Oil Spill Simulation for Analysis of Environmental Mitigation in

Cilacap Coastal Areas

Mauludiyah

and Mukhtasor

Department of Marine Science, Universitas Islam Negeri Sunan Ampel, Jl. A Yani 117, Surabaya, Indonesia

Department of Ocean Engineering, Institut Teknologi Sepuluh Nopember, Surabaya, Indonesia

Keywords: simulation, oil spill, mitigation, Cilacap.

Abstract: The frequency of oil spills in Cilacap coastal area is high enough to cause ecological and economic

consequences. Based on data from various sources, during the period 1989-2015, there were 17 cases of oil

spills occurred in Cilacap coastal area, 12 were due to tanker accidents and 5 cases due to leaked pipes. Oil

spills often result in both environmental damage and social and economic losses. The main objective of this

work is to do simulation of an oil spill in Cilacap area under different environmental conditions to facilitate

the mitigation for oil spill emergencies at sea by local authorities. To estimate the distribution of oil, referring

to the King Fisher case which occurred on 1 April 2000 in Cilacap area, a spill with 2,500 ton of crude oil

was simulated by MoTum from January to December. The model approach was done by taking into account

the effects of wind, tide, bottom friction, and turbulence. The simulation results reveal that the trajectory of

the oil depends on hydrodynamic forces and highly depends on meteorological conditions, such as wind. The

simulation results also show that Teluk Penyu area, the eastern part of Nusakambangan Island, and Donan

River estuary are area with a high probability of pollution. The mitigation associated with accidental spills

can use one or several approaches, i.e., technology, socio-cultural-economic and institutional and stakeholder

approaches.

1 INTRODUCTION

Accidental large oil spills are one of the disasters and

become important problems that occur in marine and

coastal areas. Accumulatively, an oil spill usually has

a huge impact on marine and coastal environment.

This will directly or indirectly affects fisheries

productivity which is very dependent on

environmental quality. The economic losses will be

greater if the oil spills occur in areas that have high

fisheries production, such as Cilacap coastal areas. It

will mainly impact fishermen who depend on marine

and coastal resources.

Based on data compiled from various sources,

during the period of 1989-2015, there were 17 oil spill

cases that occurred in Cilacap coastal areas, with 12

cases were caused by ship accidents and 5 cases were

due to pipe leakage. Some of the oil spills that have

occurred have shown that Cilacap coastal areas are

vulnerable to oil pollution. Moreover, the traffic

intensity of tankers carrying crude oil as well as oil

refinery produced by Pertamina Refinery Unit IV

Cilacap to Tanjung Intan Port is quite high, with an

average of 70 ships per month.

Oil spills that often occur in Cilacap coastal areas

will have an impact on the marine and coastal

resources. In addition, oil spill will also affect the

economic life of the community which depends on

the location around the occurrence of oil spills. The

Ministry of Environment stated that economic losses

due to the King Fisher ship accident in Cilacap coastal

areas in 2000 reached 272 billion rupiah

(Jayawardana, 2006). For this reason, an

environmental mitigation effort is needed related to

the risk of oil spills in the Cilacap coastal area.

In general, environmental mitigation is an effort

to prevent negative impacts that are expected to occur

or have occurred due to the planning of an activity.

Environmental mitigation can also mean efforts to

overcome the negative impacts that arise as a result of

an activity. According to Law of The Republic of

Indonesia Number 24 of 2007, mitigation is defined

as a series of efforts to reduce disaster risk, both

through physical development and awareness and

capacity building to face disaster threats.

Mauludiyah, . and Mukhtasor, .

Oil Spill Simulation for Analysis of Environmental Mitigation in Cilacap Coastal Areas.

DOI: 10.5220/0008905700002481

In Proceedings of the Built Environment, Science and Technology International Conference (BEST ICON 2018), pages 361-366

ISBN: 978-989-758-414-5

361

Mitigation is done to minimize or to reduce the

possible impacts of a disaster. Therefore, mitigation

can reduce and/or eliminate victims and losses that

may arise. Mitigation must be carried out for all types

of disasters, both those included in natural and man-

made disaster, including oil spills.

In order to prevent and mitigate the risk of oil

spills in the Cilacap coastal area, this study aims to

simulate an oil spill under different environmental

conditions that will provide predictive distribution of

oil when spilled in the Cilacap coastal areas. The

results of the analysis are expected to minimize the

impact, both environmental and socio-economic

impact, that will be caused by oil spill.

2 METHODS

2.1 Simulation Model

In order to estimate the distribution of oil spills in

Cilacap coastal areas, MoTuM (Modul Tumpahan

Minyak) developed by Muin was used. This software

is used to simulate hydrodynamics and the movement

of oil spilled in open seas, straits, bays, or estuaries.

The software generates a series of outputs after the

simulation: the hydrodynamic model, the spread of

oil particles and thickness/oil concentration (fates and

trajectory model), the probability of the stochastic

model, and the probability of the location of oil

pollution sources (receptors model).

MoTuM uses the methodology of combining the

Three-Dimensional Model of Non-Orthogonal

Hydrodinamic Curvilinear Coordinat Technique and

the Oil Spill Model. Hydrodynamics model is based

on tides, current and wind databases. This model is

able to simulate the pattern of three-dimensional

ocean currents due to tides, wind, density, and

influence of rivers. Model applications have been

carried out in several locations such as Fundy Bay

(Canada), Narraganset Bay and Savannah River

(United States), and Ajkwa (PT Freeport Indonesia).

2.2 Model Input Parameters

Data input used in the hydrodynamic model is

bathymetric map, tides, wind speed and direction,

eddy viscosity value, and seabed roughness

coefficient. Bathymetry data from the study area were

obtained from the Pushidrosal (Hydrography and

Oceanography Center, Indonesian Navy). Tidal data

used in this study are the tidal constituent at the

Cilacap Tidal Station from Geospatial Information

Agency with Formzahl number 0.3436, which

indicates that mixed tides, prevailing semidiurnal, are

predominant in the Cilacap coastal areas. Wind data,

in the form of direction and speed, used were 2010

wind data that were obtained from Meteorological,

Climatological, and Geophysical Agency.

In this study, it was assumed that eddy viscosity

was considered constant, 1 m2/s and 0.001 m2/s for

horizontal and vertical direction, respectively. This

parameter is not a fluid property but flow property so

that the value is very dependent on the current and

roughness of the seabed (Muin, 2005). The average

value of seabed roughness coefficient, which is

commonly used in the application of marine

hydrodynamic models, ranges from 0.001 to 0.005.

Therefore, the value of 0.002 was adapted in this

study.

Furthermore, the oil spill model requires a series

of parameters of different kind. Some of the spill

parameters required are geographical coordinates of

the spill, type and quantity of the spill. In addition,

environmental parameters are also included, i.e., eddy

diffusivity, temperature of the sea and air, and

sediment concentration.

The location of the oil spill is 109˚02'57.9" and

07˚45'09" in longitude and latitude, respectively,

referring to the location of the King Fisher oil spill

that occurred in the Cilacap coastal area in 2000

(Figure 1). The simulation was done with a volume of

2,500 tonnes of crude oil in 12-month period, from

January to December. The value of 2,500 tonnes was

chosen based on the average volume data of oil spills

that occurred in Indonesia.

Figure 1. The location of the King Fisher spill

In this study, eddy diffusivity value is determined

at 100 m2/s which is the value of the diffusion

coefficient for the open bay (Joseph, et al., 1998 in

Butyliastri, 2009). Sea water temperature in the

simulation was 27˚C (BAPPEDA Cilacap &

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Diponegoro University, 2001). The air right above the

water was assumed to have the same temperature as

the water surface. The sediment concentration in this

study was assumed to be 5 ppm. According to

Hartami (2008), suspended sediments concentration

ranging from 5 to 25 ppm is considered to be good in

marine aquaculture ecosystems and Cilacap coastal

areas were well known for their marine fishery

production.

2.3 Model Evaluation

Before being used to model the distribution of oil

spills in Cilacap coastal areas, the model was first

evaluated with field case. The field case used in this

evaluation is the oil spill data from the MT King

Fisher, which occurred on April 1, 2000 at 16.00 in

Cilacap coastal areas. MT King Fisher, the Maltese-

flagged tanker, ran aground after crashing into the

reefs in 3 and 5 buoys of the Port of Tanjung Intan

Cilacap in the eastern tip of Nusakambangan Island,

Cilacap. The location of the King Fisher oil spills is

given in Figure 2.

The simulation began at 16.00 with a volume of

4000 barrels of crude oil. When the King Fisher oil

spill occurred on April 1, 2000, Meteorological,

Climatological, and Geophysical Agency informed

that the wind blowing from the south with velocity of

10 knots. Figure 2 shows the trajectory of the oil spill

that occurred after 1 hour. The oil spill began to move

northward. This movement was influenced by the

direction of the wind that blew from the south. Figure

3 shows the oil spill has reached the coast after 6

hours and 40 minutes of simulation. After 24 hours,

the area of the oil spill gets larger and the distance of

the oil spill is also further away, as shown in Figure

MoTum simulation results show that the length of

the coastline affected by the oil spill is 9567 m (Figure

4). Meanwhile, the news related to the King Fisher oil

spill informed that the oil spill was spread over 10

kilometers from Area 70 (Cilacap Village), Teluk

Penyu coast, Nusakambangan Fishing Port, to Tegal

Katilayu and Lengkong coast. This result showed a

reasonable agreement between simulation result and

field case.

Figure 2. King Fisher spill position after 1 hour.

Figure 3. King Fisher spill has reached the coast.

Figure 4. King Fisher spill position after 24 hours.

3 APPLICATIONS AND RESULTS

The first objective of this work is to do a series of

simulation of crude oil of Cilacap coastal area, of

which geographical coordinates belong to a latitude

of 07˚45'09" and a longitude of 109˚02'57.9”,

referring to the King Fisher case. Simulations are

done with 2500 tonnes for crude oil. Twelve

simulations were done considering the hypothetical

cases explained above.

As it can be observed, the model shows the most

probable trajectory of the spill depends on the current

and wind pattern as the oceanographic and

meteorological conditions. From the simulation

results, it was found that the contribution of surface

wind to the distribution of oil spills was quite large.

Oil Spill Simulation for Analysis of Environmental Mitigation in Cilacap Coastal Areas

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Consequently, it is possible to know if the spill

reached the coast and, in this case, when and where it

would impact the coast.

Simulation results showed that in January, oil

spills spread to the southeast (Figure 5). In February

and March, oil spills spread eastward (Figures 6 and

7). In April, oil spills spread to the northwest (Figure

8). In May and June, oil spills spread to the west and

the south (Figures 9 and 10). Oil spills spread

westward in July, August, September, and October

(Figures 11-14). Whereas in November and

December, oil spills spread to the southeast (Figures

15 and 16).

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The simulation results also show that the coastal

area of Teluk Penyu, the eastern end of

Nusakambangan Island and the estuary of the Donan

River are the area that have the highest polluted

probability level. In addition, Widarapayung Beach

and Ketapang Indah Beach also have risk of being

contaminated by oil spills. It can be known from

simulation results in the March scenario, as shown in

Figure 7.

These areas have high biodiversity and are tourist

destination in Cilacap Regency so that if the area is

contaminated by oil, the potential for economic losses

will be very high. The areas that have the probability

of oil contamination are shown in Figure 17.

Figure 5 and 6. Simulation results in January and February, respectively.

Figure 7 and 8. Simulation results in March and April, respectively.

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Figure 9 and 10. Simulation results in May and June, respectively.

Figure 11 and 12. Simulation results in July and August, respectively.

Figure 13 and 14. Simulation results in September and October, respectively.

Figure 15 and 16. Simulation results in November and December, respectively.

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Figure 17. The most polluted area: a) The eastern end of

Nusakambangan, b) Teluk Penyu beach area, c) Donan

River estuary, and d) Widarapayung and Ketapang Indah

Beach

The impact of the oil spill on the Donan River

estuary, which is a mudflat with high biodiversity,

will be different from the impact of the oil spill on the

coastal area in Cilacap, which is a sandy coastal plain.

Productive areas, such as estuary areas, when it is

exposed to an oil spill, will experience a long-term

impact. On the other hand, the sandy beach area also

has a high economic value because it is used, among

others, for beach tourism, docks, and building

materials/mineral resources/mining materials. In

addition, sandy beach area is a habitat for various

flora and fauna. Likewise, the clean-up of oil spills in

estuary areas will be different from it is in sandy

coastal plains.

For this reason, in the context of preventing or

reducing the risk of oil spill while minimizing the

impact caused by oil spill, oil spill mitigation can use

one or several approaches, i.e., technology, socio-

economic culture, institutions, and stakeholders.

As an example, in technology approach, one of

the mitigation efforts can be carried out by widening

and dredging the shipping channel periodically to

reduce the potential for the tanker to be docked. In

addition, the application of technological instruments

to this mitigation effort can also take the form of

applying double hull requirements for oil tankers to

minimize the risk of accidental oil spills.

In addition, mitigation through a technology

approach also means using technology to minimize

the impact caused by oil spills. The application of the

right method in tackling oil spills will be very

effective in reducing oil in the environment, be it the

physical method of using a boom, absorbent,

skimmer, use of dispersants (chemical methods),

bioremediation (biological method), or burning. The

method to deal with oil spills can be used in one

method or in a combination of several methods,

according to the location of the incident, the type of

oil spilled, and the volume of oil spills.

4 CONCLUSIONS

The simulation of the oil spills based on the 3D model

of non-orthogonal hydrodynamic curvilinear

coordinate technique and the oil spill model of

Cilacap coastal areas was investigated. It can be

concluded that the Teluk Penyu beach area, the

eastern end of Nusakambangan Island, and the Donan

River estuary under the present study are the areas

with the highest probability of contamination in

regard to oil spills risk. This research finding may be

able to be utilized for preventing and mitigating the

risk of oil spills in Cilacap coastal area.

ACKNOWLEDGEMENTS

The authors would like to thank PERTAMINA

Indonesia Surabaya office for the permission to use

the MoTum software.

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