KUBLA PORTS 2014
TECHNICAL MANUAL
© Kubla Ltd. 2014. All rights reserved
©Kubla Ltd. 2013-2014. All rights reserved
Technical Manual
Kubla Ports 2014
Rev. 00
Dec. 2013
CONTENTS
1
Introduction .................................................................................................................................... 1
2
Co-ordinates and units .................................................................................................................... 2
3
Determination of channel dimensions............................................................................................ 3
Overview ............................................................................................................................................. 3
Design Vessels ..................................................................................................................................... 3
Points along channel ........................................................................................................................... 3
Manual overrides ................................................................................................................................ 3
Order of calculations ........................................................................................................................... 4
4
Bend radii ........................................................................................................................................ 5
5
Determination of channel Bottom Levels ....................................................................................... 6
Overview ............................................................................................................................................. 6
Non-tidal vessels ................................................................................................................................. 6
Tidal vessels ........................................................................................................................................ 6
Final Bottom Levels ............................................................................................................................. 7
6
Determination of channel widths ................................................................................................... 8
Overview ............................................................................................................................................. 8
Determination of parameters ........................................................................................................... 10
Tidal Vessels ...................................................................................................................................... 10
Widths in bends ................................................................................................................................ 11
Final channel widths ......................................................................................................................... 11
7
Determination of dredging quantities .......................................................................................... 12
©Kubla Ltd. 2014
Table of Contents
Technical Manual
Kubla Ports 2014
Rev. 00
Dec. 2013
1 INTRODUCTION
Kubla Ports is software which facilitates the design of Approach Channels, allowing many channel
alignment options to be considered in very little time. Once site data is loaded into the software and
channel alignments are drawn by the user, the software automatically calculates appropriate
channel dimensions (e.g. widths, depths) based on the concept design method described in PIANC’s
guideline ‘Approach Channels - A Guide for Design’ (1997). If necessary, the user can override
automatically calculated dimensions based on their judgement and experience. Whether the
channel dimensions are automatically or manually defined, the software will instantly calculate and
display the dredging quantities.
This Technical Manual describes how Kubla Ports 2014 determines channel dimensions and
calculates dredging quantities. A description of how to use the software is provided separately in
the User Manual, which is available from www.kublasoftware.com.
Important Note:
No software is a substitute for engineering knowledge and judgement. Kubla Ports is designed to
make it easier and quicker for a qualified and experienced professional to develop concept design
options for approach channels. The user is assumed to understand the channel concept design
process described in the PIANC Guidelines. They should also familiarise themselves with how the
software works by reading this Technical Manual, and apply their experience to the design process,
and never blindly accept the designs that the software produces.
©Kubla Ltd. 2014
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Technical Manual
Kubla Ports 2014
Rev. 00
Dec. 2013
2 CO-ORDINATES AND UNITS
Kubla Ports works in Easting and Northing co-ordinates, and with elevations relative to Mean Sea
Level (MSL), all in metres. No other co-ordinate systems or units are currently supported.
If you have data, such as bathymetry or wave heights, in another co-ordinate system it will be
necessary to convert it before you load it into Kubla Ports. Converters are available which enable
different co-ordinate systems to be converted into, for example, the Universal Transverse Mercador
(UTM)system which can be used by Kubla Ports.
©Kubla Ltd. 2014
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Technical Manual
Kubla Ports 2014
Rev. 00
Dec. 2013
3 DETERMINATION OF CHANNEL DIMENSIONS
OVERVIEW
Channel dimensions are determined by Kubla Ports based on the concept design method in the
PIANC Guidelines ‘Approach Channels - A Guide for Design’ (1997). Using these guidelines, and
some necessary assumptions, the minimum channel dimensions are determined for each of the
design vessels and the minimum overall dimensions for the channel are found.
DESIGN VESSELS
The user can specify as many design vessels as they require. If more than one design vessel is
specified then the design process will be repeated for each one in turn and the most critical vessel
will be used to set the channel dimensions. It may be that the channel’s width, for example, is set
based on the requirements of one design vessel and the channel’s depth is set based on another.
The calculations outlined in the following pages are described for a single vessel. If more than one
design vessel is specified then these same calculations will be repeated. If the design vessel has
different properties leaving and returning (e.g. if it’s always unladen leaving the port then it will have
a lower draught) then the calculation will be repeated for each direction of transit.
POINTS ALONG CHANNEL
Since some design parameters (e.g. waves) can vary along the channel, channel dimensions are
determined by checking a series of points along the channel. These points are spaced along the
channel with the following criteria:


Points are not more than 50m apart
In bends, points are not more than 5° apart around the curvature of the bend
The critical point for a particular channel element (i.e. straight section or bend) is found. This is the
point which requires the deepest or widest channel section, and the width and depth for the whole
channel element is set based on this point. While widths and depths cannot vary within a single
channel element, it is possible for the dimensions of channel elements to be different.
MANUAL OVERRIDES
It is possible for the user to manually override dimensions for a channel element, such as the width,
the depth or the radius for bends. In this case Kubla Ports will continue to automatically calculate
the dimensions which have not been overridden. For example, if the user manually overrides the
depth of a channel element, but not the width, then the software will calculate the channel width
using the depth which has been specified manually.
©Kubla Ltd. 2014
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Technical Manual
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Rev. 00
Dec. 2013
ORDER OF CALCULATIONS
Channel dimensions are interrelated. For example, a shallower channel may require additional
width to compensate. A further complication comes from the bend radii, as these affect the location
of the centre line points along the channel which are checked to determine channel widths and
depths. In order to avoid these inter-dependencies, it is necessary to fix the order of calculations
and to make some assumptions in the earlier calculations regarding the later ones. Channel
dimensions are calculated in the order below using the methods described in the following pages.
1. Bend Radii
2. Channel bottom levels
3. Channel widths
©Kubla Ltd. 2014
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Technical Manual
Kubla Ports 2014
Rev. 00
Dec. 2013
4 BEND RADII
Figure 5.8 of the PIANC Guidelines gives a relationship between a vessel’s rudder angle and the ratio
between the bend radius and the ship’s length (R/Lpp), for a number of different depth/draft ratios.
Bend radii are determined by Kubla Ports using this relationship.
Since the bend radii are generally set before the channel depths are known it is necessary to make
an assumption regarding the depth/draft ratio to use to determine the bend radii. For the sake of
simplicity and speed, this is assumed to be at a minimum value of 1.1 for each design vessel. The
following relationship is estimated from Figure 5.8 of the PIANC Guidelines for a vessel with a
depth/draft ratio of 1.1.
25
20
y = 0.0175x2 - 1.245x + 27.1
R/Lpp
15
PIANC data
Data used in Kubla Ports
10
5
0
0
10
20
30
40
Rudder Angle (°)
Any rudder angles greater than 35° use the same ratio as for 35°. Rudder angles below 5° are not
permitted. The ratio obtained following these rules is multiplied by the vessel’s length between
perpendiculars (Lpp) to obtain the bend radius.
©Kubla Ltd. 2014
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Technical Manual
Kubla Ports 2014
Rev. 00
Dec. 2013
5 DETERMINATION OF CHANNEL BOTTOM LEVELS
OVERVIEW
The required channel depths are based on the following simple assumption and the wave heights
that the user has defined.
Wave Height
<0.5m
0.5-1.0m
>1.0m
Min. depth/draft ratio
1.1
1.3
1.5
A check is also made to set the depth in order to limit the vessel’s Froud number to 0.7 using the
following equation.
𝑆𝑝𝑒𝑒𝑑
/9.81
0.7
Min. depth/draft ratio = √
Where the vessel’s speed has been converted into m/s
Therefore the design vessel’s speed can also affect the channel depth in some cases.
NON-TIDAL VESSELS
In the case of non-tidal vessels (where ‘all states of tide’ is selected) the water level is taken from the
minimum water level in the spring and neap time series, and the minimum bottom level is
determined as follows:
Min. bottom level = Min. water level - (Vessel draft x Min. depth/draft ratio)
TIDAL VESSELS
It is possible for the user to specify that a design vessel only needs to be able to transit the channel
at high tides, or even only at high spring tides. If this is specified then the programme will consider
variable water levels as the vessel transits the channel, based on the time-series for the neap tide in
the case or ‘high tide only’ being specified, or the spring tide if ‘high spring tide only’ is selected.
Kubla Ports will consider vessel transits start times every hour from the first tidal record to the last
that will allow the vessel to complete its transit. For each transit time the water level will be
determined at each point as the ship moves along the channel, based on the design vessel’s speed
and the tidal time series. The minimum bottom level will be determined at each point based on
these water levels using the following equation.
©Kubla Ltd. 2014
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Technical Manual
Kubla Ports 2014
Rev. 00
Dec. 2013
Min. bottom level = Water level - (Vessel draft x Min. depth/draft ratio)
Once channel bottom levels are determined for each transit, the ‘cost’ of each transit will be
determined and the cheapest transit will be selected to set the bottom levels. The cost is assessed
by summing the dredging depths at each point along the channel.
Cost = ΣDredging depth
Where Dredging depth = Max(0, Existing level - Min. bottom level)
This is a fast and approximate way to compare prospective dredging volumes for each transit where
the effect of channel width and side slopes is neglected. The transit with the minimum ‘cost’ is used
to set the minimum bottom levels required along the channel for a given design vessel.
FINAL BOTTOM LEVELS
The bottom level for each channel element (straight section or bend) is determined based on the
lowest of each of the points considered along that element. Minimum bottom levels determined in
this way are rounded to the nearest 0.5m before the addition of any allowances for over-dredging
that the user has specified.
Bottom levels will not vary for a single channel element, but they may vary from one channel
element to another. If the channel has a long straight section and a change in depth is required then
this can be achieved by adding a ‘bend’ in the channel, but keeping it in line with the straight
section.
©Kubla Ltd. 2014
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Technical Manual
Kubla Ports 2014
Rev. 00
Dec. 2013
6 DETERMINATION OF CHANNEL WIDTHS
OVERVIEW
Channel widths are set based on the concept design method outlined in the PIANC Guidance and
using the data which the user has input to define the site conditions and also in the properties of
each channel element. The channel width for a given point along the channel is determined using
the following expression for vessels where one-way traffic is specified:
𝑛
𝑤 = 𝑤𝐵𝑀 + ∑ 𝑤𝑖 + 2𝑤𝐵
𝑖=1
…and with the following expression where two-way traffic is specified.
𝑛
𝑤 = 2𝑤𝐵𝑀 + 2 ∑ 𝑤𝑖 + 2𝑤𝐵 + ∑ 𝑤𝑝
𝑖=1
Where 𝑤𝐵𝑀 = basic manoeuvring lane, taken from the user-specified manoeuvrability for the
vessel at the depth in question, using the following table:
Vessel Manoeuvrability
𝑤𝐵𝑀
good
1.3B
moderate
1.5B
poor
1.8B
Where B is the beam of the design vessel
𝑤𝑖 = additional widths, taken from the table on the following page.
𝑤𝐵 = additional width for bank clearance, taken from the table below, with the userspecified bank type for the channel element in question, the vessel speed, and
the specified wave height at the point on the channel.
Vessel
Speed
Sloping channel
edges and
shoals
Steep and hard
embankments,
structures
Fast
Moderate
Slow
Fast
Moderate
Slow
Outer channel exposed
to open water
(WAVE HEIGHT > 1m)
0.7B
0.5B
0.3B
1.3B
1.0B
0.5B
Inner channel protected
water
(WAVE HEIGHT < 1m)
- (0.7B)
0.5B
0.3B
- (1.3B)
1.0B
0.5B
Where fast is > 12 knots, moderate is 8-12knots, and slow is < 8knots
𝑤𝑝 = additional width for passing distance
Vessel speed
(knots)
Encounter
traffic density
©Kubla Ltd. 2014
-
Fast
Moderate
slow
light
moderate
heavy
Outer channel exposed
to open water
(WAVE HEIGHT > 1m)
2.0B
1.6B
1.2B
0.0
0.2B
0.5B
Inner channel
protected water
(WAVE HEIGHT < 1m)
- (1.8B)
1.4B
1.0B
0.0
0.2B
0.4B
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Technical Manual
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Dec. 2013
In order to automate these calculations, some simplifications are made to the PIANC method by
Kubla Ports. These simplifications are shown in red, with the black text being the PIANC Guidance.
The most significant change is that the decision as to whether it is an inner or outer channel is based
only on the wave height, where wave heights < 1m are considered inner channels and others are
outer channels.
Width, wi
Vessel speed
(knots)
Prevailing
cross wind
(knots)
Prevailing
cross current
(knots)
Prevailing
longitudinal
current
(knots)
Significant
wave height
(Hs) and
length (λ)
Aids to
navigation
Depth of
waterway
Cargo hazard
level
Vessel
Speed
-
Fast > 12
Moderate > 8 - 12
Slow 5 - 8
Mild ≤ 15
Moderate 15-33
-
Severe 33-48
-
Negligible < 0.2
Low 0.2-0.5
-
Moderate 0.5-1.5
-
Strong 1.5-2.0
-
Low ≤ 1.5
Moderate 1.5-3
-
Strong > 3
-
Hs ≤ 1 and λ ≤ L (H < 1)
3 > Hs > 1 and λ = L (3 > H > 1)
-
Hs > 3 and λ > L (H > 3)
-
Excellent with shore traffic control
Good
Moderate with infrequent poor visibility
Moderate with frequent poor visibility
≥ 1.5T
1.5T - 1.25T
< 1.25T
Low
Medium
High
All
Fast
Mod
Slow
Fast
Mod
slow
All
Fast
Mod
Slow
Fast
Mod
Slow
Fast
Mod
Slow
All
Fast
Mod
Slow
Fast
Mod
slow
All
Fast
Mod
Slow
Fast
Mod
Slow
Outer Channel exposed
to open water
(WAVE HEIGHT > 1m)
0.1B
0.0
0.0
0.0
0.3B
0.4B
0.5B
0.6B
0.8B
1.0B
0.0
0.1B
0.2B
0.3B
0.5B
0.7B
1.0B
0.7B
1.0B
1.3B
0.0
0.0
0.1B
0.2B
0.1B
0.2B
0.4B
0.0
≈2.0B (2.0B)
≈1.0B (1.0B)
≈0.5B (0.5B)
≈3.0B (3.0B)
≈2.2B (2.2B)
≈1.5B (1.5B)
0.0
0.1B
0.2B
≥0.5B (0.5B)
0.0
0.1B
0.2B
0.0
~0.5B (0.5B)
~1.0B (1.0B)
Inner Channel
Protected Water
(WAVE HEIGHT < 1m)
0.1B
0.0
0.0
0.0
- (0.3B)
0.4B
0.5B
- (0.6B)
0.8B
1.0B
0.0
- (0.0)
0.1B
0.2B
- (0.3B)
0.5B
0.8B
- (0.5B)
- (0.8 B)
- (1.1B)
0.0
- (0.0)
0.1B
0.2B
- (0.1B)
0.2B
0.4B
0.0
(Outer Channel-2.0B)
(Outer Channel-1.0B)
(Outer Channel-0.5B)
(Outer Channel-3.0B)
(Outer Channel-2.2B)
(Outer Channel-1.5B)
0.0
0.1B
0.2B
≥0.5B (0.5B)
≥1.5T
0.0
<1.5T-1.15T
0.2B
<1.15T
0.4B
0.0
~0.4B (0.4B)
~0.8B (0.8B)
Where T = vessel draft and H = wave height
©Kubla Ltd. 2014
Page 9 of 12
Technical Manual
Kubla Ports 2014
Rev. 00
Dec. 2013
DETERMINATION OF PARAMETERS
In order to calculate the channel width with the methods described above the following parameters
are determined for each point along the channel.
1. Cross wind. Taken from the wind climate that the user has defined. The two angles which
are 90° to each side of the channel (i.e. crossing it) are determined, and the wind speed for
these two directions are determined from the wind rose by linear interpolation. The cross
wind is taken to be the largest of the two values.
2. Cross current. Taken from the tidal currents that the user has defined. The current speed
and direction is determined at the time in question by linear interpolation through time
between input tidal records. The cross current is determined from the component of the
current vector which runs perpendicular to the channel element.
3. Longitudinal current. Taken from the tidal currents that the user has defined. The current
speed and direction is determined at the time in question by linear interpolation through
time between input tidal records. The longitudinal current is determined from the
component of the current vector which runs parallel to the channel element.
4. Wave height. Wave height points input by the user are triangulated along with the coastline
and the outline of the bathymetry. Coastline and outline points take the wave height of the
closest wave height point which the user has input. The wave height at the point in question
is determined from this triangulation using bilinear interpolation.
5. Depth of waterway. The depth of the waterway is determined based on the dredged
channel level at the given point and the tidal water level at the given time.
TIDAL VESSELS
In the case of tidal vessels channel width are determined by checking vessel transits at hourly
intervals across the period of tidal records. For every transit time which is viable in terms of the
already-determined channel depths, the required width is determined at each point along the
channel. The transit which requires the lowest average channel width is used to set the widths of
the channel.
If the vessel is to transit at high spring tides then the spring tide is checked only. However, if the
vessel is to transit on any high tide then both spring and neap tides are checked and the one which
necessitates the wider channel is used.
©Kubla Ltd. 2014
Page 10 of 12
Technical Manual
Kubla Ports 2014
Rev. 00
Dec. 2013
WIDTHS IN BENDS
In bends the method outlined for straight sections will be followed for each point in the bend, but
the following additional check will be applied.
Figure 5.9 of the PIANC Guidance gives a relationship between the Rudder Angle and the swept
width in a bend for a number of depth draft ratios, as summarised below. This figure is used to
check the width of the channel in the bend is wide enough. w/B is read from this figure for the 2
depth/draft ratios on either side of the depth/draft ratio of the point in question, and the final value
is obtained by linear interpolation between the two.
Depth/draft
ratio
1.8
1.5
y = -0.0002x2 + 0.031x + 1
1.3
y = -0.0001x2 + 0.0231x + 1.0005
y = -8E-05x2 + 0.0173x + 0.9985
1.4
1.2
1.15
1.3
1.1
y = -5E-05x2 + 0.0115x + 1
1.7
1.6
w/B
1.5
y = -5E-05x2 + 0.0141x + 1.001
1.2
1.1
1
0.9
0.8
0
10
20
30
40
Rudder Angle (°)
FINAL CHANNEL WIDTHS
The width of each channel element (straight section or bend) is determined based on the widest of
each of the points considered along that element. Channel widths determined in this way are
rounded to the nearest 1.0m.
Widths will not vary for a single channel element, but they may vary from one channel element to
another. If the channel has a long straight section and a change in width is required then this can be
achieved by adding a ‘bend’ in the channel, but keeping it in line with the straight section.
If a bend’s width is being automatically calculated, it will be fixed so that it is not less than the widest
of the straight sections on either side of it.
©Kubla Ltd. 2014
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Technical Manual
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Rev. 00
Dec. 2013
7 DETERMINATION OF DREDGING QUANTITIES
Whether channel dimensions are input manually or automatically, dredging quantities will be
automatically calculated and displayed.
This calculation is based upon a Delaunay triangulation of the bathymetry points which the user has
input, and the channel design which has been produced. Side slopes are taken into account when
determining these volumes, based on the slope angles which the user has specified for each channel
element.
©Kubla Ltd. 2014
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