To get to this cache, please do not park along the busy road here. See the parking coordinates in the additional waypoint section. There is a sidewalk where you can view the river and answer all the questions.
The Los Angeles is one of the largest river systems in Southern California. Many movies were filmed along the river, in downtown Los Angeles. Its watershed covers 826 square miles and all the water that enters it flows to this spot where it meets the Pacific Ocean.The closer the water gets to the ocean, the slower is flows which allows finer particles such as silt and sand to be deposited near the mouth of rivers, like the Los Angeles.
The Los Angeles River begins its 47.9 mile journey in the Santa Monica National Recreation Area, just north of Malibu near Calabasas. Other smaller creeks and tributaries also flow into the Los Angeles River, making it larger. These creeks include Tujunga Wash and Iron Hondo which go deep into the San Bernardino Mountains. These mountains have similar geology, both with strike-strip motion. The rivers in these mountains carry dissolved chemicals and sediments to which are carried all the way to the ocean at this point.
There are a few things to note when talking about sediment deposition from rivers. One thing, is that it depends on a few factors. Speed of the river (which varies quite a lot), size of the particle, and the calmness of the ocean. Let's discuss the speed of the river. The fastest part of the river is located in the middle, just below the surface. A common misconception is that middle of the river at its surface is the fastest, but due to wind this slows it down. The edges and shorelines of the river are always the slowest.
Rivers can deposit different sediment. Sand, silt, and clay are the most common, but during large rain storms and floods, rivers can move large rocks and even boulders. Silt is the smallest particle that rivers can carry. See the chart below for the particle and their given sizes. A thing to keep in mind is that the smaller the particle is, the calmer the water needs in order for it to be deposited. It's one of the reasons why sand makes up beaches, and not silt or clay. Silt and clay are suspended in the ocean waves until they are carried enough out to see where the water is calmer, and are deposited on the ocean floor.
During storm seasons (November - March), the river can flow quite fast near the mouth, making deposition difficult and only occurring offshore. Because the mouth is located in downtown Long Beach, much of the river is made of concrete basins rather than a natural river valley like Newport Back Bay. A concrete basin allows water to flow more quickly, to reduce flooding upstream. It also allows easier control methods to reduce pollution as it is much easier to see where the point source is coming. However, during flooding, natural rivers push larger sediments, such as boulders, to the sides creating natural levees and protecting the river for years to come. Most of the time, the river doesn't flood and brush begins to grow on these levees, soaking up water during rainy seasons. Plants protect the rivers in addition to the natural levees. With the Los Angeles River being a natural river, but altered with concrete basins, flooding will occur more frequently especially in low lying areas near its terminus.
Works Cited
https://geomaps.wr.usgs.gov/parks/rxmin/sediment.html
https://en.wikipedia.org/wiki/Los_Angeles_River
http://www.geography.learnontheinternet.co.uk/topics/river_deposition.html
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. "Los Angeles River Terminus" on the first line of your email AND list all geocaching names of your party so I can match your answers to them. If you all want to learn something, I would prefer each cacher send me individual emails in the spirt of earthcaching. However, this is not required.
2. As you walk to the above coordinates, look for any signs of levees along the banks of the river. If they exist, tell me: are they natural or man made? And how can you tell?
3. Look at the river towards the Pacific Ocean. Describe the conditions of the water. How fast is it moving? Is it choppy or calm? What direction is it moving? Etcetera.
4. Describe the water clarity and quality. Can you see any sediments? If so, according to the sediment chart, what can you see? What are the sizes or shapes? Explain.
5. As you walk back to your car, look for signs where the city has prepared itself in case of a massive flood. Do you see anything that would help prevent a flood (or tsunami) in a major storm?
