River forcing at work: ecological modeling of prograding and regressive deltas

Two explicit landscape simulation models were used to investigate habitat shifts in coastal Louisiana due to varying river forcing and sea level rise scenarios. Wetland conversion to open water and yearly shifts of marsh habitats in two contrasting estuarine regions were examined; the Atchafalaya delta which is a prograding delta area with strong riverine input, and the Barataria Basin is a regressive delta with high wetland loss which is isolated from riverine input. The models linked several modules dynamically across spatial and temporal scales. Both models consisted of a vertically integrated hydrodynamic model coupled with process-based biological modules of above and below ground primary productivity and soil dynamics. The models explored future effects of possible sea level rise and river diversion plans for 30 and 70-year projections starting in 1988. Results showed that increased river forcing had large land preservation impacts, and indicated that healthy functioning of the Mississippi Delta depends largely on inputs of freshwater, nutrients, and sediments in river water. These types of models are useful for research and as management tools for predicting the effects of regional impacts on structural landscape level changes.