waves are hitting the shore from the north. If the waves changed direction and hit the beach from the south, the net movement of sand will be to the north. Net beach sediment movement, or beach drift, can change back and forth due to the shifts in wave direction.
Jupiter Inlet District Sand Bypass Project
As with most inlets, the Jupiter Inlet has the tendency to get shallower due to the fact of sand moving past the channel and filling up the channel. To offset this problem in 1997, the Jupiter Inlet District's North and South jetties were raised and extended to improve navigational safety, improve sediment bypass, and reduce sedimentation into the estuary and blocking the channel. The project reduced the sand flow from the jetty walls but sand transport still erodes the area to the south of the wall.
The interruption of natural sand flowing south is estimated to cause sand losses on the beaches south of the inlet. To offset the losses and maintain a healthy shoreline, sand is occasionally dredged from sand trap located in the inlet. The sand is pumped through a submerged pipeline that is temporarily laid across the seafloor and placed below the harbor ship channel. A hydraulic suction dredge removes the sand from a 6.58 acres section sand trap located 1,000 feet west of the inlets mouth and moves it through the pipeline. The sand delivered through the pipeline is placed on the beaches south where it is then shaped. The sand bypass project is done in this area every few years as shoaling builds and the south jedi become smore erodded due to sand transport. The sand is moved in the spring as to not impact turtle nesting season.
To get credit for the cache, please answer the questions below. When answering the questions do your best. It is more important that you learn a new concept about our earth and can apply your knowledge, rather than have a precise answer.
1- Classify the tidal current at the time of your visit as “flood” (water flowing from the ocean into the estuary) or “ebb” (water flowing from the estuary into the ocean).
2- Which direction is the long shore current moving at the Jupiter Inlet Beach, seen south of the inlet and the coordinates?
3- From the cache page coordinates look at the beach shoreline at the North jetty. Now look at the beach shoreline at the South jetty. Comparing the two shorelines, if the south shoreline was at 0 feet how many feet does the north shoreline stick out into the ocean?
4- Comparing the shoreline north of the inlet to south of the inlet, do you think the shore has been restored lately?
5- Do you think the restoration project in this area has been effective? Give your reasoning.
Thank you for visiting this earthcache. Please send your answers to the above questions to the cache owner. In your "found it" log feel free to write about your experience, but don't include the earthcache answers. Thanks and we hope you enjoy beautiful Jupiter Inlet! Make sure you check out the Adventure Labs, and other caches located here and Dubois Park next door.