| Summary: | <p>The United States Army Corps of Engineers (USACE) spends approximately $2 billion annually to investigate, construct, and maintain projects in its portfolio of coastal navigation infrastructure. Of that expenditure, approximately $1 billion is spent annually on maintenance dredging to increase the depth of maintained channels. The USACE prioritizes maintenance funding using a variety of metrics reflecting the amount of cargo moving through maintained projects but does not directly consider the reduction in the likelihood for the bottom of a vessel's hull to make contact with the bottom of the channel that results from maintenance dredging investments.</p>
<p>
Net underkeel clearance, which remains between the channel bottom and the vessels keel after considering several important factors that act to increase the necessary keel depth, is used as an indicator of potential reduction of navigation safety. This dissertation presents a model formulated to estimate net underkeel clearance using archival Automatic Identification System (AIS) data and applies it to the federal navigation project in Charleston, South Carolina. Observations from 2011 including
3,961 vessel transits are used to determine the probability that a vessel will have less than 0 feet of net underkeel clearance as it transits from origin to destination. The probability that a vessel had net underkeel clearance greater than or equal to 0 feet was 0.993.</p>
<p>
A Monte-Carlo approach is employed to prioritize reach maintenance improvement order. A value heuristic is used to rank 7,500 dredging alternatives. 159 options were identified that meet an arbitrarily selected minimum reliability of 0.985. Cost reductions associated with options that met the minimum reliability requirement ranged from 7.7% to 42.6% on an annualized basis. Fort Sumter Range, Hog Island Reach, and Wando Lower Reach are identified as the most important reaches to maintain.</p>
<p>
The underkeel clearance reliability model developed in this work provides a more accurate representation of the waterway users ability to safely transit dredged channels with respect to available depth that is currently available to USACE waterway managers. The transit reliability metric developed provides an accurate representation of the benefit obtained from channel dredging investments, and directly relates the benefit to dredging cost. </p>
|
|---|
