MODELING COASTAL MARSH STABILITY IN RESPONSE TO SEA-LEVEL RISE - A CASE-STUDY IN COASTAL LOUISIANA, USA

In some regions coastal marsh stability is threatened by high rates of sea level rise. The deltaic plain of the Mississippi River is a natural laboratory for the study of marsh stability under conditions of rising sea level because it has been experiencing high rates of local submergence which cause relatively high rates of apparent sea level rise. We constructed a dynamic simulation model to study the relationship of accretion to three components of relative sea level rise: compaction, eustatic rise and submergence. The model is then used to project marsh stability under various future scenarios of sea level rise as well as enhancement of sediment supplies and marsh accretion. The model was calibrated to a C-14-dated sediment deposit which provides a long-term record of sediment accretion. Results indicate that an equilibrium between relative sea level and accretion rates can be attained, but that in this region of coastal Louisiana only the most optimistic assumptions yield coastal marshes that arc stable in the long term.