● Research Trends and Results

Proposal for Port Entry Operation to Increase Port
Entry Draft of Bulk CarriersPort Planning Division Port and Harbor Department
AKAKURA Yasuhiro, Head of Division (Dr.Eng.)(Keywords) Tidal level, UKC, fairway depth, maximum draft, J-Fairway
1. Current status of tidal level use
Bulk carriers and other large vessels normally use
tidal levels when entering and leaving ports. Thismethod means waiting for tides, but enables vessels
to enter and leave port with a larger draft. Fig. 1shows the relationship between fairway depth andmaximum draft; the fairway depth added to the tidal
level is equal to the maximum draft added to theUKC (Under Keel Clearance). In Australia, USA,Netherlands and other countries, UKC is managed
by consulting weather and sea condition forecasts;
this system makes effective use of tidal levels whenvessels enter and leave port. In Japan, on the other
hand, port entry operation is fixed; UKC is required
to be about 10% of the maximum draft irrespectiveof weather or sea conditions.

3. Confirmation of effectiveness
Table 1 confirms the effectiveness of port entry
operation using J-Fairway, based on the largest classof bulk carrier conceivable under present
circumstances in five ports (selected frominternational bulk strategy ports). Compared toconventional fixed operation, the port entry draft
increased by the “UKC difference”, making it
possible to increase the cargo by about 3% of totalload capacity. When using the same draft but
reducing the tide waiting time, it was confirmed thatthe fairway navigable time was vastly increased.
Using J-Fairway for port entry operation allows
operators to make effective use of existing facilities.
As such, it is hoped that positive changes tooperational standards will be considered in each port.
Table 1. Results of case studies(2 weeks in June 2011)

Tidallevel
潮位Standard
基準水面
water surface
Fairwaydepth
航路水深Maximum

最大喫水draft

港湾Port（cm）

Onahama
小名浜

34

Kashima
鹿島

60

Kisarazu
木更津

55

Nagoya名古屋

37

Shibushi
志布志

35

UKC

Figure 1. Relationship between fairway depth andmaximum draft
2. Port entry operation using J-Fairway
J-Fairway is a program for Class 2 verification offairway dimensions included in the 2007 amendment
to “Technical Standards and Commentaries for Portand Harbour Facilities in Japan”. It can calculate therequired fairway width and depth to suit various
vessel types, weather and sea conditions. Fairway
design is computed using the port entry limits forweather and sea conditions. However, in a normal
navigational environment in calm waters, therequired fairway depth is smaller than the port entry
limit conditions. Thus, if the required UKC whennavigating the fairway can be calculated in advanceby using predictions for waves and tidal level, it will
be possible to navigate with a larger draft without
losing navigational safety. As an alternative option,
the tide waiting time can also be reduced.

UKC
UKC
difference
水深差(cm)

追積可能
航行可能時間率
Navigable time ratio
Increase in(average daily ratio)
cargo
トン数
（日当たり平均時間）
tonnage (MT)（MT）
UKC10% J-Fairway
14.0%
59.8%
2,500(3.4)(14.4)
56.5%
91.4%
9,000(13.6)(21.9)
83.0%
96.1%
11,200(19.9)(23.1)
77.7%
90.5%
2,400(18.6)(21.7)
43.8%
71.4%
2,300(10.5)(17.1)[Reference]
Transport Policy Studies’ Review Vol.15, No. 1NILIM Research Reports No. 47