Kenneth Ned Mitchell

Selection of Dredging Projects for Maximizing Waterway System Performance

Budget allocation to annual maintenance dredging projects conducted by the U.S. Army Corps of Engineers is addressed. Of the many projects requested, only a subset may be selected for funding because of budgetary constraints. The benefits of conducting maintenance dredging at one dredging project depend on other projects in the system that also are being dredged to take advantage of transportation efficiency gains derived from deeper navigable waterways. The proposed integer programming models and heuristic solution algorithms selected dredging projects for funding, while taking into account interdependent benefits. The models considered the waterway network topology, which was derived from flow data of historic waterborne cargo. The solution algorithms ensured efficient computational performance and quality of solutions. The models and algorithms were tested on example port systems from the Great Lakes region, as well as from mainline coastal ports and inland waterways. The models were shown to increase the amounts of system cargo throughput directly supported by dredging relative to traditional rank-order approaches that did not consider project interdependencies. This result was true especially for scenarios in which the overall budget was small relative to the total of all funding requests in question.

Optimal Dredge Fleet Scheduling Within Environmental Work Windows

The U.S. Army Corps of Engineers oversees dredging in hundreds of navigation projects annually, through its fleet of government equipment and through individual contracts with private industry. The research presented here sought to examine the decision to allocate dredge resources to projects systemwide under necessary constraints. These constraints included environmental restrictions on when dredging could take place in response to the migration patterns of turtles, birds, fish, and other wildlife; dredge equipment resource availability; and varying equipment productivity rates that affected project completion times. The paper discusses problem definition and model formulation of optimal dredge fleet scheduling within environmental work windows. In addition, a sensitivity analysis was conducted to provide decision makers with quantitative insights into dredging program efficiency gains that could be realized systemwide if environmental restrictions were relaxed. Opportunities exist to provide decision makers with quantitative insights into how efficiencies might be obtained if targeted research were to show that particular restricted periods could be relaxed without adverse consequences to sensitive and endangered species.

Waterway Performance Monitoring with Automatic Identification System Data

Fiscal constraints at the federal level drive the need for more robust and objective performance evaluation methodologies for use by the U.S. Army Corps of Engineers as it carries out its civil works mission in support of the nations water resources infrastructure. One specific area of need concerns functional performance evaluation of dredged navigation channels at the local level as well as performance evaluation of systems of navigation projects. The nationwide automatic identification system (NAIS) for vessels that operate in coastal waters was instituted after the terrorist attacks of September 2001 and is maintained by the U.S. Coast Guard. The system constitutes an enabling technology to provide the data required for quantitative performance assessments of corps-maintained navigation infrastructure. In this paper, several applications are presented of archival NAIS data toward waterway performance evaluation. An assessment and comparison also are presented of several deep-draft coastal ports with respect to the sensitivity of vessel transit timing to tidal elevations. The NAIS data archive is applied toward a point-to-point transit time monitoring strategy at the local and regional levels. The corps confronts an uncertain fiscal outlook and constrained budgets for annual operations and maintenance activities. These metrics, as well as other potential applications of archival NAIS data, can play a valuable role in the provision of objective, quantitative assessments of waterway performance.

AIS History and Future Improvements in Waterway Management

Widespread adoption of a standardized Automatic Identification System (AIS) by navigating vessels is a recent development in the technological landscape of navigation engineering. As this technology nears a decade in commercial use, it is apparent that practical applications exist for this technology beyond those for which it was designed. When viewed as a remote sensing technology, AIS presents a measure of quantified vessel behavior, the scope of which has - until now - been practically unachievable. This paper outlines the context of current efforts by the U.S. Army Corps of Engineers (USACE) to develop applications for use of AIS data in performance-based management of waterway infrastructure. New metrics for use in waterway management decision-making are discussed in the context of system optimization. Comparison between data components available from AIS records and typical study needs are made to establish a case for further exploration and development.

Underkeel Clearance Reliability Model for Dredged Navigation Channels

This paper presents a reliability measure for selecting marine navigation channel maintenance depth. Resource constraints have resulted in dredging requirements outpacing the funds available to the U.S. Army Corps of Engineers to perform navigation channel maintenance dredging, but navigation managers lack a method to objectively select maintenance depth alternatives to authorized project depths. The reliability of a navigation channel can be determined as the probability that a vessels net underkeel clearance is greater than or equal to 0. Net underkeel clearance was hindcast from underkeel clearance contributors that include sailing draft, water level, bathymetric elevation, vessel squat, and wave response. This method was tested in Charleston Harbor, South Carolina, with an authorized depth of 45 ft (13.7 m). The harbor includes two-way container, tanker, roll on–roll off, and passenger traffic with maximum drafts exceeding design depth. Vessel squat in transit is calculated on the basis of vessel speed, obtained from Automatic Identification System (AIS) data and a representative block coefficient based on vessel size and type. This study used archival AIS data, bathymetric surveys, observed water level elevations, and information collected by vessel pilots to calculate net underkeel clearance of vessel transits through each dredged location within the harbor in 2011. It was determined that channel reliability ranged from 98.7% to 100%. Channels with 100% reliability had minimum net underkeel clearance between 1.0 ft (0.3 m) and 8.3 ft (2.5 m). The approach provides a potential method to select maintenance depth alternatives to authorized channel depths that may result in maintenance cost savings that arise from avoided dredging and associated material management costs.

Use of Nationwide Automatic Identification System Data to Quantify Resiliency of Marine Transportation Systems

This paper describes the approach and the results of an ongoing research effort to assess the resilience of port operations following major disasters and other disruptive events. The work presented in this paper used archival data from the U.S. Coast Guard’s nationwide automatic identification system to quantify the state of resiliency of coastal navigation systems. Illustrating the experimental methodology are case study examples that assess the disruptions that resulted from a collision in March 2014 in the Houston Ship Channel, Texas, and from Superstorm Sandy in 2012 on the greater Port of New York and New Jersey. The methods and results can be adapted and implemented for quantitatively evaluating levels of port activity following disruptive events and for a better understanding of the factors that lead to more resilient maritime systems.

Developing and Implementing a Port Fluidity Performance Measurement Methodology using Automatic Identification System Data

The U.S. Army Corps of Engineers (USACE) is responsible for the maintenance of federally authorized navigation channels and associated infrastructure. As such, USACE requires objective performance measures for determining the level of service being provided by the hundreds of maintained navigation projects nationwide. To this end, the U.S. Army Engineer Research and Development Center partnered with Texas A&M Transportation Institute to develop a freight fluidity assessment framework for coastal ports. The goal was to use archival automatic identification system (AIS) data to develop and demonstrate how ports can be objectively compared in relation to fluidity, or the turnaround time reliability of oceangoing vessels. The framework allows USACE to evaluate maintained navigation project conditions alongside port system performance indices, thereby providing insight into questions of required maintained channel dimensions. The freight fluidity concept focuses on supply chain performance measures such as travel time reliability and end-to-end shipping costs. Although there are numerous research efforts underway to implement freight fluidity, this is the first known application to U.S. ports. This paper covers AIS data inputs, quality control, and performance measures development, and also provides a demonstration application of the methodology at the Port of Mobile, Alabama, highlighting travel time and travel time reliability operating statistics for the overall port area. This work provides foundational knowledge to practitioners and port stakeholders looking to improve supply chain performance and is also valuable for researchers interested in the development and application of multimodal freight fluidity performance measures.