MODELLING OF SYSTEM DYNAMICS ON UPPER COURSE OF
RIVER IN JAVA ISLAND, INDONESIA
Ervan Maksum , Tusy A. Adibroto
Agency for the Assesment and Application of Technology
J. M.H Thamrin 8, New Building 20" floor Jakarta Indonesia
e-mail : ervan @btig.pt-bppt.go.id
The Sustainability of a Watershed ecology depends on numerous factors, especially
land and water availability. Transformation occurring on a watershed can be seen from the
forest openings in the upstream to the conversion of rice fields into settlements and industrial
areas in the downstream. The transformation determines the water cycle of watershed, such
as absorbency, thereby affecting the river's water flow and quality. Mismanagement on the
upstream area, in addition, may affect the downstream area.
This paper is aimed to observe and understand the occurring transformations of
watershed in Java Island - Indonesia. Furthermore, this paper will be related to the
sociological and economical aspects at the community in the river upper course in the north
coast of Java. Thus, it will provide the basic consideration for well-managed watershed by
integrated System Dynamics program applied to support the analysis.
1. INTRODUCTION
Development of downstream watershed of Jakarta north coast is an expansion
of Jakarta area to the north coast direction which includes an area of 87.5 km2. The
development of this area is expected to become a water front city. In addition to
becoming the alternative of settlement which is difficult to be more expanded to other
areas, the development of Jakarta north coast has an additional value, especially for
the office complex and tourism.
The transformation of downstream watershed areas will cause the change of
stability on such areas. With the expanding of coastal surface area, then the condition
of river estuary which initially has the direct contact to the sea is becoming the river
body. Consequently, the area physical condition which is initially fertile for biota
requiring estuary/inlet water as their life media will be shifting, and to return to the
condition at which the biota can live will require a long time.
2. MODEL FRAME
To know the cycle of land surface addition and reduction as well as the
housing availability which is the most potential stimulant of the coastal area
expansion (reclamation), then it is necessary to build the structural relationship
picturing the behaviour of such areas. This behaviour picture is expected to reflect
the logical relationship between the systems visible inside. Hence this model can be
used to determine the coastline structural dynamics (the downstream watershed area).
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Simulation of the downstream watershed area dynamics is built by using a
dynamics method, a model which illustrate the causality relationship of all system
constituting factors as a basis to know and understand the behaviour of system
dynamics.
4.1, GENERAL MODEL FRAME
This model consists of several sub-systems, those are : firstly, land surface;
secondly, investment for reclamation; thirdly, settlement development. On the sub-
system of Jand surface the model will be built by two loops, both are negative loops
(Figure 1). Negative loop is a loop functioning as the controller. The output of this
negative loop is directed to the equilibrium if it is combined with the positive loop |
(ARCHTYPE System, Pegasus 1996). The graphical output from this two negative !
loops are the drifting goals.
Nature
+ > Fluctuation of Lang:
coastal Availability
Lie
(+h)
Land Coastal area | Land use in
available <——— +“— coastal area
| @ ac ® Landot ay eastalatea_+ | Economic
and of tand
I+ ion usal reclamation en aioe
[Constructio for + “
nate o settlement
+ Kick back of Investor
investment of +—— revenue
‘Amount of houses ————» Settiement Mrclernaton
Figure 1. Sub-Model Structure of Land Surface Figure 2. Frame of Investment Sub-Model
Area Structure
The first loop is an availability of land surface which functions as settlement
areas. Firstly, land surface will decrease and increase naturally because of abrasion
and accretion. This cycle is not included in the drifting goals pattern because the
accumulation of land surface transformation caused by this cycle is near zero.
Secondly, land surface will experience a transformation due to human activities as
shown on Figure |. Decreasing land surface area does not mean that the land is used
up, as happening during abrasion. Land surface area is increasing because of
reclamation. Progressively that the reclamation will cause the land surface increasing
which will then increase the land available. Such conditions will then directly
increase the settlement development on such areas by which the number of houses
will also increase. From the existing number of houses, then it will encourage the
desire to expand the settlement area by which the land area will be reduced. The
second loop is land surface area with the land utilisation. The increasing land surface
216
nese
anatase
area will cause the land utilisation also increases, in other hand however, the more
land area utilised then land surface area will be narrower or reduced. Therefore the
system will point to the goal seeking or approach the constrain.
4.1, INVESTMENT SUB-SYSTEM
This investment sub-system is built in two loops (Figure 2), positive loop and
negative loop. The graphical output is fixes that fail. The first loop is an interaction
between investment and land surface area. In this positive loop the increasing land
surface area will cause the increasing of economical land allocation. This increasing
economical land can be done quantitatively or qualitatively. The quantitative
increasing means that the increase automatically happens if the land surface area
increases, while the qualitative increasing of economical land is because the
improvement of human ability with the technology to increase its economical value.
The increasing economical value of a land will then add the investor revenue.
On this land utilisation loop, the wider land utilisation or the wider area
recommended for the reclamation area, then the land surface area will be wider.
Meanwhile, the wider the land surface area then the area of land utilisation will be
more used-up or reduced to near zero. The system analysis stated that this sub-model
interaction pattern is Fixes that files, therefore even though the decision to limit this
area is accomplished, but the main problem that the reclamation rate is increasing will
happen. Furthermore result of behaviour pattern of this model show in the figure 3 &
figure 4, :
—1~Pengurangan_lahan
=z Abrasi_akresi
=3—Penggunaan_Jahan
=p reklamasi
—2~Pengurangan_Jahan
4,980 2,000 2,080 1,960 2,000 2,060
Time Time
7
Figure 3. Influence of Abrasion and Accretion _‘Figure 4, Rate Similarity Pattern on Land
to the Land Reduction 2 Surface
5. POLICY ANALYSIS AND CHOICE
After the reference scenarios being determined, then the policy analysis is
performed. The analysis result is used as the consideration basis to. determine the
policy choice, The policy formulated in this simulation including :
1. Policy of Land Utilisation
The reclamation activity will cause impacts for biota in such an area and areas
surrounding the reclamation area. The additional land area will cause the wave
hindered on such areas. Therefore it is possible that the surrounding area will
experience the increasing sea water. On the other side, the change of river estuary will
happen
2. Technology Policy
This technology is directly correlated to the investment. With the large capital to be
invested, then it will not only affect the time needed for reclamation, but also will
affect the land surface area
3. Settlement Policy
CONCLUSION
© The model of settlement cycle directs to Limit to success, i.e. the settlement growth
is always limited by the limitation of land available.
© The reclamation activity performed without any strict area planning and regulations
will cause the problem which cause the loss to the activity itself in long term, such
as the case of fixes that files.
e The reclamation activity is the drifting goals activity. The system which is
expected to solve the settlement problem, but in long term - if there is not strict
regulations- will be the environmental problem evolving later.
REFERENCES
1. Kim. H.,Daniel. ArchType Tools, Pegasus, Cambridge, Massachusetts, 1996.
2. Meadows, Dennis L. and Meadows, Donella H. Toward Global Equilibrium,
Wright Allen Press, Cambridge, Massachusetts, 1973.
3. Richardson, George P. and Alexander L, Il. Introduction to System Dynamic
Modelling with Dynamo, Cambridge, Massachusetts: MIT Press, 1983.
4. Senge, Peter. Disiplin Kelima, Translation of Fifth Discipline, Bina Aksara,
Jakarta, 1996. 218
