ABSTRACT for ASBPA 2015
DEFENDING THE FOOTPRINT OF FREEDOM
SHORELINE PROTECTION ON DIEGO GARCIA
Diego Garcia is the southernmost atoll of the Chagos Archipelago located in British Indian Ocean
Territory and home to the United States Naval Support Facility, one of the most remote US military
installations. Being a low-lying atoll in the approximate center of the Indian Ocean, the island is subject
to many coastal engineering challenges. This presentation will describe these challenges and some of
the techniques used to balance the shoreline protection objectives with responsible beach preservation.
Nearshore reef mining provided a large supply of aggregate for early development of the US Navy
Support Facility in the 1970s. Attempts were made to keep both the offshore and landside portions of
the fringing reef intact. However, the reality is that the effectiveness of the reef as a natural wave
energy dissipator is reduced. The reef mining also introduced a considerable sink into the sensitive
littoral sediment balance. Sediment transported offshore during storms is deposited in the reef cuts and
is hydraulically unable to be transported back onshore during calm waves due to the large beach rock
formation along the shoreline.
Moffatt & Nichol performed an island wide shoreline investigation in 2008 to identify the primary causes
of erosion, sites of most concern (typically ones near mission critical infrastructure) and develop a short
and long term plan for shoreline protection. In addition to several emergency projects to protect
buildings at risk of erosion an island wide monitoring program was established. The monitoring program
has provided invaluable information about the complex and dynamic littoral processes occurring around
the atoll. The ongoing monitoring will be relied upon for evaluating the impacts of a changing global
climate on sea levels and storm patterns affecting Diego Garcia.
The remote location of Diego Garcia and the sensitive eco-system are formidable constraints to classic
shoreline protection strategies such as beach nourishment, sand retention structures and revetments.
Our last 8 years of work on the island have taught us the value in localized flood protection and
managed “relocation” techniques (retreat is not a favorable term among military circles). Integrating
principles of resilience and relocation with the classic shoreline protection strategies will provide a
sustainable coastline for both the military and environment.
Co-authors:
Aaron Holloway, PE (aholloway@moffattnichol.com)
Moffatt & Nichol
3780 Kilroy Airport Way
Long Beach, CA 90806
(562) 451-9551
Aaron Holloway brings 10 years of experience in coastal and water resources engineering with a focus
on design, analysis, modeling and permitting of coastal, riverine, and civil infrastructure projects. This
experience has included design of beach nourishment projects, shore protection infrastructure, sea level
rise vulnerability studies, levees, flood control improvements, and environmental restorations.
Rob Sloop, PE (rsloop@moffattnichol.com)
Moffatt & Nichol
3780 Kilroy Airport Way
Long Beach, CA 90806
(562) 451-9551