10th Asian Regional Conference of IAEG (2015)

Erosion Zone Arround Upper Cisokan Dam, West Java, Indonesia
Ichsan ALFAN(1), Novian TRIANDANU(1), and Dicky MUSLIM(2)(1)Faculty Geology, Padjadjaran University, Jatinangor 45363, Indonesia
E-mail :ichsanalfan@gmail.com(2)Postgraduate Program of Geology University of Padjadjaran, Bandung 40115, Indonesia

Abstract
Study area is located in Cisokan drainage area, Bandung, West Java Province,Indonesia. Potential disaster that may occur around the study area is soil erosion and in
this reaserch area upper Cisokan Dam is under development therefore the study of soil
erosion is necessary. The objective is to characterize and to determine erosion zone that
may affect to the study area. Some methods are used in this research such as desk study,
field work and laboratory analysis. Desk studies consist of morphography analysis using
Digital Elevation Model. Field works consist of Outcrops analysis, Survey of landuse
area and measurement of actual erosion. Lab analysis consist correlation between
geological factor, landuse and actual erosion to make deliniation for erosion zone.
Result of this study shows that the lithology of this area is dominant by Miocene
Sandstone which is erodible. Slope, elevation, geological structure, ground water
facies , soil characteristicsand high rainfall which are developed in the study area are
affects to erosion level. From this reasearch we can conclude that elevation in theresearch area has 400 – 1025 above sea level. Slope zonation in this study area isdevidedinto two zones, namely steep and very steep slope.Steep slope occupy in 55%
west study area. Very steep slope occupy in 65 % east study area. Opening land andvegetasion of this area increase erosion level which endanger Upper Cisokan Dam
developement around the research area.

Keyword: Soil Erosion, Upper Cisokan Dam, Indonesia, Geohazard

1. Introduction
Erosional process in earth happens graduallyand caused by some water and wind activity.
Erosional process can be divided into two,geological erosion or normal erosion andaccelerated erosion.
Normal erosion occurs naturally andcontinuously, forming topographic landform andproducing sediment material. Water, wind andgravity are the main transport media.
Accelerated erosion in tropical regioncommonly caused by surface water activity.
Water is the main transport media and play
important role. Splash erosion, sheet runoff,interill erosion, rill & gully erosion, riverine
erosion, wave action, foreshore erosion or beacherosion, and piping or tunnel erosion are kinds ofwater mediated erosion.

Soil erosion is the common geological hazard
in tropical region and has major impact in area
where it occurs. High rainfall intensity, steeply
slope, and vegetation loss due to terrain utilization
are factors that modified terrain characteristics instudy area, forming sloping morphology that
potentially act as gliding plane and may cause
landslide, damaging village around, infrastructure
and material loss.
The building of Upper Cisokan Dam locatedin study area. Power plant that supply 1040
Megawatt for Java-Bali Region is underdevelopment. Potential disaster that may occur
around this area is soil erosion and slope stability
problem and considering in development ofUpper Cisokan Dam, this research become
necessary.

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10th Asian Regional Conference of IAEG (2015)

Project Area
West Java Province

mode and when collaps can performing blackstart..
Upper Cisokan catchment area is about
10,5 km2, fluctuation of water level in normal
elevationl +777,5 masl and in the lowest
condition at elevation +777,5 masl, Lower dam
has 98,00 m concerete gravity, top Dam lenght
294,00 min elevation +503 masl, widecatchment area 355 km2 and normal water levelat elevation +499,5 m and lowest water levelelevation +495,00 masl.

UPLTA Upper Cisokan Dam development
Figure 1.Reasearch map location (not for scale)
Upper Cisokan Dam development takeplaces in upper Cisokan River that belongs toCitarum Drainage System, West Java Pro vinceIndonesia.The main component of Upper Cisokan
Damare Upper Dam that take places inCirumanis River while the Lower Dam takeplaces in Cisokan River.
Upper Cisokan Power Plant development
head for supplying 1040 Megawatt to Java andBali.PLTA Plta upper cisokan can store energy at
the peak load , by pumping water from reservoirs
from upstream to downstream as the depositary ofenergy and use excess energy at the base load ,itcan be benefits as providers of electric power at
the peak load, controled frequency, dynamic
response, serves as generating facilities stand byFigure 2. Curve daily load with annual
maximum load

Figure 3. PLTA Cisokan works system2

10th Asian Regional Conference of IAEG (2015)

Figure 4. Layout of Construction Areas Upper and Lower Reservoirs (PT. PLN (Persero), 2010)
2. Methodology
Methodology consist of Literature study,fieldwork, and laboratorium analysis. Literature
study done before fieldwork to collect secondary
data consist of DEM analysis and geologicalregion map quadrangle analysis. Fieldwork
consist collect field data, outcrop analysis,landuse
and actual erosion measurement.Lab analysis
consist of data processing to analyze relation
about geological factors, landuse and erosion
factor to know the potential erotion zone.

into two parts based on van zuidam ( 1985 ) ,namely a steep slope 20 % -50 % dominant in theeast the study area occupies 48 % the study
areas .And the very very steep slope 50 % 140 % . Occupy 52 % of all research area.
Upper Damdevelopement
Lower Dam
Developement

3. Result and Discussion
3.1 Geomorfological and Geological Setting
Morfography reasearch area showselevation between 400-1025 masl, according Van
Zuidam classification (1985) the morphology
consist of hill until high hill. Morfometri divided

Figure 5. Digital Elevation Model Map3

10th Asian Regional Conference of IAEG (2015)

Upper damdevelopement

Lower damdevelopement( Not for scale )Figure 6. Geological Reasearch area based on Geological of Cianjur Quadrangle Sudjatmiko 2003; Modified
Based on physiography the study areas
including into bogor zones andsouthern
mountains zone.According to sudjatmiko( 2003 ) in geological of Cianjur quadrangle
map, research area consist of three formations
namely Rajamandala formation,Citarumformation,and Jatiluhur formation. Geological of
Cianjur quadrangle map ordered from elder toyounger stratigraphy at the research area:
1. Clay, marl; quartz sandstones member ofRajamandala formation
2. sandstone and marl member of Citarum
formation

3.

Basalt and breccia sandstone member of
Jatiluhur Formation
4. Pumice tuff and tuffaceous sandstone
5. Tuffaceous breccia, lava, sandstone andconglomerate.
The existence of a structural geology in thereasearch area consist of joint , fold and fault makethe research area has complexity in tectonic
history .A geological fault in meet the area will be
used as upper reservoir.This should be evaluated forits harm in the construction of upper Dam reservoir.

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10th Asian Regional Conference of IAEG (2015)

3.2 Erosive Proses and Analysis

Upper damdevelopement

Lower damdevelopement

Figure 7 . Landuse map of reasearch area.
CodeIndicators

0

No roots are exposed; No crusting; No pedestal sprinkling; cover by vegetation more than
70% (Canopy and surface).

½

Little roots exposure; crusting; no pedestal sprinkling; soil on plants vegetation the upward
plants slope higher than ground; cover by vegetation 30-70 %1

Roots exposure;pedestal sprinkling; ground covered by plants with 1 to 10 mm depth;
Little crastng, cover by vegetation 30 – 70 %.

2

Roots exposure dan sprinkling pedestal dan pile of the ground 5 cm; covered by vegetation
30 – 70 %.

3

Roots eksposure; sprinkling pedestal, pile of the ground with 5 - 10 cm depth, 2 – 5 mm
width krastng, grass in the lower slope covered by material washing product come from thetop slopes;cover by vegetation30 – 70 %4

Roots exposure; sprinkling pedestal, pile of the ground 5 - 10 cm depth, coarse material

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are exposure; rill erosion more than 8 cm depth; open field.
5Trench Erosion (”gully erosion”), rill erosion more than 8 cm depht, open field.

Table 2. Parameter of erosion code and its idicators.
Erosion can be classified based on sign ofactual erosion such as rill erosion, a sheet erosion,and gully erosion in the field , from the data we cangroup into several codes and an indicator as
explained in table above based on the intensity oferosion.Erosion in the study areas in general can beclassified into:
1. Very light erosion ( code 0 ). no roots exposure;no krusting; no sparking pedestal; more than
70 % of the canopy and cover by vegetation,
consist of a steep slope ( 20 % to 50 % ) Occupy
4.8 % of all the research area..
2. Light intensity of erosion (Code ½ and 1) .The
roots exposure; krusting; spraking pedestal;theupward plants slope higher than ground; theground covered by plants with 1 to 10 mm

depth; 30-70% average cover by vegetation,with a steep slope (20% - 50%), occupy 2,55 %of all research area.
3. Middle intensity of the erosion (Code 2 and3).Roots exposure, sparking pedestal and a pileof ground with the depth of 5 and 10 cm, thethickness of krasting 2 – 5 mm, grass in thelower slope covered by material washingproduct come from the top slopes;cover byvegetation30 – 70 %.A steep slope (20% 50%),occupy 20,33 % of all research areas.
4. Heavy intensity of erosion (Code 4 and 5).Thereis no roots exposure; no krusting; there is nosparking pedestal; Cover by vegetation less than
70% of the canopy, with a steep slope (20% 50%), dominant in the eastern research area
occupy 26, 7% percent of all research area.

Explaination :Upper Dam
Developement

Pic a.

Lower Dam
Developement

Pic a. Very weak of erosion
intensity area

Pic b.
Pic b. Light oferosion intensity area

Gambar 8. Erosion zone arround reasearch area

Pic c.
Pic d.

Pic f.

Pic e.

Pic e, f. Heavy intensity of erosion area, there is agully erosion
6Pic c, d. Midle of erosion
Intensity area10th Asian Regional Conference of IAEG (2015)

3.3“heavy use area” where animals are held toprotect pastures when soils are wet or plants
are recovering from grazing. For more
information, see the Horses and Livestock
section.

Erosion Prevention

Here’s a sampling of conservation practices
that can be used. They are more effective whenused in combination:
1. Filter strips and buffers slow water speed,filter pollutants, and trap sediment. They canbe used to stop sediment from leaving thefarm. Grass filter strips are effective onslopes less than 10 percent. Riparian buffersof native trees and shrubs protect streams andmay be 40 to 300 feet wide, based on site
conditions and stream width.
2. Grassed waterways are flat-bottomed
channels planted with grass that are designed
to slow water down to prevent gulleyformation. Farm equipment can drive overthe side slopes during the dry season.
Waterways may need to be combined withrock linings or drop structures on steep slopes.
3. Conservation tillage reduces the amount oftillage and leaves at least 30 percent coverfrom crop residue after harvest and during
winter months. Soil loss is reduced by 50
percent compared to bare soil.
4. Contour farming runs rows “on the level”
perpendicular rather than up and down theslope. Crop rows form hundreds of small
dams that slow water and reduce soil loss up
to 50 percent.
5. Cover crops temporarily protect the soil until
the main crop is planted. Cover crops also
add organic matter and reduce weed growth.
Plant cereal grains and legumes for wintercover crops. Buckwheat is a good summer
cover crop.
6. Pasture management balances livestocknumbers, forage, and water for a healthy farmincome and environment. Pastures with atleast 70 percent plant cover have littleerosion and produce more forage. Set aside a5.

Acknowledgment, Appendix and References

Conclusion
Based on analysis above, the research area
consist of the sedimentary rocks and tuff material
with steep dipping in the fold and fault structuralgeology area.Research area is susceptible to soil
erosion. An infertile soil condition make people toopen their agriculture, the opening field caused thebad impact which the accelerated erosion canendanger to the local residents and Upper Cisokan
development.The prevention can used some methodesuch as filter strips and buffers slow water speed,
grassed waterways, soil conservation tillage, contour
framing, cover crops and pasture management. Basedon field observations, Upper Cisokan dam
development has high potential of erosion. It needs
well public participation, government and scientist toprevent the occurrence of natural disasters that canendanger life and can harm Upper Cisokan dam
development. Geological factor, steeply slope, highrainfall intensity, and opening field can cause
accelerated erosion.The early prevention is needed tominimize erosion.

Anknowledgement
On this chance the authors would likethanks to Allah S.W.T for all of His Mercy andgrace, and people who have helped us inpreaparing and completing this paper Mr. Dicky
Muslim, Novian Triandanu, Agil Gemilang, andVilia
Yohana.

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Reference
Susilo, Hadi. 2009. The First PLTA Pump
Storage Upper Cisokan 1000 Mw in Indonesia.
Buletin Komite Nasional Untuk Bendungan
Besar. February 2009Hunt, R.E (2007) Geologic Hazard : A
Field Guide for GeotechnicalEngineer. United States, CRC
Press.

Sudjatmiko. 2003. Geological of Cianjur
Quadrangle,WestJava
Province.
Bandung: Geological reaserch anddevelopement center.

Morgan, R.C.P. 2005. Soil Erosion andConservation.USA,
Blackwell
Publishing
Fossen, Haakon (2010) StructuralGeology . Cambridge University Press

Van Zuidam, R. A.. 1985. Aerial PhotoInterpretation in Terrain Analysis andGeomorphologic
Mapping.
SmitsPublishers. The Hague Netherland 442 H.

Attewel, P.B.,& Farmer, I. W., 1976,
Principles of engineering geology,
Chapman& Hall, London

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