Balboa Island is an artificial island in Newport Harbor. It was created by dumping sand and large rocks. Eventually, this accumulated to above sea level where it was leveled and planned for development. Ignored to insure the homes would last a long time, the entire island is surrounded by a 2 foot seawall. Depending on the tides, the water can come up to the sea wall or be about 15 feet away from it. Let's first take about the geologic importance of seawalls and how they are beneficial. Water is a natural erosion agent. Over a few days, it can move sand up and down a beach. Because Balboa Island was built with sand, this was an issue. A seawall would counter act the natural erosion of sediment from the island. It would prevent sea water from ever reaching the island and moving sediment.
Let's talk about the diagram above in more detail. Before the seawall is placed, the biodiversity is high. There is lots of life and many species are thriving. There is also a large beach with lots of area for species to move around.
When the seawall is initially placed, some biodiversity is losses. This is due to the fact that some smaller animals cannot go over the seawall. They are either trapped on the beachside of the wall, or are trapped on the water side of the wall. Birds and other animals that are large enough to go over the wall, are not effected. The beach is also steepened due to the fact that the beach is eroding faster closest to the ocean.
In a few decades, when the beach is completely eroded, the water will actually be at the seawall. This is when biodiversity is at its point for greatest loss. The beach is gone and will never come back and the same goes with most of the animals who lived there.
The seawall is a temporary fix. Given a few more decade, and the water will actually cut the sediment below the seawall and go under it. Eventually, it will create a sinkhole in the ground and will consume what ever is underneath. But, this will only happen if things are not regulated. If the sea wall is regulated, then sediment can be added every few years to the base of the sea wall to counter act the erosion. This will help prevent a sinkhole from forming, but will not always stop one from occurring. In the end, mother nature always wins no matter how hard we try. But in the short term, humans will try everything we can to combat erosion of our beaches and islands.
TO LOG A FIND ON THIS CACHE YOU MUST GIVE ME THE CORECT ANSWERS. YOU CAN CONTACT ME THROUGH MY EMAIL OR THE GEOCACHING MESSAGE CENTER. ANY INCORRECT ANSWERS WILL RESULT IN A DELETED LOG
1. "Balboa Island Seawall" on the first line of your email AND list all geocaching names of your party so I can match your answers to them. Note, this IS cheating as only the person who sent their answers has learned something, while the others get a "free ride". It's not fair to others. If you all want to learn something, I would prefer each cacher send me individual emails in the spirt of earthcaching.
2. Tell me the time you visited and see if this matches any high tides or low tides. If it does, explain what you noticed.
3. How far are the waves from the seawall?
4. Do you think there is enough adequate erosion control techniques implemented here so that a sink hole doesn't happen on the island? Explain.
5. If a large tsunami entered the harbor, how would the seawall effect it if at all? Explain what would you think would happen.
6. There is an Orange County Surveyors benchmark on the seawall that has "NB3-20-**" as it's designation. It's where the seawall meets stairs to the bridge. The last two digits "**" in the designation represents the year it was placed, as well as the year the seawall was finished. Based on this information, and your own observations, in the diagram above what picture (A, B, C) would closely match the site here? Explain the similarities to the site and the picture you have chosen as well as the differences from the others.
Works Cited
https://caseagrant.ucsd.edu/project/explore-sandy-beach-ecosystems-of-southern-california/coastal-armoring