This earthcache will talk about the how the constant threat of erosion from oceanic waves damaging infrastructure here in Long Beach and the prevention tenchicues used to combat it. Long Beach Harbor has many businesses that bud right up against the ocean. As sea level rises and the ocean waves get more frequent and powerful, a set of measures were used to protect the land surrounding the harbor from costal erosion. Here, you'll see two of the most common technics. Usually, only one is in place but this site is special seeing both in action.
For starters, erosion from waves happen constantly. 24 hours a day, 7 days a week for millions of years. Long Beach is a costal town and like many others, is at constant risk of flooding due to the weather of the land. To help combat this, a series of seawalls were constructed here in the Harbor to help downtown Long Beach thrive without the threat of constant flooding. There is an unfortunate side effect to constructing seawalls too. They cut down on the biodiversity along the shore. Tide pools and marshes depend on the constant circulation of new, clean ocean water to supply organisms with dissolved nutrients and minerals. With out, life will perish and bacteria will thrive.
There are two types of seawalls implanted here that you'll see. One is a concrete wall and the other is a rock (boulder) wall or jetty. There are pros and cons to both of these. Pros for a concrete wall is that it's much easier to build and maintain as well as minimize the width of the wall. This helps by increasing retail space in the harbor, adding to the economy. On top of that, the aesthetics are much better. You may not even know it was there. Cons of the wall is that more time is needed to construct it than a boulder wall and it's prone to not last. It also cuts off links to organisms who depend on the ocean for survival. Those above the wall will likely die from dehydration and those below it will likely drown. Pros of the rock wall is that it's relatively easy to build and less planning is involved in it's construction. With the large boulders stack on top of each other, it leaves behinds large caves and cracks. This is good for animals to move through as well as waves aren't totally obstructed. Rather, they are slowed down as they reach further inland. It will also last much longer than a concrete wall. It's cons, however, include taking up a lot of usable space. The boulders are extremely difficult to transport and move once in place.
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 lost. 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.
Given enough time, 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. "Long Beach Harbor 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. Explain what you noticed and what you would have seen if it was high/low tide.
3. What direction are the waves coming from?
4. Do you think there is enough adequate erosion control techniques implemented here so that a sink hole doesn't appear in downtown Long Beach? 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. Using the diagram above, which option (A, B, or C) best shows what is happening at this site. Explain your reasoning.
7. Based on your own observations, which seawall (boulders or concrete) implemented here is more effective in protecting the infrastructure in downtown Long Beach? Which one is more effective in protecting the biodiversity? Are your answers the same or different? Explain.
Works Cited
https://caseagrant.ucsd.edu/project/explore-sandy-beach-ecosystems-of-southern-california/coastal-armoring
