Forecasting the Effects of Coastal Protection and Restoration Projects on Wetland Morphology in Coastal Louisiana under Multiple Environmental Uncertainty Scenarios

Abstract

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 km 2 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.

Relationships Between Salinity and Short-Term Soil Carbon Accumulation Rates from Marsh Types Across a Landscape in the Mississippi River Delta

“…For example, increasing salinity can increase the concentration of terminal electron acceptors (such as iron, manganese and sulfate) that can increase microbial mineralization of organic matter and thus could result in a reduction in carbon accumulation (Herbert et al 2015). Therefore, better understanding of how these environmental conditions influence carbon accumulation rates in various coastal wetland types is needed to predict how climate change through sea-level rise and future coastal restoration actions will influence the carbon accumulation rates (Markewich et al 2007;Couvillion et al 2013). In addition, these results may help support wetland restoration and management activities for carbon storage/burial capabilities and carbon credits (McLeod et al 2011;Callaway et al 2012;Hansen and Nestlerode 2014).…”

Identifying the Vulnerabilities of Working Coasts Supporting Critical Energy Infrastructure

“…The implementation of the Louisiana Coastal Master Plan is expected to decrease potential damages from storm surge, and realizing its plans is projected to result in no net loss of land after 20 years and an annual net gain of land after 30 years [29]. This Master Plan includes an array of projects for protecting and restoring the fragile ecosystem through barrier island restoration and sediment diversion, to name a few.…”

LaVegMod v2: Modeling Coastal Vegetation Dynamics in Response to Proposed Coastal Restoration and Protection Projects in Louisiana, USA

“…The hydrology polygons range in size from 0.44 km 2 to 3189 km 2 with a median size of 26 km 2 and the hydrology model predicts two variables used by LAVegMod v2: stage height (water surface elevation relative to mean sea level) and salinity levels (ppt). The soil morphodynamics model divides space into a regular grid of 30 × 30 m cells and LAVegMod v2 uses its classification of each cell as occupied by either land or open water [21]. LAVegMod v2 divides the landscape into 198,169 (500 × 500 m) cells.…”