UniversitasGadjahMada FacultyofEngineering* …istiarto.staff.ugm.ac.id/docs/drr/DRR04 Debris Flow DRR.pdfSandpocketatPuFhRiver,MranggenVillage,whosestoragecapacityis4.500.000m

Universitas Gadjah Mada Faculty of Engineering Master of Engineering in Natural Disaster Management h<p://mtpba.B.ugm.ac.id/en/

Drought, Flood, and Debris Flow DRR Debris Flow Disaster Risk ReducFon

13-‐Ju

n-‐15

h<p://isF

arto.staff.ugm.ac.id

1


Mt. Merapi in Ac:on Photos from various sources

13-‐Ju

n-‐15

h<p://isF


2

13-‐Ju

n-‐15

h<

p://isF


3 Areas affected by Mt. Merapi erupFon in 2010 (Kompas, 6-‐Nov-‐10 p. 15)

13-‐Ju

n-‐15

h<

p://isF


4

Upper reach Gendol River, post erupFon, 2010

13-‐Ju

n-‐15

h<

p://isF


5 Code River at Juminahan Yogyakarta, 5-‐Nov-‐10 (Kompas daily, 6-‐Nov-‐10 p. A)

13-‐Ju

n-‐15

h<

p://isF


6 Code River Yogyakarta, 5-‐Nov-‐06 (Kompas daily, 6-‐Nov-‐10 p. 2)

13-‐Ju

n-‐15

h<

p://isF


7 Area affected by Mt. Merapi erupFon in 2006 (Kompas daily)

§  One observes lava flow during erupFon. §  Lava material in various sizes, from rock, boulder, gravel, sand, deposits at

around summit. §  This deposit easily collaps due to tremor or vibraFon of volcanic acFviFes. §  Fast-‐moving lava material is known as pyroclasFc flow; the material

consists of gas to rock. §  PyroclasFc flow is accompanied with high-‐temperature clouds. §  Fresh lava material may induce a very high temperature cloud that is

capable to set forest along its path on fire. §  PyroclasFc flow reaches approximately 3 to 4 kilometers from the summit. §  PyroclasFc flow recedes and forms deposit. §  Heavy rain on this deposit may trigger debris flow known as lahar flood.

13-‐Ju

n-‐15

8

h<p://isF


Lahar flood

§  Lahar flood is a debris flow. §  Debris flow is mixture of water and solid material such as sand, gravel, rock,

and uprooted trees. §  Debris flow velocity may reach 20 to 40 km/h and have huge kineFc energy. §  Debris flow is not an individual transport of sediment, but collecFve mass

transport of sediment; it is triggered by weight (gravitaFonal force) of the mixture.

§  Debris flow may be triggered by: •  deposit of sediment in the upper reach flows due to run-‐off •  landslide •  breach of sabo dam, consolidaFon dam, retaining wall

13-‐Ju

n-‐15

9

h<p://isF


Lahar flood

(Figure: Proyek Merapi; AnimaFon: IsFarto)

high-‐temperature cloud volcanic ashes gravel

lava

13-‐Ju

n-‐15

h<

p://isF


10

primary danger

14-‐Ju

n-‐15

h<

p://isF


11 (Figure: Proyek Merapi; AnimaFon: IsFarto)

secondary danger

13-‐Ju

n-‐15

12

h<p://isF


Pabelan Bridge (Yogyakarta-‐Magelang), 2011, was damaged by lahar flood. §  one span (Yogyakarta-‐Magelang secFon)

collapsed §  one pier (Magelang-‐Yogyakarta secFon) was

damaged


Mt. Merapi: Sabo Works

Photos from various sources

13-‐Ju

n-‐15

h<p://isF


13

14-‐Ju

n-‐15

14

h<p://isF


Photo: STC

Principles of lahar flood control in Mt. Merapi

13-‐Ju

n-‐15

15

h<p://isF


(Figure: Proyek Merapi)

deposiFon zone transportaFon zone producFon zone

13-‐Ju

n-‐15

h<

p://isF


16

River Number of sabo dams

Gendol 20

Kuning 15

Boyong 43

Krasak 25

Bebeng 11

SummaFon 114

13-‐Ju

n-‐15

17

h<p://isF


Sabo dams

Kepala Balai Sabo (Kompas daily, 10 November 2010, p 14).

13-‐Ju

n-‐15

18

h<p://isF


original bed design bed

§  Structures •  Check-‐dams

•  sediment storage dam: to contain the sediment •  sediment control dam: to control the lahar flow

§  ObjecFves •  Sediment storage •  To control lahar flow, reduce lahar flood peak •  To dissipate kineFc energy of lahar flow •  To keep flow on the main channel, to keep lahar flow from becoming

off-‐channel flow

13-‐Ju

n-‐15

19

h<p://isF


Sabo works in the produc:on zone

§  Structures •  Check-‐dams •  River training •  Embankments, dikes •  Groynes

§  ObjecFves •  To containe, to store sediment •  To control sediment (lahar) flow •  To avoid sediment from spilling over the river banks •  To stabilze river reach •  To protect river banks from scouring

13-‐Ju

n-‐15

20

h<p://isF


Sabo works in the transporta:on zone

§  Structures •  Sand pocket •  Channel works •  Dikes, embankments •  Groynes

§  ObjecFves •  To containe, to store sediment •  To control sediment (lahar) flow •  To avoid sediment from spilling over the river banks •  To stabilze river reach •  To protect river banks from scouring

14-‐Ju

n-‐15

21

h<p://isF


Sabo works in the deposi:on zone

§  Structures •  ConsolidaFon dam •  Groundsill •  Girder

§  ObjecFves •  River bed stabilisaFon •  ProtecFon againts erosion and river bed degradaFon •  ProtecFon of other structures at the upstream side

13-‐Ju

n-‐15

22

h<p://isF


River bed stabiliza:on

Structure Main func:on Placement Stepped dam ProtecFon against verFcal and horizontal erosions.

ProtecFon against enlargement and extension of creek. Upstream reach, creeks, valley of V shape.

Checkdam Sediment control: to stop, to store, to control sediment. DissipaFon of kineFc energy (of debris flow). ReducFon of debris peak discharge.

River channel. River cross secFon of U shape.

River bed stabilisaFon (groundsill/consolidaFon dam/bo<om controller)

River bed protecFon. Control of flow.

Downstream of sructure or river being protected.

Sand pocket To avoid sediment spill over river banks. Provide sediment storage.

Alluvial terrain.

Channel works River stabilisaFon. Alluvial terrain.

Training dike To avoid sediment flow spill over river banks. To keep sediment flow in the channel.

Where spill is eminent.

Bank protecFon ProtecFon of river banks from erosion. Where bank erosion is eminent.

13-‐Ju

n-‐15

23

h<p://isF


Sabo works

13-‐Ju

n-‐15

h<

p://isF


24 Check-‐dam at Boyong River, BO-‐D7: open-‐type check-‐dam; the slit provides sediment passage during normal flow.

Photo: STC

13-‐Ju

n-‐15

25

h<p://isF


Check-‐dam BO-‐D7, aBer 2010 erupFon

13-‐Ju

n-‐15

h<

p://isF


26 Check-‐dam at Boyong River, BO-‐D4: closed-‐type check-‐dam Photo: STC

Sand pocket at PuFh River, Mranggen Village, whose storage capacity is 4.500.000 m3

13-‐Ju

n-‐15

h<

p://isF


27 Photo: STC

Check Dams 13-‐Ju

n-‐15

h<p://isF


28

Closed-‐type vs open-‐type check dams (laboratory model test)

Photo: STC Photo: STC

Channel works at Boyong River

13-‐Ju

n-‐15

h<

p://isF


29 Photo: STC

14-‐Ju

n-‐15

30

h<p://isF


Groundsills at Boyong River, behind Engineering campus

BO-‐GI5

BO-‐GS4

BO-‐GS3

BO-‐GI4

GI : girder GS: groundsill

§  www.sabo-‐int.org

13-‐Ju

n-‐15

31

h<p://isF


Sabo Works

13-‐Ju

n-‐15

32

h<p://isF


Photo: STC

Documents

Universitas*Gadjah*Mada Faculty*of*Engineering* …istiarto.staff.ugm.ac.id/docs/drr/DRR04 Debris Flow DRR.pdfSand*pocketatPuFh*River,*Mranggen*Village,*whose*storage*capacity*is*4.500.000*m

UniversitasGadjahMada FacultyofEngineering* …istiarto.staff.ugm.ac.id/docs/drr/DRR04 Debris Flow DRR.pdfSandpocketatPuFhRiver,MranggenVillage,whosestoragecapacityis4.500.000m