The mission of the Gulf Intracoastal Waterway is to connect from Carrabelle, FL to Brownsville, TX with a navigable inland channel for transportation and recreation. The entire system is around 1050 miles long. As part of the Gulf Intracoastal Waterway, they connected waterways from Mobile Bay to Pensacola Bay. In 1934, this project cost $443,000 and connected Big Lagoon, Old River, Perdido Bay, Bay La Lanche, Wolf Bay, Portage Creek, Bon Secour River, and Bon Secour Bay. Connecting these waterways included 2 land cuts of about 7 miles in length. The canal was supposed to be 9 feet by 100 feet channel. Many commodities travel along this route including grain, coal, sand, gravel, lumber, gasoline, steel, and iron. In 1979, 7.9 million tons annually travelled from Pensacola Bay to Mobile Bay. The place you will visit for this Earthcache will take you to an original part of Portage Creek. However, this area has been turned into much more than a "CREEK". There are many debates on whether it is worth the environmental impact created from this project. They widened and deepened the creek to make room for a bridge and transportation of barges.
With any creek or river, erosion can greatly change the plans of humans. Erosion is the process in which the earth is worn away. The greatest of these eroding forces is water. With erosion of the banks, this distance has changed over the years. There are four basic types of erosion: hydraulic, abrasion, attrition, and corrosion. Hydroaulic is where wave action causes water to compress air into holes or cracks in the bank causing the bank to eventually collaspe. Abrasion is where sediment being carried in the water causes deep scraps along the base of the stream. Attrition is when rocks collide producing smaller, smoother rocks. Corrosion happens when carbon dioxide in the water forms a weak acid that eats away at soft rocks such as limestone and chalk.
When you visit this area, you will observe a variety of ways to try to tame the water. Some work better than others. Riprap, railroad ties, and concrete may appear to solve the problem of erosion, but how well do they really work? Near riprap, which are loose stones meant to protect the bank, water flows quickly and deflects off the stones which allows it to gain velocity. This means that unprotected banks have increased erosion. One of the largest environmental effects of the increased transportation along this route is the disappearance of seagrasses. Seagrass beds provide a stable root system as well as food and protection for many commercially valuable young fish and shellfish. They also help to disperse wave action and filter runoff. When boaters travel or anchor in shallow areas, deep scars in seagrass beds are created. Lost of seagrass beds can also effect how much erosion takes place.
Please send answer to the following question in an email and do not post them in your log. You will not keep a smiley if an email is not received.
1. Standing at the GZ location facing north, what type of earth do you find here?
2. Go to the first reference point, is the same type of earth here as the first location?
3. From the same location, what types of seawalls do you see from here? Have they been effective in stopping erosion? What proof do you see? What type of erosion is shown here?
4. Go to the second reference point and read the information signs. Do you see any seagrasses around this area? According to the sign, what are the three ways can you help seagrasses which would slow down the erosion process?
If you choose to, send a photo of traffic on the canal or wildlife you observe in these location.
References:
http://web.archive.org/web/20051208070639/http://www.usace.army.mil/inet/usace-docs/misc/nws83-9/entire.pdf
http://en.m.wikipedia.org/wiki/Gulf_Intracoastal_Waterway
http://gulfsci.usgs.gov/gom_ims/pdf/pubs_gom.pdf
http://www.alevelgeography.com/?page_id=162