MODERN UNDER-KEEL CLEARANCE MANAGEMENT

This paper provides an overview of recent technological developments t hat have improved the ability to manage under-keel clearance (UKC) in ports. The inaccurate determination of the UKC of large-draft ships en tering or leaving depth-limited ports can have serious safety, economi c, and environmental consequences. A ship's master can manage his ship 's UKC by: (I) taking actions that affect the ship's dynamic draft (su ch as changing the ship's speed) and (2) scheduling his ship's transit of the planned route to ensure that there will be sufficient water le vel for safe passage when the ship reaches locations with controlling depths. To do this, however, he must have accurate real-time and forec ast environmental information along his route, as well as a validated method of predicting his ship's motion (and thus dynamic draft) for va rious situations. At a minimum, this information must include accurate charted depths and underwater hazards, water revels, and ship-specifi c channel-specific prediction formulas for dynamic draft (based on shi p speed, static draft, and water depth). The dynamic draft calculation may also require information on currents, water density, and waves, s well, and/or seiching. Recently developed systems that can provide the necessary information for UKC management include. nowcast/forecast oc eanographic model systems (a necessary step beyond real-time oceanogra phic systems); on-the-fly GPS systems to provide accurate ship motion data for calibrating dynamic-draft prediction systems; modern hydrogra phic measurement systems (such as shallow-water multibeam and side-sca n sonar systems); and modern electronic nautical chart systems (and th eir supporting rapid update services). This paper includes discussion of what further improvements to these systems are needed to make effec tive UKC management a reality.