Monitoring of the Louisiana Emergency Berm Project
Gordon Thomson, P.E., D.CE.
Andrew Wycklendt, P.E.
Whitney Thompson, P.E.
Coastal Planning & Engineering
A Shaw Group Company
2481 NW Boca Raton Blvd
Boca Raton, FL 33431
Phone (561) 361-3147
Email – Gordon.Thomson@Shawgrp.com
In response to the Deepwater Horizon Oil spill on April 20, 2010, the State of Louisiana
constructed sand berms along several sections of the state’s barrier islands. Constructed reaches
include Shell Island (Reach W8), Pelican Island (Reach W9), Scofield Island (Reach W10), and
Chandeleur Island (Reach E4). The project placed approximately 6,650,000 cubic yards of
material along 16.1 miles of barrier island shoreline. The berms were constructed with a crest
elevation of +6 feet, NAVD and a crest width of 20 feet. This project increased the elevation of
the existing dunes, plugged breaches, and restored a continuous sandy shoreline along the
constructed reaches.
The emergency permit requirements and special conditions required that monitoring surveys be
conducted immediately after construction as well as at 30, 90, 180, and 360 days following
construction. These surveys extend from a location approximately 1,000 feet landward of the
berm to the -20 foot (NAVD) contour seaward of the constructed berm. Survey lines were
spaced roughly 500 feet apart. Approximately 185 profile line miles were surveyed during each
monitoring event.
This is the first time that a complete set of profile data has been collected at such a short time
interval immediately following fill placement along Louisiana’s barrier islands. The monitoring
data was reviewed to describe the performance of the emergency berms and increase the
understanding of coastal processes immediately following fill placement. Initial performance
metrics included shoreline and volumetric changes. It was determined that standard volume
calculation methodologies were inadequate to describe the variety of coastal processes occurring.
Therefore, the measured volume changes were decomposed to better understand post-fill
placement processes and more accurately describe the performance of the constructed berms.
Processes analyzed include settlement, overwash, offshore loss, and longshore transport.
Review of the data shows that construction of the emergency berms lowered longshore transport
rates and improved the stability of the selected islands. The monitoring data also shows that a
significant loss component is due to settlement of the underlying soils. Although not technically
a loss, the overwash rates were determined to be several times larger than longshore transport
rates. This presentation will focus on how the data was analyzed to identify the various coastal
processes and extract data necessary to develop a sediment budget for each reach of the
constructed berm.
Gordon Thomson is a Senior Coastal Engineer and Director at Coastal Planning & Engineering.
He has worked on several barrier island restoration projects including Chaland Headland, East
Grand Terre, West Belle Pass, Chenier Ronquille, and Shell Island. He has a Masters degree in
Coastal Engineering and a Bachelor’s degree in civil engineering, both from Queen’s University
at Kingston, Canada. He is licensed as a professional engineer in Florida, Louisiana,
Massachusetts, North Carolina, and Mississippi.