Peyronnin, N.; Green, M.; Richards, C.P.; Owens, A.; Reed, D.; Chamberlain, J.; Groves, D.G.; Rhinehart, W.K., and Belhadjali, K., 2013. Louisiana's 2012 Coastal Master Plan: overview of a science-based and publicly informed decision-making process.

Louisiana is in the midst of a land loss crisis that has claimed more than 4800 km² since the 1930s. Unless aggressive, large-scale action is taken, Louisiana could lose an additional 4500 km² in the next 50 years, resulting in a projected increase in annual damages from hurricane storm surge flooding of more than $23 billion. Louisiana's 2012 Coastal Master Plan is a long-term plan with clear economic, social, and environmental benefits, such as decreasing potential damages from storm surge by $5.3 billion to $18 billion. Implementation of projects in the master plan should result in no net loss of land after 20 years and an annual net gain of land after 30 years. To develop the plan, the Coastal Protection and Restoration Authority (CPRA) utilized a state-of-the-art systems approach to coastal planning and a science-based decision-making process that resulted in a funding- and resource-constrained plan that makes the greatest progress toward achieving a sustainable coast. A series of integrated, coastwide predictive models were developed to provide data for a new planning tool used to identify the suite of projects that would make the greatest progress toward meeting the master plan objectives while considering uncertainties in future environmental conditions. Recognizing that the success of the plan hinges on stakeholder support, as well as science, the CPRA also implemented a comprehensive outreach plan to obtain input and feedback from key stakeholders and the public. The resulting plan recommends a specific list of restoration and protection projects and has achieved widespread support.

Meselhe, E.; McCorquodale, J.A.; Shelden, J.; Dortch, M.; Brown, T.S.; Elkan, P.; Rodrigue, M.D.; Schindler, J.K., and Wang, Z., 2013. Ecohydrology component of Louisiana's 2012 Coastal Master Plan: mass-balance compartment model.

Coastal Louisiana is a complex system that encompasses large expanses of wetlands interspersed with shallow bays and estuaries of varying sizes and degrees of connectivity to the Gulf of Mexico, numerous water control structures, large riverine systems, and an intricate system of natural and manmade channels. This complex system is experiencing devastating rates of land loss that have been exacerbated by subsidence and sea level rise. As part of Louisiana's 2012 Coastal Master Plan, this modeling effort utilizes an efficient mass-balance approach to provide coastwide (∼100,000 km²), long-term (∼50 y) performance projections for proposed restoration and protection measures. The model presented here provided detailed information about the spatial and temporal variability of water depth, salinity, accretion rates, deposition, and other water quality parameters across the Louisiana coastal zone. Furthermore, the model provided this information to subsequent modules in the master plan suite of models, namely, wetland morphology, vegetation, ecosystem services, and barrier shoreline morphology. Collectively, this suite of models served as an effective approach to provide valuable comparative assessments for the various proposed restoration and protection scenarios and alternatives.

Couvillion, B.R.; Steyer, G.D.; Wang, H.; Beck, H.J., and Rybczyk, J.M., 2013. Forecasting the effects of coastal protection and restoration projects on wetland morphology in coastal Louisiana under multiple environmental uncertainty scenarios.

Few landscape scale models have assessed the effects of coastal protection and restoration projects on wetland morphology while taking into account important uncertainties in environmental factors such as sea-level rise (SLR) and subsidence. In support of Louisiana's 2012 Coastal Master Plan, we developed a spatially explicit wetland morphology model and coupled it with other predictive models. The model is capable of predicting effects of protection and restoration projects on wetland area, landscape configuration, surface elevation, and soil organic carbon (SOC) storage under multiple environmental uncertainty scenarios. These uncertainty scenarios included variability in parameters such as eustatic SLR (ESLR), subsidence rate, and Mississippi River discharge. Models were run for a 2010–2060 simulation period. Model results suggest that under a “future-without-action” condition (FWOA), coastal Louisiana is at risk of losing between 2118 and 4677 km² of land over the next 50 years, but with protection and restoration projects proposed in the Master Plan, between 40% and 75% of that loss could be mitigated. Moreover, model results indicate that under a FWOA condition, SOC storage (to a depth of 1 m) could decrease by between 108 and 250 million metric tons, a loss of 12% to 30% of the total coastwide SOC, but with the Master Plan implemented, between 35% and 74% of the SOC loss could be offset. Long-term maintenance of project effects was best attained in areas of low SLR and subsidence, with a sediment source to support marsh accretion. Our findings suggest that despite the efficacy of restoration projects in mitigating losses in certain areas, net loss of wetlands in coastal Louisiana is likely to continue. Model results suggest certain areas may eventually be lost regardless of proposed restoration investment, and, as such, other techniques and strategies of adaptation may have to be utilized in these areas.

Visser, J.M.; Duke-Sylvester, S.M.; Carter, J., and Broussard, W.P., III, 2013. A computer model to forecast wetland vegetation changes resulting from restoration and protection in coastal Louisiana.

The coastal wetlands of Louisiana are a unique ecosystem that supports a diversity of wildlife as well as a diverse community of commercial interests of both local and national importance. The state of Louisiana has established a 5-year cycle of scientific investigation to provide up-to-date information to guide future legislation and regulation aimed at preserving this critical ecosystem. Here we report on a model that projects changes in plant community distribution and composition in response to environmental conditions. This model is linked to a suite of other models and requires input from those that simulate the hydrology and morphology of coastal Louisiana. Collectively, these models are used to assess how alternative management plans may affect the wetland ecosystem through explicit spatial modeling of the physical and biological processes affected by proposed modifications to the ecosystem. We have also taken the opportunity to advance the state-of-the-art in wetland plant community modeling by using a model that is more species-based in its description of plant communities instead of one based on aggregated community types such as brackish marsh and saline marsh. The resulting model provides an increased level of ecological detail about how wetland communities are expected to respond. In addition, the output from this model provides critical inputs for estimating the effects of management on higher trophic level species though a more complete description of the shifts in habitat.

Nyman, J.A.; Baltz, D.M.; Kaller, M.D.; Leberg, P.L.; Parsons Richards, C.; Romaire, R.P., and Soniat, T.M., 2013. Likely changes in habitat quality for fish and wildlife in coastal Louisiana during the next fifty years.

Louisiana's 2012 Master Plan for a sustainable coast was designed to minimize economic damage from storm surges and to maximize wetland habitat for fish and wildlife. Selecting projects for inclusion in the master plan depended partly on models that simulated the effects of management options on environmental factors that control habitat quality for fish and wildlife. We used 13 models to predict the effects of the master plan on habitat quality for fish and wildlife in coastal Louisiana. Habitat quality was predicted to change more for the Neotropical songbirds and seven other modeled species losing habitat quality with the status quo (−37%) than it was predicted to increase for five modeled species gaining habitat quality with the status quo ( 18%). The master plan was predicted to slow or negate all changes associated with the status quo. All of the modeled fish and wildlife belong to people of the state of Louisiana, people living in countries bordering the Gulf of Mexico, and to people throughout the Americas. Thus, declining fish and wildlife habitat quality in Louisiana probably will cause market and nonmarket losses, which although concentrated in Louisiana, will extend across the Americas. As funding for Louisiana's master plan is pursued, it is important to consider that almost all of the causes for net wetland losses in Louisiana are external to the owners of these wetlands but that the fish and wildlife that use these wetlands belong to and benefit people throughout the Americas.

Rivera-Monroy, V.H.; Branoff, B.; Meselhe, E.; McCorquodale, A.; Dortch, M.; Steyer, G.D.; Visser, J., and Wang, H., 2013. Landscape-level estimation of nitrogen removal in coastal Louisiana wetlands: potential sinks under different restoration scenarios.

Coastal eutrophication in the northern Gulf of Mexico (GOM) is the primary anthropogenic contributor to the largest zone of hypoxic bottom waters in North America. Although biologically mediated processes such as denitrification (Dn) are known to act as sinks for inorganic nitrogen, it is unknown what contribution denitrification makes to landscape-scale nitrogen budgets along the coast. As the State of Louisiana plans the implementation of a 2012 Coastal Master Plan (MP) to help restore its wetlands and protect its coast, it is critical to understand what effect potential restoration projects may have in altering nutrient budgets. As part of the MP, a spatial statistical approach was developed to estimate nitrogen removal under varying scenarios of future conditions and coastal restoration project implementation. In every scenario of future conditions under which MP implementation was modeled, more nitrogen () was removed from coastal waters when compared with conditions under which no action is taken. Overall, the MP increased coast-wide average nitrogen removal capacity (NRC) rates by up to 0.55 g N m⁻² y⁻¹ compared with the “future without action” (FWOA) scenario, resulting in a conservative estimate of up to 25% removal of the annual load of the Mississippi-Atchafalaya rivers (956,480 t y⁻¹). These results are spatially correlated, with the lower Mississippi River and Chenier Plain exhibiting the greatest change in NRC. Since the implementation of the MP can maintain, and in some regions increase the NRC, our results show the need to preserve the functionality of wetland habitats and use this ecosystem service (i.e. Dn) to decrease eutrophication of the GOM.

Cobell, Z.; Zhao, H.; Roberts, H.J.; Clark, F.R., and Zou, S., 2013. Surge and wave modeling for the Louisiana 2012 Coastal Master Plan.

The goal of the study was to evaluate various coastal restoration and protection projects and the associated benefits for reductions in storm surge and wave height. Efforts in numerical modeling have been made to create a database of storm surge and wave responses to a set of hypothetical storms under current and various future conditions. The ADvanced CIRCulation (ADCIRC) and the Unstructured Simulating WAves Nearshore (UnSWAN) models were selected for this study. A coarser version of the state-of-the-art, southern Louisiana, unstructured mesh was developed to reduce computational overhead while maintaining critical hydraulic features. Model outputs were reviewed and analyzed from coastwide and onshore-transect points of view. The potential benefits of restoration and protection projects proposed in the Master Plan were examined by comparing Future without Action outputs to the Master Plan outputs. Hurricane protection projects, such as levees, provide remarkable protection at their leesides but increase and redistribute surge water at their front sides. Narrow, restored landscapes, such as barrier islands or ridges, may provide wave attenuation to some extent but, in many cases, provide minimal benefits in surge level reduction. Larger-scale restoration projects, such as sediment diversions, can result in land accretion and enhance vegetation coverage, thus resulting in notable benefits associated with damping waves and storm surge and ultimately reducing risk for inland communities.

Johnson, D.R.; Fischbach, J.R., and Ortiz, D.S., 2013. Estimating surge-based flood risk with the coastal Louisiana risk assessment model.

The Coastal Louisiana Risk Assessment model (CLARA) was designed to facilitate comparisons of current and future flood risk under a variety of protection system configurations in a wide range of environmental, operational, and economic uncertainties. It builds on previous studies of coastal risk by incorporating system fragility and a larger number of future scenarios than previously analyzed. Flood depths and direct economic damage from a wide range of simulated storm events are aggregated to produce a statistical summary of coastal risk under different assumptions about future conditions. CLARA's estimates of project-level effects on flood risk reduction were used as one of the key decision drivers in selecting the risk reduction projects included in the Master Plan. Depending on the scenario, the final alternative is projected to reduce expected annual damage by approximately 60 to 80% during the next 50 years relative to a future without action and, at the same time, balance other decision criteria.

Habib, E. and Reed, D., 2013. Parametric uncertainty analysis of predictive models in Louisiana's 2012 Coastal Master Plan.

This study presents an assessment of uncertainty associated with the predictive models utilized in Louisiana's 2012 Coastal Master Plan. In this context, model uncertainty was defined as the deviation of model prediction from the actual ecosystem response to certain proposed projects. The focus is on parametric-related uncertainties, which are due to imperfect knowledge about parameters and relationships used within the models. Due to the large number of models used in the master plan, a reduced set of model parameters (34) was identified as the most uncertain. A limited sampling experiment was designed on the basis of stratified sampling from predefined simple probability distributions of the selected parameters. Two phases of analysis were conducted. The first phase focused on examining the impact of parameter uncertainties on model predictions and comparing such uncertainties with the predicted impacts of individual projects. The second phase focused on comparing model uncertainties in predicting the future-without-action conditions vs. a proposed draft version of the master plan. The study attempts to answer some key questions that are relevant for model development and planning and project selection aspects: How uncertain are the models in predicting changes in key ecosystem metrics? Does the uncertainty vary spatially across the coast and temporally into future years? How does parameter-induced uncertainties compare with those due to other exogenous large-scale drivers? How can the uncertainty analysis inform decisions? Finally, the paper discusses implications of uncertainties for using the models as prediction tools, and highlights critical data gaps and modeling development efforts needed for future analysis.

Groves, D.G. and Sharon, C., 2013. Planning tool to support planning the future of coastal Louisiana.

Coastal Louisiana's built and natural environment faces risks from catastrophic tropical storms. Concurrently, the region is experiencing a dramatic conversion of coastal land and associated habitats to open water and a loss of important services provided by such ecosystems. Louisiana's Coastal Protection and Restoration Authority (CPRA) engaged in a detailed modeling, simulation, and analysis exercise, the results of which informed Louisiana's 2012 Comprehensive Master Plan for a Sustainable Coast. The Master Plan defines a set of coastal risk-reduction and restoration projects to be implemented in the coming decades to reduce hurricane flood risk to coastal communities and restore the Louisiana coast. Risk-reduction and restoration projects were selected to provide the greatest level of risk-reduction and land-building benefits under a given budget constraint while being consistent with other objectives and principles of the Master Plan. A RAND project team, with the guidance of CPRA and other members of the Master Plan Delivery Team, developed a computer-based decision-support tool, called the CPRA Planning Tool. The Planning Tool provided technical analysis that supported the development of the Master Plan through CPRA and community-based deliberations. This article provides a summary of the Planning Tool and its application in supporting the development of Louisiana's Master Plan.