Storm layer deposition on a coastal louisiana lake bed

Li, H.; Lin, L., and Burks-Copes, K.A., 2013. Modeling of coastal inundation, storm surge, and relative sea-level rise at Naval Station Norfolk, Norfolk, Virginia, U.S.A. Tropical cyclone impacts on wetland, terrestrial, and shelf systems have been previously studied and reasonably delineated, but little is known about the response of coastal lakes to storm events. For the first time tropical cyclone impacts on a shallow coastal lake in the Louisiana coastal plain have been studied using direct lines of evidence. Using side-scan sonar, CHIRP subbottom, and echo sounder bathymetric profiles, the lake bottom and shallow subsurface of Sister Lake was imaged pre- and post-Hurricanes Katrina and Rita to provide a geologic framework for assessing storm effects. Box cores were collected to provide site-specific ground truth data to further evaluate the accretion or erosion of sediment over the short storm period between synoptic geophysical surveys. X-ray radiographs of box cores showed clear increments of recent event sedimentation (1-10 cm in thickness), corroborated with radionuclide dating as being products of the storm period. High percentages of approximately 40% fine sand in the storm layer and its thickness relative to an average long-term sedimentation rate of 2.0 mm/y suggest that transport of storm-related sediments from the inner shelf is a large factor in Sister Lake sedimentation. This study provides a framework and fundamental understanding of lake bottom characteristics and impacts of storm-related physical processes on erosion, sediment resuspension, and deposition. For a general case of subsidence in the Louisiana coastal plain of 6-8 mm/y and future sea-level rise rate of at least 3 mm/y, the sediment deficit for Sister Lake is 7-9 mm/y, which suggests that Sister Lake will deepen and widen with time. © Coastal Education & Research Foundation 2013

Storm induced hydrodynamics and sediment transport in a coastal Louisiana lake

Coupled hydrodynamic modeling and sediment core analysis was used to investigate Hurricane Rita hydrodynamic conditions and associated sediment dynamics in Sister Lake, a shallow coastal lake in Terrebonne Basin, Louisiana. Tropical cyclone impacts on wetland, terrestrial, and shelf systems have been previously studied and reasonably delineated, but little is known about the response of coastal lakes to storm events. This initial investigation of tropical cyclone impacts on a shallow coastal lake clarifies sediment transport and deposition patterns in a geologically complex deltaic region. Modeling results from Hurricane Rita forcing conditions hindcast a maximum storm surge elevation of approximately 1.1m and a significant wave height of 1.0m in Sister Lake. Bed shear stresses across almost the entire model domain leading up to Hurricane Rita\u27s landfall were above the critical value causing erosion of fine-grained bottom sediments, and quickly decreased in the western portion during Rita\u27s landfall, indicating significant deposition in this western portion of the lake. The ideal event sedimentation unit that would result from the storm conditions hindcast from the numerical model was corroborated with stratigraphy identified in box cores; sedimentary units with an erosional base overlain by recently deposited silty material topped by clays. This study provides a fundamental understanding of lake bottom characteristics and impacts of storm-related physical processes on erosion and deposition

A review of sediment diversion in the Mississippi River Deltaic Plain

© 2019 Elsevier Ltd One of the proposed methods for restoring the disappearing Mississippi Delta is sediment diversion which uses channels and structures to divert water and sediment from the Mississippi and Atchafalaya Rivers into adjacent basins. This study presents a comprehensive review of geological and physical aspects of sediment dynamics in the Mississippi River Deltaic Plain (MRDP), with special reference to diversion studies over the past two decades. We synthesize these studies, present the current understanding of sediment diversions in the context of sediment dynamics, identify multiple key knowledge gaps, and make recommendations for future studies. To maximize net land building in the MRDP, management strategies should be focused on (a) enhancing river sediment delivery (both mud and sand), (b) increasing sediment retention in receiving basins and (c) minimizing erosion in bays and estuaries. Compared with extensive studies of land building, there have been relatively fewer studies of erosional processes. A heterogeneous coastal geological framework, cohesive sediment erodibility and subsidence together play complicated yet critical roles in future sediment dynamics in bays and estuaries of the MRDP. Sediment retention rates are highly sensitive to spatial and temporal scales, types of sediments and delivery season. Sediment diversions to seaward receiving basins provide more surge protection but tend to have lower sediment retention due to active coastal processes. Structures and devices that improve sediment retention, trap sediments, dissipate waves, and build living shorelines should be explored and cost-to-benefit analysis is needed. Long-term planning should consider more landward diversions, strategic community relocation, and nonlinear response of the complex sedimentary system of the MRDP

Perspectives on the Restoration of the Mississippi DeltaThe Once and Future Delta /

XX, 194 p. 88 illus., 51 illus. in color.online r

A Review of How Uncertainties in Management Decisions Are Addressed in Coastal Louisiana Restoration

Louisiana has lost over 4800 km2 of coastal land since 1932, and a large-scale effort to restore coastal Louisiana is underway, guided by Louisiana’s Comprehensive Master Plan for a Sustainable Coast. This paper reviews science-based planning processes to address uncertainties in management decisions, and determine the most effective combination of restoration and flood risk reduction projects to reduce land loss, maintain and restore coastal environments, and sustain communities. The large-scale effort to restore coastal Louisiana is made more challenging by uncertainties in sediment in the Mississippi River, rising sea levels, subsidence, storms, oil and gas activities, flood-control levees, and navigation infrastructure. To inform decision making, CPRA uses structured approaches to incorporate science at all stages of restoration project planning and implementation to: (1) identify alternative management actions, (2) select the management action based on the best available science, and (3) assess performance of the implemented management decisions. Applied science and synthesis initiatives are critical for solving scientific and technical uncertainties in the successive stages of program and project management, from planning, implementation, operations, to monitoring and assessment. The processes developed and lessons learned from planning and implementing restoration in coastal Louisiana are relevant to other vulnerable coastal regions around the globe