US Army Corps of Engineers USACE

The US Army Corps of Engineers is responsible for the coastal protection. The

Corps is preparing an evaluation of the performance of the hurricane protection system (IPET, 2008) of the coastal zone of Louisiana, analysing the functioning of the system during Katrina. The main conclusions of the evaluation are:

• In the US there is no coherent and comprehensive water resources strategy. The level of protection is marginal and the investments focus on local situations, the short-term, are cost-benefit based and aim to tame natural processes instead of move along with natural processes (build with nature). A new national emphasis on holistic water policy, with public safety as a mandatory component, is strongly required;

• The hurricane protection system was overwhelmed by a rare and major event, but it was also below current standards in performance. The system before Katrina operated based on decision making driven by competing priorities, incremental decision making and funding inadequate consideration of change and de facto far too low standards;

• A national cultural malady exist, in which no clear standard for planning, design and development of public infrastructure for water resources is apparent and where new knowledge is incorporated too slow and solutions are optimised based on short-term gains instead of long-term requirements. Life cycle solutions are important to the future and the 100-year standard (once in 100 year a heavy storm may break a dike through) is far too risky for a continued vitality of the economy;

• Man made measures alone cannot sufficiently reduce risk for vulnerable areas. Natural processes, like marshes, mangroves or barrier islands, need to be integral to a systems strategy for risk reduction;

• A lack of resilience of the protection system caused major losses and ultimate flooding;

Fig. 3.58 Pre-Katrina floodwalls (Source: Russo et al. 2008)

• As the risks increase along the coastline, both due to the increase of severe hazards as due to an increasing number of people and property being allowed to reside at risky places, the changing hazard cannot be treated, but reduce the exposure of people and property to the hazard lies within reach. The dichotomy between land use authorities and the dependence on continuous development prevents the right actions taken;

• Further research is necessary to understand the way to work with nature rather than control it. The art of building and sustaining natural environment is especially important;

• Current policy and practice does not deal with change. A more anticipatory and adaptive approach is desirable.

These conclusions exceed current practice. The task of USACE to maintain and realise a coastal protection includes a standard of 1:100. This standard, in the evaluation described as far too low, can be partly explained by more intense natural forces, but does not meet the standards in, for instance, the Netherlands (1:10,000) (Trouw, 2008). And despite the fact that most of the 560 km are meeting these standards again, an integrated approach as proposed by the evaluation is yet far way. Current practice is to protect people and property by floodwalls, simple concrete walls, and not with broad green dikes, which deliver more protection. The main causes of breakthroughs during Katrina were caused by malfunctioning floodwalls (Fig. 3.58). After Katrina they were strengthened (Fig. 3.59)

Another measure is used to safeguard railroad underpasses. A U-levee is realised, which is capable of preventing water flooding from one side or the other (Fig. 3.60).

Immediately after Katrina these measures were implemented at a city level (Fig. 3.61) and in neighbourhoods (Fig. 3.62)

These measures reinforce the pre Katrina standards, but the USACE is aware of the fact that these measures alone does not reduce the risk for the people if another

Fig. 3.59 Post-Katrina floodwalls (Source: Russo et al., 2008)
Fig. 3.60 U-levee, implemented under a railroad underpass (Source: LACPR, 2007)

Katrina happens today. Therefore the water management needs to be viewed at a higher level of scale. The so-called hurricane highway, which allows water from the Gulf of Mexico to strengthen and flood into the city of New Orleans, asks for a fundamental solution. A Dutch partnership advises USACE which combination of measures can be taken to increase the level of protection, both for the Louisiana coast as for New Orleans (Dircke, 2008). The first measure to be taken is to strengthen and heighten the dikes. The second type of measures is more fundamental. For two important navigation channels storm surge closures are proposed: the Inner Harbour Navigation Channel and the Gulf Intra-coastal Water Way (Fig. 3.63). Several closure types are compared on protection level, size of protected area, costs, effects on the environment and desired type of navigation.

Fig. 3.61 New Orleans hurricane risk reduction system (Source: LACPR, 2007)
Fig. 3.62 Inner levee plan for New Orleans (Source LACPR, 2007)

The types of proposed solutions not only stabilise the delta and the coastal zone, they protect the city of New Orleans as well (Dijkman, 2007). The preferred strategy (Fig. 3.64) to protect the area consists of the following measures:

Fig. 3.63 Storm Surge Closure in the Gulf Intracoastal Water Way (Source: Trouw, 2008)
Fig. 3.64 Preferred strategy (Source: Dijkman, 2007)

1. Improve the organisation of flood risk management;

2. Upgrade the levee system in New Orleans to a 1:1000 level and enclosing it with a belt of fresh water cypress tree swamps;

3. Create in the Pontchartrain Basin a semi-open system, with a levee and several gates or keep it open and heighten the levees along the Lake Pontchartrain.

Stabilise the existing wetlands and create new wetlands to reduce surges and waves and to close the belt of fresh water swamps 4. Create an open system in the Barataria basin with wetland stabilisation measures.

Due to the combination of civil engineered waterworks and ecomorphological measures natural processes are given the change to contribute to the resilience of the area and the safety level is improved.

3.5.3 State of Louisiana Master Plan

The State of Louisiana carried out a Master Plan (CPRA, 2008) for the entire coast of Louisiana (Fig. 3.65).

In order to find the most severe weaknesses an analysis was conducted on the hurricane surge elevations in the area (Fig. 3.66).

In the Master Plan this information was used to raise awareness that protection levels should be heightened and a protection strategy was needed. The following the main objectives were defined:

1. A conceptual vision of a sustainable coast needs to be created;

2. Long-term and comprehensive coastal protection and restoration must be achieved;

3. Discrete areas of action need to be integrated: flood protection and wetland restoration

LACPR General Project Area

LACPR General Project Area

Fig. 3.65 Project area (Source: CPRA, 2008)
Fig. 3.66 (continued)

Figura S: Múltipla Une» Di dátame concept {adapted from g ra pille produced by Iho i

Fig. 3.67 Multiple lines of defence (Source: CPRA, 2GGS)

Figura S: Múltipla Une» Di dátame concept {adapted from g ra pille produced by Iho i

Fig. 3.67 Multiple lines of defence (Source: CPRA, 2GGS)

Fig. 3.68 Restoring and maintaining critical landscape features (Source: CPRA, 2008)

The Master Plan consists of maps and explanations as well as a management strategy for implementation.

The need for realising the Master Plan is acute. Every year the coast of Louisiana is losing land and this causes a risk for pipelines, navigation channels, fisheries, century old settlements and priceless ecosystems. These problems are strongly intensified by hurricanes Katrina and Rita.

The Mater Plan is a living document, which can be adjusted if circumstances change. It lays emphasis on three elements:

1. A sustainable landscape is a prerequisitive for both storm protection and ecological restoration;

2. Change is inevitable;

3. Hurricane protection relies on a strategic planning concept: a contains multiple lines of defence (Fig. 3.67)

The integral Masterplan thus aims to reduce risk to economic assets, to restore sustainability to the coastal ecosystem, to maintain a diverse array of habitats for fish and wildlife and to sustain the unique heritage and culture of the region.

The measures in the Masterplan belong to three categories: Mississippi Delta, Atchafalaya Delta and Chenier Plain and Hurricane protection.

The restoration of sustainability to the Mississippi River Delta aims to reconnect the Mississippi River to the wetlands through controlled diversions in order to restore flows of water through the wetlands so that the ecosystem can retain sediment and nutrients. This can be done through the following measures (Fig. 3.68):

• Land building restorations will create new delta lobes and nourish existing wetlands;

• Land sustaining diversions reduce losses and restores the sustainability of existing wetlands;

• Marsh restoration with dredged material;

• Use existing navigation channels, which can distribute channel water to remote areas of the coast;

• Barrier shoreline restoration to serve as a first line of defence and form the habitat for endangered animal species and birds;

• Ridge habitat restoration are deflecting storm surge and support woody vegetation and provide habitat for a variety of wildlife species;

• Shoreline stabilisation to preserve the boundaries of water-bodies and protect the hinterland;

• Closure of the Mississippi River Gulf outlet to deep draft navigation and for the construction of a closure dam. It will restore the integrity of the Bayou LaLoutre ridge and use the remainder of the channel to convey fresh water.

The Restoring of sustainability of the Atchafalaya river delta and Chenier plain aims to enhance the land building capacity of the Atchafalaya River Delta and prevent saltwater to penetrate inland in the Chanier Plain by taking the following measures:

• Managing water and sediment to reduce the impact of saltwater intrusion;

• Marsh restoration using dredged material in order to create new land;

• Barrier shoreline restoration to maintain the integrity of the shoreline and protect interior marshes, while allowing tidal exchange;

• Lake shoreline stabilisation to prevent catastrophic effects after breeching and prevent wave induced erosion of marsh, cheniers and coastal prairie.

Hurricane protection needs to protect people and property proportional to the apparent assets.

• The entire system must be considered to deliver water, sediments and nutrients to wetlands, improvement of the hydrology, to reduce flooding in low lying communities and prevent flood water from being trapped in the system;

• Non structural measures like keeping wet areas wet, evacuation plans and maintenance of evacuation routes as well as adjustments of buildings must be carried out;

• Focused structural solutions must be implemented by building hurricane protection systems in Lake Pontchartrain (Fig. 3.69), Barataria Basin (Fig. 3.70), Plaquemines Parish (Fig. 3.71), Terrebonne Parish, LA Highway Corridor, Aca-diana and Chenier Plain.

Figure 15. Lake PwiKhanraln Baffler Alfgnrfxf^i fïLako Borgne

Fig. 3.69 Hurricane protection: Lake Pontchartrain Barrier Allignment options: Interior at Golden Triangle, Rim of Lake Borgne, Lake Borgne (Source: CPRA, 2008)

Fig. 3.69 (continued)

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