Drawing Louisiana's New Map Addressing Land Loss in Coastal Louisiana (2006) / Chapter Skim
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6 The LCA Study and the Feasibility of Its Components
6 The LCA Study and the Feasibility of Its Components
Pages 115-144
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From page 115... ...
ele ments, including economic analysis · Provides an overview of the LCA Study's feasibility · Discusses the modeling strengths and uncertainties and recommends a protocol for future conduct of the modeling pro gram · Addresses the role of adaptive management and exam ines management alternatives · Suggests Third Delta alternatives, including a large, more southern diversion and a full abandonment of the Birdsfoot Delta The activities proposed in the LCA Study are intended to be a series of interactive efforts that develop the necessary knowledge base to inform longer-term and possibly more expansive restoration efforts, while making some near-term progress by undertaking relatively low-risk projects that will result in a tangible development of what the LCA Study refers to as near-term critical restoration features. The success of these parallel efforts to slow land loss, while developing information needed to support 115
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From page 116... ...
TABLE 6.1 LCA Study Estimated Restoration Costs Item Cost Mississippi River Gulf Outlet environmental restoration features $80,000,000 Small diversion at Hope Canal $10,645,000 Barataria Basin barrier shoreline restoration $181,000,000 Small Bayou Lafourche reintroduction $75,280,000 Medium diversion with dedicated dredging at Myrtle Grove $142,920,000 Subtotal $489,845,000 Land easements, rights of way, relocation, and disposal $178,619,000 First cost Subtotal $668,464,000 Feasibility-level decision documents $54,673,000 Preconstruction, engineering, and design $36,252,000 Engineering and design $29,018,000 Supervision and administration $68,973,000 Project monitoring $6,685,000
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From page 117... ...
b $100,000,000 Beneficial use of dredge material programb $100,000,000 Investigations of modifications of existing structures $10,000,000 Authorized total LCA Study cost $1,174,065,000 Multipurpose operation of Houma Navigation Canal Lockc -Terrebonne Basin barrier shoreline restoration $84,850,000 Maintain land bridge between Caillou Lake and Gulf of Mexico $41,000,000 Small diversion at Convent/Blind River $28,564,000 Increase Amite River Diversion Canal influence by gapping banks $2,855,000 Medium diversion at White's Ditch $35,200,000 Stabilize Gulf shoreline at Point Au Fer Island $32,000,000 Convey Atchafalaya River water to northern Terrebonne marshes $132,200,000 Modification of Caernarvon diversion $1,800,000 Modification of Davis Pond diversion $1,800,000 Subtotal $360,269,000 Land easements, rights of way, relocation, and disposal $208,100,000 First cost Subtotal $568,369,000 Feasibility-level decision documents $47,529,000 Preconstruction, engineering, and design $36,027,000 Engineering and design $45,635,000 Supervision and administration $58,673,000 Project monitoring $5,683,000 Approved projects requiring future Congressional authorization for construction $761,916,000 Mississippi River hydrodynamic study $10,250,000 Mississippi River Delta management study $15,350,000 Third Delta study $15,290,000 Chenier Plain freshwater and sediment management and allocation reassessment study $12,000,000 Acadiana Bays estuarine restoration feasibility study $7,110,000 Upper Atchafalaya Basin studyd - Large-scale and long-term studies cost Subtotal $60,000,000 Total LCA Study restoration cost $1,995,981,000 a"Conventionally authorized" refers to items proposed in the Chief's Report and authorized by Congress through the Water Resources Development Act. bProgram total costs include any estimated real estate costs for these activities.
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From page 118... ...
follows. Although these features represent the most significant component of the restoration efforts evaluated in the LCA Study, they are still only the first stage of a long-term restoration program for coastal Louisiana.
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Army Corps of Engineers, 2005b)
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(U.S. Army Corps of Engineers, 2004a)
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(U.S. Army Corps of Engineers, 2004a)
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From page 122... ...
describes these knowledge gaps as "uncertainties" and lists the following four types: · Type 1: Physical, chemical, geological, and biological baseline conditions · Type 2: Engineering concepts and operational methods · Type 3: Ecological processes, analytical tools, and ecosystem response · Type 4: Socioeconomic and political conditions and responses These knowledge gaps are real, and the proposed demonstration projects to alleviate these deficiencies are definitely valid. However, the LCA Study fails to acknowledge several other important knowledge gaps, which are discussed at some length in Chapter 7.
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From page 123... ...
, wicked unknowns, and decision-making relationships. The AEAM process is described in the LCA Study as supporting passive adaptive management, which currently occurs with Coastal Wetlands Planning, Protection, and Restoration Act (CWPPRA)
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There is no acknowledgment that major national investments are being made and will soon be accelerated in connection with the coastal ocean observing and watershed monitoring programs. Opportunities currently exist for the coastal Louisiana restoration to coordinate activities with ongoing environmental data collection efforts to avoid wasteful duplications and take advantage of resources that will be funded from outside the restoration budget.
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From page 125... ...
restoration efforts would also include a decision support system that relies on clearly defined procedures to assess knowledge gaps and develop alternatives for the decision-making process" (U.S. Army Corps of Engineers, 2004a)
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From page 126... ...
Without a clear understanding of the expected annual delivery of sediments of a particle size capable of deposition under different conditions, it is difficult to assess the area of wetlands that can be sustained or built. Average Annual Sediment Delivery to the Lower Mississippi Several investigators have reported a large reduction in the sediment load of the lower Mississippi River since 1893 (Robbins, 1977; Keown et al., 1981; Kesel, 1988, 1989, 2003)
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For example, Kesel (2003) estimates that 90 percent of overbank flooding in the lower Mississippi River had been eliminated by 1927.
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128 DRAWING LOUISIANA'S NEW MAP FIGURE 6.1 Comparison of the percentage of Mississippi River discharge flowing into the adjacent wetlands and distributary channels on the Louisiana deltaic plain for 1850 and 1990 (modified from Kesel, 2003; background maps supplied by Research Planning, Inc.)
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The recruitment of the organic component and the rates of decomposition are discussed in Chapter 2. Hydrology The cumulative effects of regulated flows through the Mississippi River Basin influence the delta region.
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2. Have reasonable procedures been employed in selecting the array of projects for the LCA Study to address wetlands and barrier island loss?
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Establishing the true, national economic significance of efforts to restore coastal wetlands in Louisiana as proposed in the LCA Study, however, must go beyond simply identifying and characterizing these components and should (1) include an analysis of how specific restoration efforts will preserve or enhance their value (i.e., some restoration efforts may have little influence on the vulnerabilities of specific components of natural and built environment in coastal Louisiana)
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From page 132... ...
Thus, the potential for reducing risk due to storm surge is more difficult to generalize. Overall, the information necessary to fully understand the economic implications of wetland loss does not currently exist.
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Two projects that should receive serious further study include the Third Delta and the complete abandonment of the active Birdsfoot Delta lobe. The LCA Study identifies both the Third Delta study and Mississippi River Delta management as large-scale, long-term concepts requiring detailed study; however, no consideration is offered for evaluating abandonment of the active Birdsfoot Delta.
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without construction and implementation of the LCA Study's five recommended restoration features. Implementing these restoration efforts would reduce this land loss by 4.4 km2 per yr (1.7 mi2 per yr)
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135 with used 2004a; Engineers, of Corps Army sec.)
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Army Corps of Engineers, 2004a. TABLE 6.3 Estimates of Average Annual River Flows and Sediment Delivery Combined Average Mississippi River and Atchafalaya River Flows in m3 Combined Mineral Sediment Delivery in per sec (yd3 per sec in parentheses)
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As noted in Chapter 2, coastal dispersal of Mississippi River sediment has been dominated more by the processes of episodic avulsion of deltaic lobes than by ocean forcings (Wright and Nittrouer, 1995)
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ENHANCING THE FEASIBILITY OF THE OVERALL APPROACH An undertaking as complex as restoring and protecting coastal Louisiana presents several challenges to the understanding of many natural and anthropogenic processes, as well as fundamental engineering design. Thus, a robust program is needed to identify key knowledge gaps as they are identified and to implement research and demonstration projects to
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From page 139... ...
, and reduce the overall costs as experience and data result in improved projections. The coastal Louisiana restoration endeavor would benefit greatly from a coordinated effort that would result from the establishment of a more robust informatics and modeling effort focusing on the lower Mississippi River.
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The S&T Program requires a more explicit statement of program responsibilities and means for setting priorities; it must be integrated more effectively into the central management structure through the adaptive management process and include better representation of social sciences and ecological processes. It is unreasonable to expect any region to have all the necessary experience and human resources to address most effectively the challenges of the magnitude represented by land loss in coastal Louisiana.
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From page 141... ...
Establishing the true, national economic significance of efforts to restore coastal wetlands in Louisiana as proposed in the LCA Study, however, must go beyond simply identifying and characterizing these components and should include an analysis of how specific restoration efforts will preserve or enhance their value (i.e., some restoration efforts may have little influence on the vulnerabilities of specific components of the natural and built environment in coastal Louisiana) and determine how the national economy would respond to their loss or degradation (e.g., what is the capacity for similar components in other regions to compensate for their loss and on what time scales?
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Cost and benefit analyses discussed in the LCA Study and in supporting documents reflect an effort to identify least-cost alternatives but do not appear to reflect a system-wide effort to maximize beneficial synergies among various projects with regard to habitat loss. The selection of any suite of individual projects in future efforts to restore coastal Louisiana should include a clear effort to maximize the beneficial, synergistic effects of individual projects to minimize or reverse future land loss.
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From page 143... ...
Taking a system-wide approach to determining contributing causes and potential approaches to reducing their adverse impact on the environmental quality of coastal Louisiana should include consideration of (1) changes in the sediment flux from the basin resulting from past dam construction on the tributaries to the Mississippi River, (2)
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