Levee Design Essay

Flooding of the settlement was problematic. By 1812, the settlers had built miles of levees on the banks of the river. For the next two hundred years, the surrounding wetlands were drained to eliminate swamps filled with yellow fever carrying mosquitoes and to encourage economic development. Draining water from peaty soils encouraged subsidence. The land which was just inches above sea level to begin with steadily sank. In combat of this, higher and stronger levees were built, tightening the straight jacket already placed upon the Mississippi River. The massive flooding of 1928 brought further flood control systems implemented by the Army Corps of Engineers with Congressional blessing. By the 1950’s, dramatic rates of land loss in Louisiana’s coastal zone stretched across 300 miles from Texas to Mississippi and inland 50 miles. (Tibbetts)

3.5 million miles of water run throughout the United States; and since the country’s conception, over 80,000 dams have impounded 600,000 miles of these waters [1]. Dams were originally constructed to provide water to towns and establishes energy sources for mills and later hydroelectric plants. Because these dams were constructed decades ago, they’re reaching a critical point of obsoleteness where they cause more harm than good. Dam removal is increasingly popular across the country to address the ecological problems including habitat loss and sedimentation, despite potential for downstream harm, removing dams is more environmentally and economically cost effective than upgrading them. The Marmot, Glines Canyon, and Elwha river dam removal projects each highlight different challenges of dam removal, but overall

1. The reasons why some buildings are in the floodplains is because of agricultural industry. Another reason is population growth and expansion into those areas where people felt safe because of improvements of levees. Even though people were told about the dangers most people relied on disaster insurance instead of flood insurance. There should be laws that prohibit further development of these areas because it is costing the taxpayers lots of money for people that want to live in these areas that know the risks. If there were laws in place they could use some of the land as soccer fields and football fields as overflow ponds if they do want to build in a floodplain they need to raise the ground up by hauling in soils that will let the water pass through into those overfill ponds.

Levees are very helpful in a lot of ways and are needed to have a safe place to live, but they hurt the marshes that surround Louisiana. The levees that surround the Mississippi River are very good at their job and keep the river contained but with the river contained, there is no natural flooding that occurs in the coastal marshes and without the natural flooding, there is no depositing of sediment that replenishes and builds up the marsh. This creates an upset in the balance of land loss and land gained. The subsidence due to the lack of new sediment accounts for 53% of the land loss in Louisiana over the past

Instead of sustaining marshes, it adds on to the problem. From page 36, it states, “They direct river water straight into the Gulf of Mexico, where it no longer deposits sediment along the coast.” Levees have the capability to stop the sediment, and that’s a huge detriment to the marshes. Therefore, levees can’t support the marshes that well and keep the sea level rise.

Katrina hit New Orleans, Louisiana on August 29th, 2005, but the failure of the government started before this day “by allowing building and growing in areas in low flood lands.” The government did not regulate these land areas that have always been at a threat for flooding and natural disaster, which was ignored by the government and public, and was in place, still a place for growing infrastructure. Failures included by the author of the national agencies include design limits that can lead to levees being overtopped by flood and hurricane events that are larger than they were designed for and design flaws and construction and maintenance shortcomings that lead to protective works being breached when they cannot stand up to the forces exerted by large flood and hurricane events. The author also points out the problems with the hundred-year flood event, which only has a one percent chance of happening every year. When the NFIP focuses on this possible catastrophe, it losses the

The Ellicott City flood was destructive because it was on a high gradient stream. The high gradient stream made it flood faster, and had low stream discharge. Discharge is cross section of stream channel. It was also capable of moving large particles, which is an example of deposition and erosion. In the experiment, the ‘Main Street Ellicott City’ stream was more affected than the Meandering Stream. The Main Street Ellicott City stream was flooded faster, and more houses and cars were destroyed compared to the Meandering

Many communities are suffering due to coastal erosion. One example is the village of Cocodrie, LA in Terrebonne Parish. This village’s small population and its 220 residential and commercial buildings are surrounded by marshes. In Cocodrie, there is no barrier against hurricanes. Local marinas play host to recreational and commercial fishing, and The Louisiana Universities Marine Consortium is located in Cocodrie. This facility of around 100,000 square ft houses laboratories, classrooms, and a research center. Infrastructure that will be affected by coastal erosion includes paved highway, dirt roads, a bridge, water supply systems, and natural gas lines. By 2050, Cocodrie will be surrounded by open water as the marshlands around the village give way to rising sea levels. Another community affected by this issue is Yscloskey, LA in St. Bernard Parish. The most important part of the economy here is fishing, and highways link the parish to New Orleans fishing communities. The Yscloskey area lies outside of the protective levees and is quite vulnerable to storms. Though losses in Yscloskey are not predicted to be as great as those in Cocodrie, a 16 percent loss by 2050 leaves the infrastructure of Yscloskey even more vulnerable (Coast 2050, 1998, p. 64-66). Local residents in these areas are watching the land disappear along with the beachfronts and Cyprus swamps that were on that land (Marshall, 2014).

The levee system has disrupted the natural deposits that are left from the overflow of the river.2

The 17th street Levee, located along the Lower Ninth Ward was breached, causing most of the flooding in New Orleans. National Public Radio reported that many investigators are finding that the breaches of the London Avenue Canal and the 17th Street Canal were caused by severe engineering flaws. The same walls both failed when the water rose only about half way up the wall, proving that the levees were poorly constructed in the Ninth Ward (npr.org). Bob Bea is an engineer and professor at the University of California, Berkeley, and was given the task by the National Science Foundation to find the cause of the breaching of the levees. According the Bea, the levees had a weak enough layer underground to allow the levees to break. The Army Corps, who are responsible for building the hurricane-protection system of New Orleans, require that floodwalls be created 30% stronger than what the minimum amount requires to hold back water. By the Army Corps guidelines, they are also required that the underlying soil is weaker than what tests show, usually in the bottom third of the original measurement (npr.org). The culprit to the breaching of the wall was a weak layer of clay that had no possibility of holding back Katrina. How could the Army Corps engineers miss such an area? It is very reasonable that the overseeing of the

New Orleans was built on a marsh. The city was inundated by water during Hurricane Katrina in 2005, causing a tremendous loss of human lives and costing the economy billions of dollars in damage. Since the storm, the U.S. Army Corps of Engineers has built a system of lift stations and levees to control the flow of water around the city. This has created what is best described as a bathtub surrounded by water. To further elaborate, New Orleans is the bath tub, while Lake Pontchartrain and the Mississippi River surround the city. Over the years keeping water from entering the city has become more difficult because the city continues to sink lower below sea level. Subsidence of marshy soils lowers the ground elevation in and around the City of New Orleans. The gradual caving in or sinking of land is known as subsidence.

The seawall was constructed at Long Beach to prevent further coastal recession and to protect personal properties, community areas and infrastructure threatened by erosion along Long Beach. A seawall has been present at Long Beach for many years but the current seawall was officially opened in 2010. I 2010 when the seawall was updated a new promenade was also constructed to encourage the use of the area. The construction of both the seawall and the promenade totalled a cost of $5.6 million. By preventing further coastal recession, the properties and community areas situated along the coastline and at low elevations are protected from becoming inundated or damaged as a result of erosion. Seawalls in some cases have been known to disrupt the natural flow of sand along the beach and lead to increased erosion in front of the wall as well as at the end of the wall. Although this increase in erosion is a risk, the presence of this potential issue is not currently obvious at Long Beach. The seawall at long beach was constructed with a slope which dissipates the energy from the waves. By using this design there is less risk of further erosion as a result of the seawall and the seawall is hit with less force and is less likely to become damaged from the force of the waves in the near future. As well as the design of the seawall, the seawall is also strengthened using

The purpose of this report is to geologically evaluate the potential hazards for flooding in Hazard City. This report will include a detailed historic and extrapolated Stream Gauge Data Worksheet, as well as a graph of the Discharge Frequency Curve expected on Clearwater River. The report will provide Hazard city with my scientific analysis, conclusions, and provide recommendations concerning potential flood damages.

We will begin to use autocad software to gain a clear picture of the building and the surrounding area to help see possible sites where erosion might be a problem. The area in which the building will be located is subject to erosion from wind, rain, and water, which is the primary source of erosion in Alabama. Therefore, protection from water erosion caused by rains will be one of our primary concerns. The autocad software will tell us the area we need to protect in it entirely, and we will use a black silt fence for his purpose. Black silk fence comes in rolls of hundreds of feet, and if that isn’t enough connectors are available to connect additional silt fence.

As already mentioned, the architect has to understand the flow of the river, thus, there are restriction in building below the flood level of the river. Restrictions apply to building on the hillsides as well, as landslides could become a problem. Thus, the buildings should be reinforced, and would, therefore, cost a lot more.