Maritime transportation, which accounts for about 80% of worldwide trade, is a cost-effective way to move freight, making ports and waterways key infrastructure. Using larger vessels requires deliberate maintenance of navigable depths in channels and harbors to maximize cargo capacity. Maintenance dredging, or removing bottom sediments to maintain navigable depths, is critical and accounts for much of the annual budget. A U.S. import tax, imposed in 1990, to relieve the burden of operations and maintenance costs on the general treasury, remains a contentious trade issue. Traditionally such funding has been allocated based on benefit-to-cost ratios, rather than on improving vessel efficiencies (which are affected by channel depth). As a result, a backlog of dredging projects has caused inefficiencies, delays and lost revenue.  

A new study in the Journal of Waterways, Ports, Coastal, and Ocean Engineering, “Maritime Transport Efficiency to Inform Demand-Driven User Fees for Harbor Infrastructure,” uses maritime transport efficiency to predict opportunity costs associated with reduced draft availability under variable demand and water surface elevations.

The relationship between maintained harbor depth and cost efficiencies, gained by increased ship volumes, results in economic tradeoffs and opportunities for demand-driven user fees. Authors Dennis Sugrue, M.ASCE and Peter Adriaens, M.ASCE hypothesize that maintenance dredging decisions can be improved by applying expected MTE metrics to estimate variations in transportation costs relative to dredging volumes. Learn more about their research in the abstract below, or by reading the full paper in the ASCE Library,


A dredging backlog in American harbors has produced inefficiencies, delays, and lost revenues for waterway-based logistics and trade. Policymakers have called for increased spending to address maintenance concerns that underscores the need to improve the allocation of public funds or innovate on alternative financing mechanisms. The cost of dredging in the United States has increased more than 250% since 1990 which calls into question the sustainability of current practices. Given that the objective of dredging is to facilitate waterways transport, this study investigated the tradeoffs between transportation cost savings and maintenance spending in the Great Lakes. We use Monte Carlo simulations to calculate Maritime Transport Efficiencies (MTE) as mass per time for bulk iron ore vessels, the predominant vessels on the Great Lakes waterway. Transportation costs, assessed over a range of uncertain demand and fuel pricing, are predicted from natural variations in water surface elevation. Estimates of MTE applied to predict transportation costs are useful in determining annual demand levels for dredging when considered in aggregate, suggesting an opportunity for market-driven funding models for harbor maintenance. Cost savings are evident under conditions such as high-water levels or reduced demand. Increased transportation costs, predicted using MTE, are compared to dredging expenditure. Considering dredging and operating costs together reveals total cost savings. This study produces a quantitative understanding of demand-driven harbor needs which may lead to market-based funding decisions.

Read the full paper in the ASCE Library: