Browsing by Subject "Wetlands"
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Item Open Access AN EVALUATION OF WETLAND COMPENSATORY MITIGATION IN THE NEW YORK GREAT LAKES BASIN(2006-12) Chin, StephanieAn ongoing priority for EPA’s Wetlands Program is to determine the effectiveness of compensatory mitigation at offsetting impacts to wetlands and meeting the goal of ‘no net loss’ of wetland functions. The Army Corps of Engineers is also tasked to ensure that required compensatory mitigation actions are being taken for impacts to waters of the United States under the Clean Water Act-Section 404 permit program. The purpose of this study was to provide information about the success of compensatory creation and restoration mitigation efforts for permitted impacts in the New York Great Lakes region of the Buffalo Corps District. A review of the District’s records was performed in order to identify where Section 404 wetland impacts have been occurring and to examine the extent to which wetland mitigation sites have been successful in terms of acreage achieved, established plant community type, and invasive species colonization. In addition, percent cover of invasive species at mitigation sites was examined against landscape setting to see whether this was related to success. A number of recommendations were made concerning possible improvements to permitting, data management, and mitigation project monitoring and reporting. At the onset of this study, data retrieval proved to be difficult because project files were often incomplete. At mitigation sites, a disproportionate amount of emergent and emergent/open water systems were proposed to replace scrub-shrub and forested communities. Thus, functional replacement may be unlikely in those cases. Percent cover of invasive species increased with urbanization, possibly reflecting effects of disturbance on fostering invasive plant species colonization. Success in obtaining no net wetland loss is reliant upon the ability to issue permits with conditions that ensure that functions are properly replaced, and also on continued follow up compliance monitoring of these mitigation projects.Item Open Access An Inventory of the Wetlands Impacted by the U.S. Navy's Proposed OLF Site in Gates County, North Carolina(2009-04-24T12:57:54Z) Allie, AnnaThe US Navy has proposed construction of an Outlying Landing Field (OLF) for carrier-landing practice, at one of five potential sites in North Carolina and Virginia. The proposed Sandbanks site in Gates County, NC is opposed by the Citizens Against OLF, who asked the Duke Environmental Law and Policy Clinic to evaluate possible damages to the area by drafting an Environmental Impact Statement. This project will contribute to that EIS by evaluating the site’s hydrology and wetlands using GIS analysis. Results of examinations of the wetlands’ ecosystem services indicate large areas of important wetlands on and near the site. The individual results (buffering capacity, runoff estimates, and habitat quality) are integrated into a single product that can be compared to the North Carolina Coastal Region Evaluation of Wetland Significance (NC CREWS). This comparison shows a larger area of high significance wetlands in the NC CREWS rating due to depth of the analysis, among other factors. There is ample evidence of high wetland significance at the Gates County site.Item Open Access Coastal Plain Pond Vegetation Patterns: Tracking Changes Across Space and Time(2010) ODea, ClaireCoastal plain ponds are an understudied and threatened wetland ecosystem with many unique environmental attributes. Research in these ponds can investigate species-environment relationships, while simultaneously providing ecosystem-specific information crucial to their continued conservation and management. This dissertation explores patterns in coastal plain pond vegetation composition and species-environment relationships across space, through time, and in the seed bank and standing vegetation.
In a two-year field study at 18 coastal plain ponds across the island of Martha's Vineyard, Massachusetts, I investigated species-environment relationships within and among ponds. I identified vegetation species presences and abundances within 1 m2 quadrats, which ran continuously along transects established perpendicular to the water's edge. Species data were analyzed against local and landscape-scale environmental data. I also conducted a one-year seed bank study in which sediments from four coastal plain ponds were incubated in growth chambers and composition was compared to the standing vegetation. One hundred and thirty-four plant species were identified during vegetation sampling and 38 species were identified from incubated sediments.
I found significant compositional change across space in response to environmental gradients, with patterns in species composition occurring at both local and landscape scales. Elevation was the only local factor strongly correlated with species composition. Significant landscape-scale environmental factors included surficial geology and pond water salinity. Species composition was significantly correlated with hydrologic regime in 2005 but not in 2006. Overall patterns in vegetation species composition and abundance were more closely related to landscape-scale environmental variables than to local environmental variables.
I also found that coastal plain ponds undergo significant compositional change from one year to the next. Interannual variability disproportionately affected certain ponds and quadrats more than others, highlighting patterns in the relationships between compositional change and environmental attributes. Specifically, ephemeral ponds, ponds located on the moraine, ponds with high specific conductance values, and quadrats located closer to the waterline exhibited greater compositional change from 2005 to 2006 than permanent ponds, ponds located on the outwash plain, ponds with low specific conductance values, and quadrats located further from the waterline.
Finally, I found that coastal plain ponds exhibit a low degree of similarity between composition in sediments and standing vegetation. More species were identified in the standing vegetation than in the seed bank, and in most cases average species richness per quadrat was higher in the standing vegetation than in the seed bank. Seed bank and standing vegetation samples from ponds with different surficial geology were compositionally distinct. Seed bank samples from permanent and ephemeral ponds were compositionally distinct whereas standing vegetation samples were not.
Item Open Access Connecting differential responses of native and invasive riparian plants to climate change and environmental alteration.(Ecol Appl, 2015-04) Flanagan, Neal E; Richardson, Curtis J; Ho, MengchiClimate change is predicted to impact river systems in the southeastern United States through alterations of temperature, patterns of precipitation and hydrology. Future climate scenarios for the southeastern United States predict (1) surface water temperatures will warm in concert with air temperature, (2) storm flows will increase and base flows will decrease, and (3) the annual pattern of synchronization between hydroperiod and water temperature will be altered. These alterations are expected to disturb floodplain plant communities, making them more vulnerable to establishment of invasive species. The primary objective of this study is to evaluate whether native and invasive riparian plant assemblages respond differently to alterations of climate and land use. To study the response of riparian wetlands to watershed and climate alterations, we utilized an existing natural experiment imbedded in gradients of temperature and hydrology-found among dammed and undammed rivers. We evaluated a suite of environmental variables related to water temperature, hydrology, watershed disturbance, and edaphic conditions to identify the strongest predictors of native and invasive species abundances. We found that native species abundance is strongly influenced by climate-driven variables such as temperature and hydrology, while invasive species abundance is more strongly influenced by site-specific factors such as land use and soil nutrient availability. The patterns of synchronization between plant phenology, annual hydrographs, and annual water temperature cycles may be key factors sustaining the viability of native riparian plant communities. Our results demonstrate the need to understand the interactions between climate, land use, and nutrient management in maintaining the species diversity of riparian plant communities. Future climate change is likely to result in diminished competitiveness of native plant species, while the competitiveness of invasive species will increase due to anthropogenic watershed disturbance and accelerated nutrient and sediment export.Item Open Access Discharge competence and pattern formation in peatlands: a meta-ecosystem model of the Everglades ridge-slough landscape.(PLoS One, 2013) Heffernan, James B; Watts, Danielle L; Cohen, Matthew JRegular landscape patterning arises from spatially-dependent feedbacks, and can undergo catastrophic loss in response to changing landscape drivers. The central Everglades (Florida, USA) historically exhibited regular, linear, flow-parallel orientation of high-elevation sawgrass ridges and low-elevation sloughs that has degraded due to hydrologic modification. In this study, we use a meta-ecosystem approach to model a mechanism for the establishment, persistence, and loss of this landscape. The discharge competence (or self-organizing canal) hypothesis assumes non-linear relationships between peat accretion and water depth, and describes flow-dependent feedbacks of microtopography on water depth. Closed-form model solutions demonstrate that 1) this mechanism can produce spontaneous divergence of local elevation; 2) divergent and homogenous states can exhibit global bi-stability; and 3) feedbacks that produce divergence act anisotropically. Thus, discharge competence and non-linear peat accretion dynamics may explain the establishment, persistence, and loss of landscape pattern, even in the absence of other spatial feedbacks. Our model provides specific, testable predictions that may allow discrimination between the self-organizing canal hypotheses and competing explanations. The potential for global bi-stability suggested by our model suggests that hydrologic restoration may not re-initiate spontaneous pattern establishment, particularly where distinct soil elevation modes have been lost. As a result, we recommend that management efforts should prioritize maintenance of historic hydroperiods in areas of conserved pattern over restoration of hydrologic regimes in degraded regions. This study illustrates the value of simple meta-ecosystem models for investigation of spatial processes.Item Open Access Ecological Assessment of the Flamingo Mangroves, Guanacaste, Costa Rica(2011-04-29) Fedak, Derek; Windstein, MarieMangroves are tropical and subtropical ecosystems found in intertidal zones that provide vital ecosystem services including sustenance of commercially important fishery species, improvement of coastal water quality through nutrient cycling and sediment interception, and protection of coastal communities from storm surge and erosion. However, land use conversion and water pollution are threatening these ecosystems and their associated services worldwide. This master’s project conducted an ecological assessment on a mangrove forest adjoining the property of the Flamingo Beach Resort and Spa in Playa Flamingo, located in the Guanacaste province of Costa Rica. The project analyzed vegetation health, water and soil quality, bird species richness, and identified threats to the forest. It also assessed several options for the resort’s development of ecotourism, such as community involvement, the construction of an educational boardwalk, and the creation of a vegetation buffer adjoining the mangroves. The results indicate that the Flamingo Mangroves are generally in a healthy state. Vegetation structure like canopy height, biomass, vegetation importance values, and species distribution compares well with previous ecological studies on mature tidal mangroves. The ecosystem supports 42 resident bird species and likely up to 30 migratory species. However, water quality is a major concern, which reported elevated levels of nitrogen and phosphorus through runoff and discharged wastewater in the northern section of the forest. Additionally, the western edge of the forest adjoining the beach road is frequently disturbed by automotive traffic and runoff, displaying reduced or stunted vegetation and sandy soil. This report contains several recommendations on how to preserve the mangroves by improving water quality, reducing physical and chemical disturbances, and engaging the community. The results of the project will be incorporated into our client‘s and Flamingo community‘s future management practices to conserve the Flamingo Mangroves and emphasize the value of this ecosystem.Item Open Access Ecological restoration of rich fens in Europe and North America: from trial and error to an evidence-based approach.(Biol Rev Camb Philos Soc, 2015-02) Lamers, Leon PM; Vile, Melanie A; Grootjans, Ab P; Acreman, Mike C; van Diggelen, Rudy; Evans, Martin G; Richardson, Curtis J; Rochefort, Line; Kooijman, Annemieke M; Roelofs, Jan GM; Smolders, Alfons JPFens represent a large array of ecosystem services, including the highest biodiversity found among wetlands, hydrological services, water purification and carbon sequestration. Land-use change and drainage has severely damaged or annihilated these services in many parts of North America and Europe; restoration plans are urgently needed at the landscape level. We review the major constraints on the restoration of rich fens and fen water bodies in agricultural areas in Europe and disturbed landscapes in North America: (i) habitat quality problems: drought, eutrophication, acidification, and toxicity, and (ii) recolonization problems: species pools, ecosystem fragmentation and connectivity, genetic variability, and invasive species; and here provide possible solutions. We discuss both positive and negative consequences of restoration measures, and their causes. The restoration of wetland ecosystem functioning and services has, for a long time, been based on a trial-and-error approach. By presenting research and practice on the restoration of rich fen ecosystems within agricultural areas, we demonstrate the importance of biogeochemical and ecological knowledge at different spatial scales for the management and restoration of biodiversity, water quality, carbon sequestration and other ecosystem services, especially in a changing climate. We define target processes that enable scientists, nature managers, water managers and policy makers to choose between different measures and to predict restoration prospects for different types of deteriorated fens and their starting conditions.Item Open Access Emerging contaminant or an old toxin in disguise? Silver nanoparticle impacts on ecosystems.(Environ Sci Technol, 2014-05-06) Colman, Benjamin P; Espinasse, Benjamin; Richardson, Curtis J; Matson, Cole W; Lowry, Gregory V; Hunt, Dana E; Wiesner, Mark R; Bernhardt, Emily SThe use of antimicrobial silver nanoparticles (AgNPs) in consumer-products is rising. Much of these AgNPs are expected to enter the wastewater stream, with up to 10% of that eventually released as effluent into aquatic ecosystems with unknown ecological consequences. We examined AgNP impacts on aquatic ecosystems by comparing the effects of two AgNP sizes (12 and 49 nm) to ionic silver (Ag(+); added as AgNO3), a historically problematic contaminant with known impacts. Using 19 wetland mesocosms, we added Ag to the 360 L aquatic compartment to reach 2.5 mg Ag L(-1). Silver treatments and two coating controls were done in triplicate, and compared to four replicate controls. All three silver treatments were toxic to aquatic plants, leading to a significant release of dissolved organic carbon and chloride following exposure. Simultaneously, dissolved methane concentrations increased forty-fold relative to controls in all three Ag treatments. Despite dramatic toxicity differences observed in lab studies for these three forms of Ag, our results show surprising convergence in the direction, magnitude, and duration of ecosystem-scale impacts for all Ag treatments. Our results suggest that all forms of Ag changed solute chemistry driving transformations of Ag which then altered Ag impacts.Item Open Access Emerging Issues in Wetland Loss Mitigation: A Policy Analysis in the Tar-Pamlico Basin(2006) Hill, TamaraEcological functions of wetlands and streams provide valuable services to human societies, but conflicting societal objectives at times place greater value on conversion or destruction than on preservation of wetlands. Therefore, it is imperative that regulatory structures provide a system for environmental decision makers to weigh available science, stakeholder input, and economic factors in determining how to minimize and mitigate loss of these resources. This study utilized an environmental policy analysis framework to evaluate the success of North Carolina’s wetland management system in achieving these goals, and to locate programmatic components for which performance could be improved. Comparison with past analyses revealed that the state’s newest mitigation mechanism, the Ecosystem Enhancement Program, demonstrated high-level or enhanced performance over its first two years of operation in efficiency, the ability to incorporate scientific advancements, transparency, and watershed planning. Areas for continued improvement were identified as incorporating a functional assessment methodology into wetland evaluation for determining mitigation requirements and evaluating mitigation success, increasing the length of monitoring for restored and created wetland and stream projects, enhancing data availability and clarity, and applying a watershed approach in directing development toward areas of least environmental damage.Item Open Access Environmental conditions influence the plant functional diversity effect on potential denitrification.(PLoS One, 2011-02-02) Sutton-Grier, Ariana E; Wright, Justin P; McGill, Bonnie M; Richardson, CurtisGlobal biodiversity loss has prompted research on the relationship between species diversity and ecosystem functioning. Few studies have examined how plant diversity impacts belowground processes; even fewer have examined how varying resource levels can influence the effect of plant diversity on microbial activity. In a field experiment in a restored wetland, we examined the role of plant trait diversity (or functional diversity, (FD)) and its interactions with natural levels of variability of soil properties, on a microbial process, denitrification potential (DNP). We demonstrated that FD significantly affected microbial DNP through its interactions with soil conditions; increasing FD led to increased DNP but mainly at higher levels of soil resources. Our results suggest that the effect of species diversity on ecosystem functioning may depend on environmental factors such as resource availability. Future biodiversity experiments should examine how natural levels of environmental variability impact the importance of biodiversity to ecosystem functioning.Item Open Access Hidden Loss of Wetlands in China.(Current biology : CB, 2019-09) Xu, Weihua; Fan, Xinyue; Ma, Jungai; Pimm, Stuart L; Kong, Lingqiao; Zeng, Yuan; Li, Xiaosong; Xiao, Yi; Zheng, Hua; Liu, Jianguo; Wu, Bingfang; An, Li; Zhang, Lu; Wang, Xiaoke; Ouyang, ZhiyunTo counter their widespread loss, global aspirations are for no net loss of remaining wetlands [1]. We examine whether this goal alone is sufficient for managing China's wetlands, for they constitute 10% of the world's total. Analyzing wetland changes between 2000 and 2015 using 30-m-resolution satellite images, we show that China's wetlands expanded by 27,614 km2 but lost 26,066 km2-a net increase of 1,548 km2 (or 0.4%). This net change hides considerable complexities in the types of wetlands created and destroyed. The area of open water surface increased by 9,110 km2, but natural wetlands-henceforth "marshes"-decreased by 7,562 km2. Of the expanded wetlands, restoration policies contributed 24.5% and dam construction contributed 20.8%. Climate change accounted for 23.6% but is likely to involve a transient increase due to melting glaciers. Of the lost wetlands, agricultural and urban expansion contributed 47.7% and 13.8%, respectively. The increase in wetlands from conservation efforts (6,765 km2) did not offset human-caused wetland losses (16,032 km2). The wetland changes may harm wildlife. The wetland loss in east China threatens bird migration across eastern Asia [2]. Open water from dam construction flooded the original habitats of threatened terrestrial species and affected aquatic species by fragmenting wetland habitats [3]. Thus, the "no net loss" target measures total changes without considering changes in composition and the corresponding ecological functions. It may result in "paper offsets" and should be used carefully as a target for wetland conservation.Item Open Access Investigating the Spatial and Quantitative Impacts of Stream Restoration on Riparian Soil Properties in the North Carolina Piedmont(2009-04-23T23:58:53Z) Unghire, JoshuaOne of the prime objectives of restoration is to alter the biotic and abiotic components of a system in a way so as to promote the revitalization of ecosystem functions and characteristics similar to those of undisturbed ecosystems of the same type. In stream restoration, this involves reestablishing a hydrologic regime favorable to the colonization of hydrophytic vegetation and the development of hydric soils. Soil properties of riparian floodplains are largely influenced by connectivity with the stream channel, but can also be affected by the physical process of restoration itself. The objective of this study was to quantify the spatial impacts of restoration efforts on soil properties by comparing soils collected before and four years after a riparian restoration in the piedmont of North Carolina. Few studies have assessed spatial variability both before and after restoration. We used a spatially discrete sampling design which allowed for the assessment of the spatial variability of soil properties: soil organic matter content (SOM), extractable inorganic nitrogen (NO2-NO3) and extractable inorganic phosphorus (Pex). The spatial patterns were modeled with semi-variance analysis and kriging. We also used statistical analysis to compare the changes in abundance of soil properties. The mean SOM significantly decreased after restoration, whereas the mean Pex significantly increased. Concentrations of NO2-NO3 were not significantly different in the post-restoration sampling compared to pre-restoration levels. Our results indicate that restoration processes have resulted in the spatial homogenization of SOM and Pex, removing intrinsic soil patchiness. The loss of this spatial patterning along with soil organic matter pools represent a negative impact of restoration on important ecosystem characteristics which may have taken extensive lengths of time to develop. Further research over longer time scales will be needed to assess whether these losses represent a short-term setback in the development of the ecosystem, or a long-term alteration of the ecosystems characteristics. While disturbance from restoration processes may be unavoidable to some extent, the potential negative impact of these activities is important to understand as to avoid excessive disturbance.Item Open Access Legacy source of mercury in an urban stream-wetland ecosystem in central North Carolina, USA.(Chemosphere, 2015-11) Deonarine, Amrika; Hsu-Kim, Heileen; Zhang, Tong; Cai, Yong; Richardson, Curtis JIn the United States, aquatic mercury contamination originates from point and non-point sources to watersheds. Here, we studied the contribution of mercury in urban runoff derived from historically contaminated soils and the subsequent production of methylmercury in a stream-wetland complex (Durham, North Carolina), the receiving water of this runoff. Our results demonstrated that the mercury originated from the leachate of grass-covered athletic fields. A fraction of mercury in this soil existed as phenylmercury, suggesting that mercurial anti-fungal compounds were historically applied to this soil. Further downstream in the anaerobic sediments of the stream-wetland complex, a fraction (up to 9%) of mercury was converted to methylmercury, the bioaccumulative form of the metal. Importantly, the concentrations of total mercury and methylmercury were reduced to background levels within the stream-wetland complex. Overall, this work provides an example of a legacy source of mercury that should be considered in urban watershed models and watershed management.Item Open Access Local Wetland Protection in the Hudson Valley(2010-04-29T18:45:26Z) Griggs, DavidA 2001 US Supreme Court decision limiting the scope of Section 404 of the Clean Water Act by eliminating federal authority over isolated wetlands has shifted the burden for regulating wetlands to states and local governments. Given New York State’s current wetland regulations, the gap in the federal wetland regulations can not be filled at the state level. This study centered on the question of whether local wetland protection ordinances can fill this regulatory gap. Local wetland protection laws in the Hudson Valley were surveyed to provide insight into how many municipalities have local wetland protection ordinances, and to provide data as to the level of wetland protection. Of the 240 towns and villages located in the 10 counties in the Hudson Valley, only 30 percent have local wetland protection laws. Most of these municipalities also regulate buffers around wetlands and watercourses. Almost half of the municipalities with ordinances regulate wetland areas down to no minimum size threshold which includes isolated wetlands, which therefore exceeds federal wetland regulations and fills this regulatory gap. The study also included an analysis of municipalities that recently have passed, failed or is currently pursuing wetland protection ordinances to determine what challenges and issues were faced and what elements of the law required compromising. Officials agreed getting the public involved early in the procedures was the most important issue. Political alignment was proved to determine the likelihood of a municipality to have such ordinances. Municipalities that failed to implement wetland protection regulations appeared to result from misinformation or a lack of information provided to the public. The most controversial element of these regulations is the buffer areas. Most towns had to compromise on the buffer areas. A grandfathering clause was also significant in getting the public to endorse the new regulations. Typically, activities surrounding residential and agricultural properties were important issues. Several recently passed wetland and watercourse regulations were the result of public concern for health and safety issues such as flooding events.Item Open Access Long-term transformation and fate of manufactured ag nanoparticles in a simulated large scale freshwater emergent wetland.(Environ Sci Technol, 2012-07-03) Lowry, GV; Espinasse, BP; Badireddy, AR; Richardson, CJ; Reinsch, BC; Bryant, LD; Bone, AJ; Deonarine, A; Chae, S; Therezien, M; Colman, BP; Hsu Kim, H; Bernhardt, ES; Matson, CW; Wiesner, MRTransformations and long-term fate of engineered nanomaterials must be measured in realistic complex natural systems to accurately assess the risks that they may pose. Here, we determine the long-term behavior of poly(vinylpyrrolidone)-coated silver nanoparticles (AgNPs) in freshwater mesocosms simulating an emergent wetland environment. AgNPs were either applied to the water column or to the terrestrial soils. The distribution of silver among water, solids, and biota, and Ag speciation in soils and sediment was determined 18 months after dosing. Most (70 wt %) of the added Ag resided in the soils and sediments, and largely remained in the compartment in which they were dosed. However, some movement between soil and sediment was observed. Movement of AgNPs from terrestrial soils to sediments was more facile than from sediments to soils, suggesting that erosion and runoff is a potential pathway for AgNPs to enter waterways. The AgNPs in terrestrial soils were transformed to Ag(2)S (~52%), whereas AgNPs in the subaquatic sediment were present as Ag(2)S (55%) and Ag-sulfhydryl compounds (27%). Despite significant sulfidation of the AgNPs, a fraction of the added Ag resided in the terrestrial plant biomass (~3 wt % for the terrestrially dosed mesocosm), and relatively high body burdens of Ag (0.5-3.3 μg Ag/g wet weight) were found in mosquito fish and chironomids in both mesocosms. Thus, Ag from the NPs remained bioavailable even after partial sulfidation and when water column total Ag concentrations are low (<0.002 mg/L).Item Open Access Nature-based Urban Flood Resilience: a policy analysis of natural flood mitigation measures in sea level rise planning in New Orleans, New York City, and San Francisco(2017-08-18) Myers, MichelleSea level rise (SLR) and severe weather events have already exposed the vulnerability of coastal cities to flood events. Regional planning bodies are developing comprehensive plans to build resiliency utilizing both hardened and natural flood mitigation measures. While the plans use living shorelines and wetland restoration to buffer coastal regions, land managers have uncertainty to the level of protection these measures provide and a bias to maintain hardened shorelines and levee infrastructure. In addition, there are barriers to implementation of SLR adaptation plans in permitting, funding and land tenure. Research methods for the project include a literature review of resiliency planning documents and related articles, as well as interviews with resiliency planning staff in the case study areas of New York, San Francisco, and New Orleans. Policy recommendations are made that include: standardizing economic valuation and performance matrices of natural flood barriers, simplifying agency approvals, developing managed retreat practices and project migration zones, and increasing federal funding while identifying local resources for adaptation projects.Item Open Access Physical and Program Options for the Inland Migration of Louisiana's Coastal Wetlands in Response to Relative Sea Level Rise(2012-04-26) Kemm, Melissa; Beck, Heidi; Bihler, Alicia; Perron, Douglas; Pardo, SamLouisiana contains over a third of the coastal wetlands in the contiguous US, but has seen a drastic reduction in total wetland area in the last century. This loss is especially troubling for coastal Louisiana where wetlands play a vital role in protecting and supporting the state’s economy and culture. Under natural conditions, coastal wetlands will move upland with rising sea level or sinking land. However, engineered structures and shore armoring, such as levees, seawalls, and bulkheads, impede this process. Advanced planning for wetland migration is needed to keep communities and infrastructure out of harm’s way from encroaching open water and to mitigate future wetland loss. This project investigates the potential for wetland migration in Louisiana through 1) the mapping and analysis of coastal wetland migration and 2) an examination of policy alternatives relevant to wetland migration. Wetland loss and migration was analyzed in Lafourche, St. Mary, and Vermilion parishes using the Sea Level Affecting Marshes Model (SLAMM). Moderate and less optimistic values of subsidence rates were modeled with constant global sea level rise projections to identify the impacts of dike and levee protection on wetland loss and the upland migration of coastal wetlands. The percent of wetland loss offset by wetland migration was calculated for each parish in an effort to aid in management decisions. It was found that wetland migration into dry land areas did not occur in any of the three parishes unless dike and levee protection of undeveloped dry lands was removed. The intensity of subsidence and the distribution of dry land greatly impact the overall benefits of allowing coastal wetlands to migrate into dry lands. This observation was exemplified in Lafourche Parish, which has a limited distribution of dry land and was modeled using higher subsidence rates than those found in both St. Mary and Vermilion parishes. Not only was the net loss of wetlands greater when dike and levee protection was removed in Lafourche Parish, but the total amount of wetland gain by means of wetland migration was incapable of offsetting a significant amount wetland loss. The policy analysis was developed with respect to the criteria and framework of Louisiana’s Comprehensive Master Plan for a Sustainable Coast and for use in an exploratory model. Considering the results of the geospatial analysis within this report, a model was developed to assist in management decisions regarding the migration of coastal wetlands across Louisiana’s geophysically and socio-economically variable coastline. The model was constructed using five main criteria to assess six different policy alternatives. Policy criteria included wetland migration, flood risk, equity, adaptability, and political feasibility, and the policy alternatives assessed were rolling easements, density restrictions, transferable development rights, conservation easements, defeasible estates and voluntary acquisition. Specific recommendations were made with the goal of developing an equitable and efficient wetland migration policy capable of complementing and improving current coastal management plans.Item Open Access Physical and Program Options for the Inland Migration of Louisiana's Coastal Wetlands in Response to Relative Sea Level Rise(2012-04-26) Pardo, Sam; Beck, Heidi; Bihler, Alicia; Kemm, Melissa; Perron, DouglasLouisiana contains over a third of the coastal wetlands in the contiguous U.S., but has seen a drastic reduction in total wetland area in the last century. This loss is especially troubling for coastal Louisiana where wetlands play a vital role in protecting and supporting the state’s economy and culture. Under natural conditions, coastal wetlands will move upland with rising sea level or sinking land. However, engineered structures and shore armoring, such as levees, seawalls, and bulkheads, impede this process. Advanced planning for wetland migration is needed to keep communities and infrastructure out of harm’s way from encroaching open water and to mitigate future wetland loss. This project investigates the potential for wetland migration in Louisiana through 1) the mapping and analysis of coastal wetland migration and 2) an examination of policy alternatives relevant to wetland migration. Wetland loss and migration were analyzed in Lafourche, St. Mary, and Vermilion parishes using the Sea Level Affecting Marshes Model. Moderate and less optimistic values of subsidence rates were modeled with constant global sea level rise projections to identify the impacts of dike and levee protection on wetland loss and the upland migration of coastal wetlands. The percent of wetland loss offset by wetland migration was calculated for each parish in an effort to aid in management decisions. It was found that wetland migration into dry land areas did not occur in any of the three parishes unless dike and levee protection of undeveloped dry lands was removed. The intensity of subsidence and the distribution of dry land greatly impact the overall benefits of allowing coastal wetlands to migrate into dry lands. This observation was exemplified in Lafourche Parish, which has a limited distribution of dry land and was modeled using higher subsidence rates than those found in both St. Mary and Vermilion parishes. Not only was the net loss of wetlands greater when dike and levee protection was removed in Lafourche Parish, but the total amount of wetland gain by means of wetland migration was incapable of offsetting a significant amount wetland loss. The policy analysis was developed with consideration for the framework of Louisiana’s Comprehensive Master Plan for a Sustainable Coast. An exploratory model was created to assist coastal managers and stakeholders in policy decisions regarding the migration of wetlands along Louisiana’s coastline. The model was constructed using five main criteria and six different policy alternatives. Policy criteria included wetland migration, flood risk, equity, adaptability, and political feasibility, and the policy alternatives assessed were rolling easements, density restrictions, transferable development rights, conservation easements, defeasible estates and voluntary acquisition. Applying the policy model in scenarios where dike and levee protection is removed reveals that rolling easements would only be appropriate in Vermillion or St. Mary parishes where potential for wetland migration is high. In Lafourche parish, where potential for wetland migration is low, an emphasis on minimizing flood risk suggests that transferable development rights would be the best alternative to pursue. Applying the policy model in areas where dikes and levees are present also favors transferable development rights as the optimal policy alternative. Moreover, this final demonstration suggests that a wetland migration policy can serve to address the CPRA priority of minimizing “induced risk,” while also adapting to changes in flood protection planning.Item Open Access Physical and Program Options for the Inland Migration of Louisiana’s Coastal Wetlands in Response to Relative Sea Level Rise(2012-04-26) Bihler, Alicia; Beck, Heidi; Kemm, Melissa; Pardo, Sam; Perron, DouglasLouisiana contains over a third of the coastal wetlands in the contiguous US, but has seen a drastic reduction in total wetland area in the last century. This loss is especially troubling for coastal Louisiana where wetlands play a vital role in protecting and supporting the state’s economy and culture. Under natural conditions, coastal wetlands will move upland with rising sea level or sinking land. However, engineered structures and shore armoring, such as levees, seawalls, and bulkheads, impede this process. Advanced planning for wetland migration is needed to keep communities and infrastructure out of harm’s way from encroaching open water and to mitigate future wetland loss. This project investigates the potential for wetland migration in Louisiana through 1) the mapping and analysis of coastal wetland migration and 2) an examination of policy alternatives relevant to wetland migration. Wetland loss and migration was analyzed in Lafourche, St. Mary, and Vermilion parishes using the Sea Level Affecting Marshes Model (SLAMM). Moderate and less optimistic values of subsidence rates were modeled with constant global sea level rise projections to identify the impacts of dike and levee protection on wetland loss and the upland migration of coastal wetlands. The percent of wetland loss offset by wetland migration was calculated for each parish in an effort to aid in management decisions. It was found that wetland migration into dry land areas did not occur in any of the three parishes unless dike and levee protection of undeveloped dry lands was removed. The intensity of subsidence and the distribution of dry land greatly impact the overall benefits of allowing coastal wetlands to migrate into dry lands. This observation was exemplified in Lafourche Parish, which has a limited distribution of dry land and was modeled using higher subsidence rates than those found in both St. Mary and Vermilion parishes. Not only was the net loss of wetlands greater when dike and levee protection was removed in Lafourche Parish, but the total amount of wetland gain by means of wetland migration was incapable of offsetting a significant amount wetland loss. The policy analysis was developed with respect to the criteria and framework of Louisiana’s Comprehensive Master Plan for a Sustainable Coast and for use in an exploratory model. Considering the results of the geospatial analysis within this report, a model was developed to assist in management decisions regarding the migration of coastal wetlands across Louisiana’s geophysically and socio-economically variable coastline. The model was constructed using five main criteria to assess six different policy alternatives. Policy criteria included wetland migration, flood risk, equity, adaptability, and political feasibility, and the policy alternatives assessed were rolling easements, density restrictions, transferable development rights, conservation easements, defeasible estates and voluntary acquisition. Specific recommendations were made with the goal of developing an equitable and efficient wetland migration policy capable of complementing and improving current coastal management plans.Item Open Access Quantifying and Prioritizing Opportunities for Canal Backfilling in Louisiana(2014-04-25) Pate, HaiglerCanal backfilling-degrading and replacing the spoil adjacent to canals-has a wide range of potential benefits for the restoration of Louisiana coastal wetlands, but is not incorporated into current coastwide-scale restoration plans. This report seeks to characterize backfilling opportunities using GIS analysis of publicly available datasets to quantify and prioritize the area and distribution of spoil currently suitable for use as canal backfill. I used multiple filters to select backfillable spoil features based on the stability of the surrounding landscape, feature size, and proximity to Congressionally-authorized navigation channels or active oil and gas wells. Even this much-reduced extent of spoil indicated significant opportunities for backfilling distributed throughout the Louisiana coast. The Barataria, Mermentau, and Terrebonne hydrologic basins contained most of a total prioritized backfillable spoil area of approximately 10,775 hectares. The total is similar to the area of linear restoration projects included in Louisiana’s 2012 Comprehensive Master Plan for a Sustainable Coast. Coastwide canal backfilling could be accomplished for less than a third of the cost of those already-planned projects, and greater savings and performance could be achieved by combining backfilling with master plan projects whose footprints they intersect. Rough estimates of the value of wetlands that could be created through canal backfilling are $1.33 billion, or $0.14 billion per year. Estimates of the net present value of a crash program of coastwide backfilling ranged as high as $2.7 billion after 50 years.