Brendan T. Yuill

Understanding Subsidence Processes in Coastal Louisiana

Abstract Very high subsidence rates are routinely documented within the Pontchartrain Basin and coastal Louisiana. Subsidence promotes land loss and degrades the integrity of infrastructure and ecosystem health. Despite its vast impact on the regional landscape, the precise causes of the subsidence are not well understood; contemporary research attributes measurements of subsidence to many different processes. Because individual subsidence studies often focus on a singular subsidence process and use alternative methodologies, results may not be comparable with or complementary to the results of other studies, hindering attempts to synthesize the collective body of research into a comprehensive regional understanding. This article presents a review of contemporary subsidence research to define the most influential processes in coastal Louisiana. The processes are grouped into six categories: tectonics, Holocene sediment compaction, sediment loading, glacial isostatic adjustment, anthropogenic fluid withdrawal, and surface water drainage and management. Each process category is discussed in a uniform context designed to indentify comparable characteristics and the relative spatial and temporal scales in which they occur. Establishing the full range of influential subsidence processes and providing a means of comparison is a first key step in synthesizing a comprehensive understanding of subsidence in coastal Louisiana.

Subsidence in Coastal Louisiana: Understanding Subsidence: Implications for Coastal Restoration and Protection Planning; New Orleans, Louisiana, 13 January 2009

The high rates of subsidence in coastal Louisiana are a well-documented component of regional land loss, ecosystem function deterioration, and coastal engineering failures. For agencies tasked with managing the effects of subsidence, the wide variability of these rates and their sharp spatial gradients pose significant challenges. Further, there is a lack of scientific consensus on what processes are most responsible for the observed subsidence, which creates uncertainty surrounding spatial patterns of subsidence, as well as a lack of consensus on what areas are most susceptible to it–not trivial questions for the resource management community.