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Proceedings Summer 2015
www.uscg.mil/proceedings
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 http://tidesandcurrents.noaa.gov/publications/Columbia_River_PORTS_
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
http://ascelibrary.org/doi/abs/10.1061/9780784413067.046.
Columbia River Pilots (COLRIP). Available at http://colrip.com/.
USACE Deep Draft Vessel Costs. Available at http://planning.usace.army.mil/tool-
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 http://tidesandcurrents.noaa.gov/publications/
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.