Proceedings Of The Marine

SUM 2015

Proceedings magazine is a communication tool for the Coast Guard's Marine Safety & Security Council. Each quarterly magazine focuses on a specific theme of interest to the marine industry.

Issue link:

Contents of this Issue


Page 36 of 70

34 Proceedings Summer 2015 With the bar dynamic under-keel clearance study as a primer, the time may be right for a comprehensive river study that will enable us to more defnitively measure ves- sel motion during transits of the entire Columbia. Benefts include: • safely maximizing vessel draft, • potentially decreasing the carbon footprint per ton of export cargo, • pinpointing the most critically needed dredging areas, • improved ability to time voyages. From an economic perspective, it is important to maxi- mize the tonnage of cargo that each vessel can safely move into and out of the river, as fxed vessel operation costs are spread out over more tons of revenue-generating cargo. Additionally, all other things being equal, a deeper draft vessel is "greener" than the same vessel running at a shal- lower draft, since every additional percent of cargo loaded onboard increases fuel consumption by much less than one percent. 3 Finally, stakeholders are also considering better sensors along the lower Columbia. The PORTS' river gauges upgrade was a frst step. Now, additional upgrades, including poten- tially installing fog sensors closer to the mouth and air gap sensors for more accurate under-bridge clearance data, are being considered, as ways to better inform the mariner. About the author: Mr. Fred Myer is the senior waterways planner for the Port of Portland. Endnotes: 1. See Economic_Study.pdf. 2. Hauke Kite-Powell, "Estimating Economic Benefts from NOAA PORTS Informa- tion: A Case Study of the Columbia River," June 2010. 3. Captain Paul Amos, "COLRIP Connect Oregon IV Program Application for Under Keel Clearance Study," November 2013. Bibliography: Beeman, O. Columbia River Refections: A Memoir by Ogden Beeman, copyright 2011, Port of Portland. Parsons Brinckerhoff Vessel Routing and Stage Analysis, October 2013. Available at Columbia River Pilots (COLRIP). Available at USACE Deep Draft Vessel Costs. Available at box/library.cfm?Option=Listing&Type=EGM&Search=Policy&Sort=Default. COLRIP Connect Oregon IV Program Application for Under Keel Clearance Study. Powell, Dr. K. (2010) Estimating Economic Benefts from NOAA Information: A Case Study of the Columbia River. Woods Hole Oceanographic Institute Marine Policy Center Report. Available at Columbia_River_PORTS_Economic_Study.pdf. Burnette, E. "CRD" / Zero Gauge background information. Oregon Board of Maritime Pilots. The TV32 system integrates with U.S. Army Corp of Engi- neers channel surveys to show the most recent depth infor- mation. Along with this bathymetric information, covering the 100-plus mile length of the Columbia River, the system also integrates NOAA charts, the NOAA PORTS river level sensors (the same ones used in LOADMAX), and Google Earth information. Vessel Squat Looking forward, the Columbia River's many stakeholders continue to strive for better navigation through improve- ments. Since the frst days of steam power, it has been under- stood that, the faster a ship goes, the more it tends to sink; this is known as vessel "squat." The problem is that while squat is well understood for vessels operating in deep ocean waters, it is surprisingly poorly understood for vessels oper- ating in shallow, constrained, or confned channels. In part, this is because precise measurement of vessel motion at this level had not been possible until the advent of GPS. For decades vessels have operated along the Columbia River with an excellent safety record, but without a comprehensive understanding of vessel squat in shallow water. This ambi- guity, although successfully managed in the past through caution and prudence, came without the beneft of rigorous empirical data. Compounding the confusion, vessel squat can vary greatly from vessel to vessel and river to river. For example, the same vessel may squat very differently in a shallow channel bordered by steep walls, as opposed to a similar shallow channel bordered by wide, fat, shallow areas. Both of these are present on the Columbia River. Under-Keel Clearance Study A river bar dynamic under-keel clearance study found, not surprisingly, that under-keel clearance needs to be care- fully managed on the bar. While researchers weren't able to establish clear "rules of thumb," they did develop a pro- gram to help determine squat, based on varying conditions, including: • ship's particulars, • loading and stability parameters, • speed, • LOADMAX input, • weather and seas. In general, wave response of vessels crossing the bar is the greatest contributor to risky and hazardous transits. Shorter and slightly shallower vessels tended to resonate more with prevailing swells; in other words, larger vessels did not nec- essarily present the greatest risk.

Articles in this issue

Links on this page

Archives of this issue

view archives of Proceedings Of The Marine - SUM 2015