Bencana Sedimen di Indonesia dan Usaha Penanggulangannya

Bencana Sedimen di

Indonesia dan Usaha

Penanggulangannya

Oleh:

Jazaul Ikhsan

Jurusan Teknik Sipil, Fakultas Teknik,

Universitas Muhammadiyah Yogyakarta

CCF 2016

CCF 2016

Kampus Terpadu, UMY, 21 Maret, 2016

Indonesia terletak :

 Diantara benua Asia and Australia,

 Dikelilingi Samudera Hindia dan Samudera Pacific,

 Di atas lempeng Pasifik, Eurasian, and

Indo-Australian

Oleh sebab itu terdapat banyak Gunung Berapi, dan mempunyai

Volcano disasters :

 17,985 deaths, Million people affected,

 The economic damage was US $ 344,390,000.

Landslide disasters:

 2,236 deaths; 393,652 people affected

 The economic damage was US $ 121,745,000.

Source: Data of 1900-2010/www.em-dat.net

Earthquake disasters:

 28,700 deaths; 5,621,023 people affected

 The economic damage was US $ 4,672,476,000.

Flood disasters:

 5,902 deaths; 8,731,109 people affected

 The economic damage was US $ 2,418,553,000.

CCF 2016

Permasalahan Sedimen

•

Menurut Salomons (2005), keberadaan

sedimen dalam suatu DAS sangat

“unik”.

•

Terlalu

banyak sedimen

dapat

menyebabkan

masalah

,

terlalu sedikit

juga menimbulkan

masalah

.

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4-75

Tanah longsor, aliran piroklastik dan

debris

Erosi, angkutan sedimen

Sangat besar

Potensi sumber daya sedimen

Sumber daya Jangka pendek

Jangka panjang

Bencana

Pengelolaan bencana sedimen

Pengelolaan sumber daya sedimen Tidak

terkontrol CCF 2016

Types of Sediment Related

Disasters

•

Direct Disaster:

–

Debris flows

–

Landslides

–

Slope failures

–

Pyroclastic Flows

•

Indirect Disaster:

–

Riverbed Agradation/Degaradation

Mount Merapi is one of the most active volcanoes in Indonesia.

It located on the island of Java on the border between Central Java and Yogyakarta Special Provinces.

Its eruptions have produced large amounts of volcanic material such as ash falls, lava, and pyroclastic flows.

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25-75

1820 1830 1840 1850 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 Non Active

1820 1830 1840 1850 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 Active

1820 1830 1840 1850 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 The peak time of eruption

Non Active

Active

Peak of eruptions

CCF 2016

Kampus Terpadu, UMY, 21 Maret, 2016

1900 1950 1992

50 100 YEAR C UMU L A T IVE V O L U ME ( x10 6m 3) 150 0

1900 1950 1992

50 100 YEAR C UMU L A T IVE V O L U ME ( x10 6m 3) 150 0

Annual average lava production 1.2x106

m3_/year

Annual sediment production in non volcanic basin

0.24x106 _m3_/year

The total annual sediment production is estimated at 1.44x106 _m3_{/year (1995).}

Trising 1934 1939 Senowo 1930 1997 1948 1933 1939 Lamat 1930 Blongkeng

1910-1930 _Putih1930 19691984 2001 19671998 19191992 1933 1939 1975 Woro 1901-1906 1900 1942 1961 1939 1939 1939 1942 Gendol 1994 Boyong 1997 Kra sak 1997 1961 Krasak 1963 1961 Batang Bebe ng 1942-431967 1967 1973 1975 ₁₉₇₃ 19701972 ₁₉₆₈

2006 ₂₀₀₆ 10 km N W E S 5 km Pabelan upstream 1954 1936 Apu 1934-35 Trising 1934 1939 Senowo 1930 1997 1948 1933 1939 Lamat 1930 Blongkeng

1910-1930 _Putih1930 19691984 2001 19671998 19191992 1933 1939 1975 Woro 1901-1906 1900 1942 1961 1939 1939 1939 1942 Gendol 1994 Boyong 1997 Kra sak 1997 1961 Krasak 1963 1961 Batang Bebe ng 1942-431967 1967 1973 1975 ₁₉₇₃ 19701972 ₁₉₆₈

2006 ₂₀₀₆ 10 km N W E S 5 km Pabelan upstream 1954 1936 Apu 1934-35 2010 2010 2010

 Pyroclastic flows are due to collapse of lava dome or lava tip.

 A typical phenomenon of pyroclastic flow of Mount Merapi is accompanied by glowing cloud (wedhus gembel).

 The 2006 and 2010 eruptions, the direction of pyroclastic flows is south-eastern.

CCF 2016

Kampus Terpadu, UMY, 21 Maret, 2016

５ ． Ｌ ． Ｂ ｅ ． Ｐ ． Ｐrog o ． Batan g ． Bebe ng ． Krasak ． Bo yon g ． K u n in g ． Ge n d o l ． W o ro ． Yogyakarta Klaten 0 5km N 500 Ｐ ｅ ． ｅ ｗ ． Mount Merapi ５ ． Ｌ ． Ｂ ｅ ． Ｐ ． Ｐrog o ． Batan g ． Bebe ng ． Krasak ． Bo yon g ． K u n in g ． Ge n d o l ． W o ro ． Yogyakarta Klaten 0 5km N 500 Ｐ ｅ ． ｅ ｗ ． Mount Merapi

Phyroclastic flow after Eruption in

July 2006 (Gendol river)

Before phyroclastic flow

After phyroclastic flow

Year Duration of activity (year) Total sediment volume (Mm3₎

Casualties and damages properties 1994 1996 2006 2010 0.9 -0.25 -5.2 -3 140

Turgo village was burned and 66 were killed

6 missing

Kaliadem village was burned, 2 casualties Kepuharjo, Glagaharjo villages were damaged and 270 were killed

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The reasons why the volcano offers favorable condition for debris flow are as follows:

1. Pyroclastic deposits are abundant,

５ ． Ｌ ． Ｂ ｅ ． Ｐ ． Ｐrog o ． Batan g ． Bebe ng ． Krasak ． Bo yon g ． K u n in g ． Ge n d o l ． W o ro ． Yogyakarta Klaten 0 5km N 500 Ｐ ｅ ． ｅ ｗ ． Mount Merapi ５ ． Ｌ ． Ｂ ｅ ． Ｐ ． Ｐrog o ． Batan g ． Bebe ng ． Krasak ． Bo yon g ． K u n in g ． Ge n d o l ． W o ro ． Yogyakarta Klaten 0 5km N 500 Ｐ ｅ ． ｅ ｗ ． Mount Merapi 0 20 40 60 80 100 120 140

1931 1969 1971 1973 1975 1977 1985 1987 1989 1991 1993 1995

Year N u m b er o f d eb ri s fl o w s Trising Senowo Pabelan Lamat Blongkeng Putih Batang Bebeng Krasak Boyong Kuning Gendol Woro Putih River Woro River

The number of debris flows by river in Mt. Merapi

2. Merapi area has high intensity rainfalls, 3. Drainage is very dense.

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Usaha mengurangi resiko:

•

Aliran Pyroklastik: dengan early warning

system (

non struktur

).

•

Debris flow (lahar dingin):

–

Bangunan pengendali sedimen (sabo dam)

(

struktur

)

–

Early warning system (

non struktur

)

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Sabo dams on slopes of Mt. Merapi Early warning system in Mt. Merapi

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Debris Flow/Banjir Bandang

Mt.

Argopura

Non structure measurement

Research Area

,

Mt. Argopur

o

Non structure measurement

Case 1, Qmax: 1762 m3_/sec Case 2, Qmax: 1233 m3/sec Case 3, Qmax: 2613 m3/sec

The areas effected by debris flow in Case 1, 2 and 3

• Generally, almost of Indonesia’s watersheds are still in

natural condition.

•

Indonesia has about 5 590 rivers and 470 watersheds.

•

Lake, dam, wetland = 33 million hectares.

•

Increasing population and development cause number of

critical watersheds always increase year by year.

•

Now (2006), there are 64 critical watersheds

•

Amount of the critical watersheds is most in Java island,

because around 65% Indonesian population (~ 125M

people) live in Java island which is only 7% of total

Indonesia continental area.

Reservoir Sedimentation

(Permasalahan DAS kritis):

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22

39

48

58 62

64

0 10 20 30 40 50 60 70

N

u

m

b

er

1984 1994 1998 2000 2002 2006

Year

Change of Critical Watershed

Watershed

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Bengawan Solo Watershed

Wonogiri Reservoir

CCF 2016

•

The Bengawan Solo flows through Central

and East Java Provinces, is the largest river

on Java with a watershed area of around

16,100 Km

2

and a length of about 600 Km.

•

Bengawan Solo river is one of Indonesia

rivers which have critical watershed. The

problem is indicated by high sedimentation in

Wonogiri reservoir.

•

The Wonogiri reservoir was constructed in

1982

CCF 2016

•

The Dam provides flood control, irrigation,

domestic water supply and hydropower

generation, and gives services to about 710,000

population (1998).

•

The present effective storage capacity of the

reservoir is roughly estimated to nearly about

60% of its original capacity, due to the problem

of sedimentation.

•

Risky Reservoir Operation due to Decrease of

Effective Storage Capacity.

CCF 2016

Satellite Picture on May 13, 2003

Sedimentation

in Progress

Keduang River

(421 km2)

Tirtomoyo River

(231 km2)

Bengawan Solo

(206 km2) and

Intake

Annual Sediment Yield by Source

Other Sources

5% Surface

Soil Erosion

95%

Gully Erosion

32%

Landslide 6% Road Side

Slope 7%

River bank 55%

Sediment Source

Vol.

( x 1000m3 ₎

•

Soil Erosion

2,947

•

Other Sources

232

- Gully

76

- Landslide

15

- River Bank

130

- Roadside Slope

11

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Land slide River bank erosion

Surface erosion

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Restoration:

Actually, restoration is new concept for river management in Indonesia.

Restoration has been tried in watershed of river by watershed management, for example in Bengawan Solo river by developing terrace and forestation.

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0 – 8%

90%

10%

25 – 40%

25% 75%

>40%

100%

15 – 25%

50% 50%

8 – 15%

25% 75%

Fruits/Trees

Seasonal Crops

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Effects of Watershed Management

1980-1990:

6.2 million m3/year

1980-1993:

5.7 million m3/year

Significant Difference resulted from What?

・

Many large floods in early 1980s

・

Watershed management project

in 1989-1994

Historical Change of Storage Capacity of Wonogiri Reservoir

500 550 600 650 700 750

1980 1985 1990 1995 2000 2005

Year S to ra g e C a p a c it y ( m il . m 3 )

1990-2005:

3.4 million m3/year

Terima kasih atas

perhatiannya

CCF 2016