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On August 29 of 2012, Hurricane Isaac made landfall in southern Louisiana. Although only a category 1 hurricane, Isaac still caused an estimated $2.35 billion worth of damage along with a death toll of five people in the United States. Hurricanes have long been a part of the disturbance regime in the northern Gulf of Mexico, but major efforts have recently been put in place to try and mitigate hurricane damage, especially in the post-Hurricane Katrina era.

Summary
A category 1 hurricane, like Isaac, has sustained winds of at least 74mph and no more than 95mph. However, with increasing development in coastal areas, the more deadly effect from hurricanes has been storm surge. Storm surge is the rise in water level caused by the winds essentially pushing the water, and depending on the area, it does not take very strong winds to create a potentially dangerous storm surge. Isaac made landfall near the mouth of the Mississippi river with sustained winds of 70kt (81mph). This managed to cause flooding in large areas of southern Louisiana especially in St. Bernard, Orleans, Plaquemines, and St. Tammany parishes where water height was as much as 10 to 12 feet above sea level (water depth was sometimes even higher as portions of southern Louisiana sit below sea-level).

Besides for effects on populated areas, Isaac also had a dramatic effect on the wetlands and barrier islands of southern Louisiana which provide large amounts of biodiversity and offer numerous advantages to humans. The United States Geological Survey conducted multiple aerial surveys of landmasses specifically vulnerable to hurricanes. These surveys were done before and after Hurricane Isaac in order to provide a comparison. Photos of the Chandeleur Islands, a series of barrier islands off of the eastern coast of southern Louisiana, show significant erosion caused by wind and storm surge. Additionally, almost all of the pre-storm vegetation was lost.

Wetlands
A common problem associated with wetlands and barrier islands is that once they have been eroded and reclaimed by the Gulf of Mexico, they are likely to permanently remain open water. Wetlands and barrier islands originally formed from sediment deposition from the southern Mississippi River system beginning approximately 5,000 years ago. The river would carry sediment down its path, and seasonal flooding of the river would allow sediment to be deposited in adjacent areas. Additionally, forming distributaries would let the Mississippi River branch off, reaching new areas, and thus form large amounts of wetlands. However, humans have modified the natural paths of rivers. This process, known as channelization, has serious consequences for wetland ecosystems which include drainage of wetlands, degradation of natural habitats, and elimination of natural flow patterns. With levees, canals, and set channels for water to flow through, the river no longer floods and reroutes naturally and seasonally. The river is not able to deposit sediment in diverse areas to help create wetlands. Instead, the river flows through its artificially determined path and deposits the valuable sediment off the edge of the continental shelf. This lack of natural wetland restoration combined with the continued erosion from hurricanes causes a rapid loss in wetland area. Before human channelization of waterways, the river’s natural process of sediment deposition was enough to sustain the wetland habitat, but currently wetland area is on a downward trend. Since 1932, the Mississippi River Delta Basin has lost 70 percent of its land area. At this rate, it is predicted that less than 5 percent of the original land area from 1932 will exist in 2064. Additionally, levees and waterway barriers can trap storm surge and prevent proper draining. This often times will cause long periods of severe flooding that has its own consequences for wetlands. For example, after Hurricane Rita in 2005, the enclosed marshes of Chenier plain were flooded for over nine months following the storm. The problem that arises is that trapped storm surge has a very high salinity that kills native marsh. Research done by Gregory D. Steyer in the months following Hurricane Rita (later published in 2010) revealed that the Chenier plain that remained flooded had little vegetation recovery because of trapped saline water. However, in the eastern delta plain where the primary form of damage was wind and storm surge with little flooding, the vegetation recovered much quicker.

Recent Levee Systems
The Hurricane and Storm Damage Risk Reduction System(HSDRRS) was implemented by the Army Corps of Engineers after the devastation from Hurricane Katrina in 2005. The HSDRRS is a project aimed at completely re-engineering the levee system in New Orleans and surrounding areas in order to withstand effects from a “100 year storm,” or a storm that has a one percent chance of occurring each year. The project includes construction of multiple floodgates around the city, redesigning pumping stations to pump water out of the city, and raising levees while constructing seawalls on top of them. The system’s first real test came with the impact of Hurricane Isaac in late August of 2012. Although Isaac was only a category 1 storm, the speed of Isaac’s movement was considerably slower than most hurricanes, allowing more time for storm surge and damage to compile. Isaac produced tropical storm force winds for up to 45 hours while the effects of storms like Katrina and Rita only lasted for 21 and 16 hours, respectively. This suggests that even though Isaac was of lower intensity, the severity may have rivaled Katrina and Rita in certain locations. An analysis conducted by the US Army Corps of Engineers stated that the post-Katrina HSDRRS prevented potential flooding in areas within the strengthened levee, but potentially caused up to one foot of additional flooding in areas immediately outside of the HSDDRS.