International Journal

on Marine Navigation

and Safety of Sea Transportation

Volume 3

Number 4

December 2009

381

1 INTRODUCTION

Process of ships movement in water area should be

safely. Its estimation is executed by means of no-

tions of safety navigation. It may be qualified (Galor

W. 2001) as set of states of technical, organizational,

operating and exploitation conditions and set of rec-

ommendations, rules and procedures, which when

used and during leaderships of ship navigation min-

imize possibility of events, whose consequence may

be loss of life or health, material losses in conse-

quence of damages, or losses of ship, load, port

structures or pollution of environment. Very often,

the sea-river ships move on waterways (natural and

artificial) inside of land for hundreds kilometres.

The manoeuvring of ships on each water area is

connected with the risk of accident, which is un-

wanted event in results of this can appear the losses.

There is mainly caused by unwitting contact of ships

hull with other objects being on this water area. The

safety of ship’s movement can be identified as ad-

missible risk, which in turn can be determined as:

adm

=P C

min

(1)

where: R

adm

= admissible risk, P

= probability of

accident and C

min

= acceptable losses level.

As a result, a navigational accident may occur as

an unwanted event, ending in negative outcome,

such as:

− loss of human life or health,

− loss or damage of the ship and cargo,

− environment pollution,

− damage of port’s structure;

− loss of potential profits due to the port blockage

or its parts,

− coast of salvage operation,

− other losses.

The inland waterways are restricted areas those

where ship motion is limited by area and ships traf-

fic parameters. Restricted areas can be said to have

the following features:

− restriction of at least one of the three dimensions

characterizing the distance from the ship to other

objects (depth, width and length of the area),

− restricted ship manoeuvring,

− the ship has no choice of a waterway,

− necessity of complying with safety regulations

− set for local conditions and other regulations.

In a few cases, especially for ports situated inside

of land, there are the waterways and canals with

great lengths of hundreds kilometres. Thus the navi-

gation on such waterways is different than on ap-

proaching waterways and coastal water areas. The

realization of navigation on limited water areas is

consisted on (Galor W. 2005):

− planning of safety manoeuvre,

− ship’s positioning with required accuracy on giv-

en area,

− steering of craft to obtain the safety planned of

manoeuvre,

− avoiding of collision with other ships.

Approach channels to port and port water area are

characterised by occurrence of port structures. These

constructions are result of activity of man and em-

brace aquatic or under-water structure which togeth-

er with installations, builder’s devices connected

The Criterion of Safety Navigation Assessment

in Sea-River Shipping

W. Galor

Maritime University of Szczecin, Szczecin, Poland

ABSTRACT: Sea–river ships can connect the area inside of land with oversea places without of indirect

trans- shipment. In many cases the sea-river ships move on waterways (natural and artificial) inside of land

for hundreds kilometres. Navigation in inland waters has to meet the same requirements as those for pilot nav-

igation. This is due to the relations between the ship size and other objects on water area. These ones caused

the navigation more hard then on open seas. The paper presents the criterion of safety assessment of naviga-

tion during sea-river ships manoeuvring ship in inland waters.

382

with them and other advisable necessary equipment

to realize of its intended function to state whole of

technical using. From sight of view limitation of

movement in water area, ports structures envelop

following component:

− objects arising in result of executing of dredged

works such port and shipyard water, especially

and basin, sea and lagoon fairways, approach

channels, turning basins,

− channels,

− wharfs determining of water area coast and large-

ly making possible berthing to them and mooring

of ships,

− constructions of coast protection such breakwa-

ters, under-water thresholds, strengthening of bot-

tom, scarp of fairways deepened,

− constructions of fixed navigational marks such

lighthouses, situated on shore of sea water area

and aquatic, light lines and navigational marks,

navigational dolphins,

− locks (fig.1),

Figure 1. The lock in Czyżykówko on Wisła – Odra waterway

− structures situated in area of sea harbour, in par-

ticular isles of berthing and trans-shipment, ship-

ping foot-bridges,

− port structures, situated in area of sea harbour in

particular breakwaters, breakers of waves, wharfs

trans-shipment and berthing and other,

− structures connected with communication, in par-

ticular road – bridges, railway, submarine tunnels,

− structures connected with exploitation of sea bot-

tom (drilling towers, platforms, submarine pipe-

lines).

Besides to number to them it is necessary: con-

structions of floating navigational marks, in particu-

lar anchored navigational buoys.

2 THE CRITERION OF SHIPS SAFETY

ASSESSMENT

The restricted area is characterized by a great num-

ber of factors being present at the some time. It

caused that possibility of navigational accident in

these areas is more then in other ones. It means the

navigation safety is lower in restricted areas. The as-

sessing of navigation safety requires the application

of proper criteria, measures and factors. The criteria

make it possible to estimate the probability of navi-

gational accident for certain conditions. The ship

during process of navigation has to implement the

following safety shipping conditions:

− keeping the under keel clearance,

− keeping the proper distance to navigational ob-

struction,

− keeping the proper air drought,

− avoid of collision with other floating craft,

To determine and analyse the safety, especially in

the quantitative manes, the necessary to select values

that can by treaded as a safety measures. It permits

to determine the safety level by admissible risk

(Galor W. 2001a):

= P

[ d(t)

max

< d

min

(0< t <T

)] for c <C

(2)

where: d(t)

max

= distance of craft hull to other ob-

jects during manoeuvring, d

min

= least admissible

distance of craft hull to other objects, T

= time of

ships manoeuvring, c = losses as result of collision

with object and C

min

= the acceptable level of losses.

Because the losses can be result different events,

the following criterion of safety assessment will be

used:

1 Safety under keel clearance (SUKC)

2 Safety distance to structure (SDS)

3 Safety distance of approach (SDA)

4 Safety air drought (SAD)

Thus, there are many categories of risk due to

ship movement in water area. In each case the acci-

dent rate (probability) is determined for each of the

accident categories. The overall risk of ship move-

ment in water area in then the sum of these single,

independents risks:

= R

+ R

(3)

where: R

o =.

overall risk of ship movement in water

area, R

g =

risk of grounding, R

n =

risk of collision

with navigations obstructers, R

c =

risk of collision

with other ships and R

ad =

risk of impact the object

over the ship.

3 SAFETY UNDER KEEL CLEARANCE

(SUKC)

The underkeel clearance is a vertical distance be-

tween the deepest underwater point of the ship’s hull

and the water area bottom or ground. That clearance

should be sufficient to allow ship’s floatability in

most unfavourable hydrological and meteorological

conditions. Consequently:

383

≥

T + R

(4)

where: H – depth, T – ship’s draft and R

–

safe underkeel clearance (UKC).

The safe underkeel clearance should enable the

ship to manoeuvre within an area so that no damage

to the hull occurs that might happen due to the hull

impact on the ground. A risk of an accident exists

when the under keel clearance is insufficient. When

determining the optimized UKC we have to recon-

cile contradictory interests of maritime administra-

tion and port authorities. The former is responsible

for the safety of navigation, so it wants UKC to be

as large as possible. The latter, wishes to handle

ships as large as possible, therefore they prefer to

accept ships drawing to the maximum, in other

words, with the minimized UKC. The maximum

UKC requirement entails restricted use of the ca-

pacity of some ships, which is ineffective in terms of

costs for ports and ship operators. In the extreme

cases, certain ships will resign from the services of a

given port. Therefore, the UKC optimization in

some ports will be of advantage. It is possible if the

right methods are applied. Their analysis leads to a

conclusion that the best applicable methods for UKC

optimization are the coefficient method and the

method of components sum.

In the coefficient method one has to define the

value R

min

as part of the ship’s draft:

min

= η T

(5)

where: η = coefficient and T

c =

deepest draft of the

hull. The applied coefficient η values range from

0.04 to 0.4 (Mazurkiewicz B. 2008). The other

method consists in the determination of R

min

as the

algebraic sum of component reserves [6] which ac-

counts for errors of each component determination:

min

= ∑ R

+ δ

(6)

where: R

i =

depth component reserves and δ

= sum

of errors of components determination.

The UKC is assumed to have the static and dy-

namic component. This is due to the dynamic

changes of particular reserves. The static component

encompasses corrections that change little in time.

This refers to a ship lying in calm waters, not pro-

ceeding. The dynamic component includes the re-

serve for ship’s squatting in motion and the wave

impact. One should emphasize that with this division

the dynamic component should also account for the

reserve for ship’s heel while altering course (turn-

ing).

4 SAFETY DISTANCE TO STRUCTURE (SDS)

The accessible port water area (for given depth) war-

rants safety manoeuvring for fulfill condition:

∈

Ω

(7)

where:

= requisite area of ship’s manoeuvring and

Ω

= accessible water area.

Ships contact with structure can be intentional or

not. Intentional contact steps out when ship berthing

to wharf. During this contact energy dependent from

virtual ship masses and its perpendicular component

speed to the wharf is emitted. In result of ship pres-

sure on wharf comes into being reaction force. Both

emitted energy during berthing and bulk reaction

force cannot exceed admissible value, definite by re-

liability of ship and wharfs. These values can be de-

creased by means of fenders, being usually of wharf

equipment. Ship should manoeuvre in such kind to

not exceed of admissible energy of fender-structure

system. Unintentional contact can cause navigational

accident. Process of ship movement in limited water

area relies by suitable manoeuvring. During of ship

manoeuvring it can happen the navigational acci-

dent. Same events can occur strike in structures,

when depth of water area is greater than draught

ship. There are usually structures like wharf, break-

water, etc., and also floated objects moored to struc-

ture.

5 SAFETY DISTANCE OF APPROACH (SDA)

Where:

The fundamental measure of ships passing is dis-

tance to closest point of approach (DCPA). Its value

should be safety, it means:

DCPA .≥ .DCPA

min

(8)

where: DCPA = distance to closest point of ap-

proach and DCPA

min =

acceptable distance to closest

point of approach.

The accident can happen; when above condition

will not be performance. Knowing the number of en-

tries of ships in a year (annual intensity of traffic),

one can determine the probability of ships collision

for one ship transit:

tIp

⋅= /

(9)

where: p

probability of ships collision in one

transit,

= accident frequency, I

= annual traffic in-

tensity and t = given period.

Determinate the probability of accident for given

number of ship transits it can used the following

formula (Galor W. 2004):

A(N)

= N · p

= I · T · p

(10)

where: P

A(N

) = probability of accident for given ship

transit number and N = number ship of transits.

This relationship is linear because implies propor-

tional growth of probability to considered of ship

384

number transit. More adequate manner is use the sta-

tistical models described the accident probability.

Because accidents are infrequent events thus it can

be used recurrent models. One of them is geomet-

rical distribution:

A(N)

= 1 - (1 - p

)

(11)

Figure 2 presents the probability of navigation

accident for linear and geometrical distributions in

function of ships transit numbers.

Figure 2. Probability of accident in function of transits number

for linear and geometrical distributions

It results that for given value of accident proba-

bility (for example 0.95) for linear distribution it is

achieved up to about three times less than for geo-

metrical distribution.

6 SAFETY AIR DROUGHT (SAD)

Air drought is distance over ship, when manoeuvre

under construction. They mainly consist:

− bridges (road, railway) over waterway (fig.3),

− high voltage lines,

− pipelines over waterway,

The condition of safety ship movement is follow-

ing:

< H

(12)

where: H

=the height of highest point of ship and

= the height of lowest point of construction over

waterway.

In many cases, the sea-river ship’s superstructure

is regulated. It permits to decrease of ships height.

Also other elements of ship’s construction can be

disassembled – for instance masts of radar antenna,

radio etc.

Figure 3. The road bridge over Noteć river in Santok (Poland)-

(Nadolny G. 2005)

7 CONCLUSION

The sea-river ships move on waterways (natural and

artificial) inside of land in many cases for hundreds

kilometres. The ship can pass natural objects (coast,

water bottom) and artificial objects (water port struc-

tures-locks, bridges etc.). Also many other ships can

manoeuvre on area. It caused that the navigation in

inland waters is harder than on open seas. The crite-

rions of safety assessment of ship movement need

more precisely of qualify. The risk can be used as

measure of safety. This risk is a sum of independent

components connected with different possibilities of

potential accidents. They are a result of unwanted

contact with objects on inland water area. The pre-

sented above consideration can permit to analysis of

safety sea-river ships in inland shipping.

REFERENCES

Galor W. (2001): The methods of ship are manoeuvring risk

assessment in restricted waters. Proceedings of the 14th In-

ternational Conference on Hydrodynamics in Ship Design,

Szczecin-Międzyzdroje, 27-29 September 2001, pp. 134-

143.

Galor W. (2001a): The management of ship safety in water ar-

ea. Proceedings of the Marine Technology IV, Editors CA

Brebbia, WIT Press Computational Mechanics Publica-

tions, Southampton, Boston, 2001, pp. 13-20.

Galor W. (2004):Kryteria bezpieczeństwa ruchu statku po

akwenie portowym, Zeszyty Naukowe Akademii Morskie w

Szczecinie nr 3(75), Szczecin, 2004. str. 41-52.

Galor W. (2005): Analiza określania zapasu wody pod stępką.

Materiały XI Międzynarodowej Konferencji Nauk. –

Technicznej „Inżynieria Ruchu Morskiego”, Szczecin.

Galor W. (2006): The ship’s dynamic under keel clearance as

an element of port safety management. Confer. Proc. The

International Conference on Safety and Reliability

(Vol.I), Kraków.

Mazurkiewicz B. (2008):

Sea structures. A guide to design.

Edit by ARCELOR, Gdańsk 2006 (in Polish).

Nadolny G., Galor A. ( 2005): Analiza nawigacyjno- eksploat-

acyjna możliwości ruchu jednostek śródlądowych na szlaku

wodnym Wisła-Odra, Materiały II Konferencji Naukowej

INLAND SHIPPING. Szczecin.