ACCESS NUMBER: M15AC00013

1

STUDY TITLE: Economic and Geomorphic Comparison of OCS Sand and Nearshore Sand for Coastal Restoration 

Projects

REPORT TITLE: Economic and geomorphic comparison of ocs sand and nearshore sand for coastal restoration 

projects 

CONTRACT NUMBER: M15AC00013

SPONSORING OCS REGION: Gulf of Mexico

APPLICABLE PLANNING AREA(S): Gulf of Mexico OCS Region 

FISCAL YEAR(S) OF PROJECT FUNDING: 2016–2019

COMPLETION DATE OF REPORT: 31 Aug 2019

COSTS: FY 16: $108,833; FY17: $185,157; FY 18: $128,482; FY 19: NCE

CUMULATIVE PROJECT COST: $422,472

PROJECT MANAGER(S):Rex Caffey 

AFFILIATION of project manager: Louisiana State University, Coastal Marine Institute

ADDRESS: Baton Rouge, Louisiana

PRINCIPAL INVESTIGATOR(S)*

: Rex Caffey, Daniel Petrolia, Ioannis Georgiou, Michael Miner

KEY WORDS: Sand, Dredging, Barrier Island, Geomorphology, Economics, OCS, Gulf of Mexico, Beach 

nourishment, Coastal restoration 

BRIEF ABSTRACT: The goal of this project was to develop a coupled, geomorphic and economic framework for the 

assessment of nearshore (NS) and Outer Continental Shelf (OCS) sediment in dedicated dredging projects in coastal 

Louisiana. Results indicate that the higher cost of sediment transport for OCS-sourced projects can be offset in 

certain cases by the reduced handling losses and increased resilience of larger diameter sands.

BACKGROUND: Demand for dedicated dredging in US waters has more than doubled in the past decade, with 

particular growth in coastal Louisiana, where an estimated 90 million yd3 of sediment will be needed for barrier 

shoreline and wetland restoration over the next 50 years. Sediment acquisition for these projects is typically restricted 

to two primary sources: near shore (NS) materials of limited quantity and quality, and OCS inputs of potentially higher 

quality and costs. Economic trade-offs between these source types have yet to be systematically analyzed but are

expected to be project- and location-specific; and influenced by a wide range of constraints. In October 2015, BOEM 

initiated a three-year cooperative agreement with Coastal Marine Institute for a study to characterize these 

constraints and integrate them into a comparative, geo-economic framework useful for estimating the costs incurred, 

and the ecosystem services derived, from projects relying on these two source materials. This study involved 

developing and coupling geomorphic and economic sub models into a decision support framework to assess a wide 

range of economic trade-offs related to sediment characteristics, technological limitations, sediment transport 

distance, project scale (spatial and temporal) seasonal risks, and environmental policy.

OBJECTIVES: Construct a geomorphic sub-model of sediment transport for a proxy barrier template and simulate 

nearshore- and OCS-sourced sand transport under a range of project scenarios. Construct an economic sub-model 

for assessing project costs related to harvest, transport and deposition of nearshore- and OCS-sourced sediment 

under a range of project scenarios. Integrate the geomorphic and economic sub-models within coupled frameworks 

for evaluating the benefits and costs of dedicated dredging projects on Louisiana’s coastal barrier islands. Develop 

case studies to examine the economic tradeoffs associated with sediment location, quantity, quality, and 

meteorological forcing over time.

DESCRIPTION: Geomorphic modeling was used to simulate the 50-year trajectory of a proxy barrier island system. 

The Delft3D suite was used to assess cumulative erosion and deposition of sediment, with and without restoration 

project-based nourishments. Data from 93 bids and project reports was used to develop a representative cost model 
ACCESS NUMBER: M15AC00013

2

of dedicated dredging for barrier islands and shorelines. Sub-models were incorporated into an integrated economic 

framework to derive monetized values for ecosystem services as function of simulated benefits and estimated project 

costs over time. Five case scenarios were developed to assess the physical performance of NS- and OCS-sourced 

sediments under various grain sizes and storm conditions at site and system boundaries and for subaerial and 

subaqueous contours. Economic trade-offs were examined for each scenario via break-even value (BEV) calculations 

for various combinations of sediment quality, quantity and transport distance

SIGNIFICANT CONCLUSIONS: The geomorphic and economic conclusion is that grain size matters. Though project 

costs are primarily a function of sediment quantity and distance, project efficiency requires a performance-based 

metric to maximize the return on investment from restoration spending.

STUDY RESULTS Baseline and storm-punctuated trajectories indicated physical advantages in resilience (increased 

volume and area) for larger grain sands (OCS at 160, 165, 200 μm) compared to nearshore sands (156 μm) over a 

50-year project trajectory. Physical resilience translated to economic efficiencies with increases in sand grain size. 

Several OCS-sourced project scenarios were found to have lower BEV (more efficient) than NS-sourced projects with 

shorter transport distances and lower quality sediment.

STUDY PRODUCT(S): Caffey RH, Petrolia D, Georgiou IY, Miner M, Wang H, Kime B. 2019. Economic and 

geomorphic comparison of OCS sand and nearshore sand for coastal restoration projects. New Orleans (LA): US 

Department of the Interior, Bureau of Ocean Energy Management. Contract No.: M15AC00013. Report No.: OCS 

Study BOEM 2020-035. 54 p.

*

P.I.’s affiliation may be different than that listed for Project Manager(s).