Estuary Processes and Managment - River Dynamics and Integrated River Management - page 535

In summary, goals and performance guidelines for wetland restoration should include: improvement of
hydrological environment, creation of equivalent wetland areas, replacement with the approximate
ecological community, and restoration of flora and fauna. At present, however, there is no generally
accepted comprehensive guideline for large-scale coastal wetland restoration. Despite hundreds of wetland
restoration efforts in many countries, current efforts are largely more site-specific than scientific; experience
gained in one case may not be generalized to other settings. In particular, in spite of many wetland models
developed for wetland management, many of the hypothesized relationships used in the modeling are not
confirmed. For example, little credible relationship has been found between natural-resource production
activities and biodiversity loss. A better understanding of wetland dynamics and ecological processes is
desirable. Wetland restoration efforts should also be accompanied by pre- and post-restoration monitoring
and evaluation—including the collection of the necessary hydro-meteorological data and data on the status
of vegetation, wildlife, fish, and macro-invertebrate.
8.6.2.2 Artificial Floods for Louisiana Wetlands Restoration
According to the United States Geological Survey (USGS), approximately half the original wetland habitats
in the USA have been lost over the past 200 years. The wetland degradation in Louisiana is particularly
serious; it accounts for 80% of wetland losses of USA. Between 1956 and 1990, nearly 3,460 km 2 of coastal
wetlands reverted to open water, and more than 600 km 2 of wetlands have disappeared in the last decade
(Stokstad, 2005). The wetland loss rate is about 65-91 km 2 per year, one of the highest rates of land loss
in the world.
Human activities should be responsible for the degradation and loss of wetlands in Louisiana.
Seasonal floods of Mississippi River are critical to the healthy growth of wetlands, since the infusion of
fresh sediment from floodwater may offset soil subsidence in wetlands. Unfortunately, natural floods
have been virtually eliminated by construction of massive levees, depriving wetlands of vital sediment.
Cement-lined levees in South Louisiana prevent flood water in the Mississippi River from following the
original flood route; the river sediment is transported into the Gulf of Mexico instead of allowing it to be
distributed over the coastal wetlands. In addition, excessive construction of dredged systems and flood-
control structures (for facilitating the development of recreation, residence, agriculture and industry) has
aggravated the salt water intrusion from the Gulf of Mexico, creating an environment where wetland
plants cannot survive. The US Environmental Protection Agency (USEPA) estimates that one-third of
coastal wetlands in South Louisiana will vanish by 2050, if no efforts are made to halt this trend.
As part of efforts to halt the damage to wetlands and its huge impacts on coastal ecosystem, a series of
restoration plans have been mapped out and carried out since the early 1970s. For example, 37 kilometers
upstream from New Orleans, Louisiana, the Army Corps of Engineers (USACE) has constructed the USD
120 million Davis Pond Freshwater Diversion Structure (Fig. 8.80) to deliver water from the Mississippi
River to help preserve some 130,000 hectares of Louisiana's endangered marshes of Barataria Bay,
which are suffering from sediment loss like much of coastal Louisiana (Stokstad, 2005). However, this
effort is just a tiny fraction of what is needed to restore the devastated Louisiana coastline; in reality it is
difficult to mimic nature—to operate an artificial flood with proper water discharge and sediment in the
right places. In addition, every wetland restoration project has its own impacts on the local environment
and industry—e.g., a river diversion project may impact adversely on the oyster or shrimp habitat, thus
affecting the local economy.
8.6.2.3 Kissimmee River Restoration
The Kissimmee River Restoration Program is a relatively successful example. Historically the Kissimmee
River and its surrounding floodplain, located in Central Florida, USA, comprised a group of wetlands
supporting diverse ecosystems and providing habitats to many unique species of plants and animals