April 8, 2010, Strbske Pleso, Slovakia27th Session of the EFC Working Party on the Management of Mountain Watersheds

Seminar: “Integrated forest and water management of mountain watersheds:Experiences and perspectives”

Landslides and Their Control i M t i W t h d f Jin Mountain Watersheds of Japan

– Processes and Countermeasures –

Hideaki MARUINiigata University

Research Center for Natural Hazards and Disaster Recovery

Japan as Landslide Paradise!- Typical Landscape with densely distributed landslides -- Typical Landscape with densely distributed landslides -

Densely Distributed Landslides on Hilly Terrains in Kubiki Landslides in Tertiary Areas

Zentoku Landslide in Iya-Valley / Landslides in Fractured Zo

Landslides in Volcanic Mountain Area

Sounzan Landslide in Hakone / Landslides in Hydrothermal Alteration zones

Contents of the Report:

- Geology and Geomorphology of Japanese Archipelago

Cli t f J- Climate of Japan

- Charactersitics of Landslides in Japan

- Distribution of Landslides and Geotectonic Structures

- Investigation Measures

Miti ti M- Mitigation Measures

- Representative Landslides and Mitigation Measures

- Perspectives

Trenches and island arcsaround the Japanese Archipelago

Ｋｕｒｉｌｅ Ａｒｃ

NorHonArc

● SendaiMid Nii t ★

rtheastnshu

rc

● Tokyo

Mid Niigata★

SouthwestHonshu Arc

Izum Izu-Mar

Honshu Arc

L

riana Arc

ocat

c

Ryukyu Arc

Major Geologic Zones

(Highest landslide occurrence)

Monthly Mean Precipitationand Temperature

CC ur f Di tr u T hCCourses of Disastrous Typhoo

★

★★

ca. 7000

ca. 320,000 ha

AltogetherAltogether 100 Billion Yen

NorthernFossa Magna↓

Median TectonicLine →

Landslide Prone Areas and Geotectonic Structures

(active)

Syncline

(stable)

Anticline

Neogene Formationg- Black Mudstone- Alternation of

Sandston and Mudstone

•Extremely low shear strength

Distribution of Landslide Areas in Matsunoyama-District in Niigata

Fractured Zone alonggthe Median Tectonic Line

- Metamorphic Rock Formation

Flow Chart for LandslideInvestigation and AnalysInvestigation and Analys

Fukuzono’s Method:

I t f th l ith fIncrement of the logarithm of Accelerationis proportional to Logarithm of Velocity of Surface Displacement

Various Types of Landslide Mitigation MeasuresVarious Types of Landslide Mitigation Measures

Sarukuyoji Landslide in Niigata Prefecture

Length: 1,700 mWidth: 400 m

Neogene Formation-Weathered Black Mudstone

Depth: 4-15 mArea: 44.3 ha

Jizukiyama Landslide

Length: 700 mLength: 700 mWidth: 500 mDepth: 60mArea：25 ha

Upper Tertiary,Late MioceneRhyolitic Tuff

Overview of Odokoro Landslide Plan of Odokoro Landslide andDistribution of Control Measures

Length: 1000 m Crystalline Schist Mesozoic andWidth: 400 – 800 mDepth: deeper than 100 mArea: 60 ha

Crystalline Schist, Mesozoic and Paleozoic Sedimentary RocksSepentine Melange Zone

Plan of Akasaki Landslide

Overview of Akasaki Landslide

Colluvial SoilGreen TuffSandstone

Length: 1100 mWidth: 500 mA 30 hArea: 30 ha

Distribution of

Cross Section of Akasaki Landslide andDistribution of Drainage Wells and Tunnels

Distribution ofControl Measures

A tremendous number of landslides were induced by the Mid-Niigata Prefecture Earthquake

Important target: Earthquake Induced Landslides- Important target: Earthquake-Induced Landslides -

Imo River Basin immediately after the 2004 Mid-Niigata Earthquake（Ministry of Land Infrastructure and Transport）

Distribution of slope failures and landslides caused by the Mid-Niigata Prefecture Earthquake

- Black：Slope failures- Gray ：Main scarp of landslides

Oblique line：Displaced soil mass- Oblique line：Displaced soil mass

（Interpreted by Prof. Yagi)

Overview of Imogawa River

Area of Watershed:38kmm2

Maximum Elevation：680m

Minimum Elevation：75m

Length of channel: 16km

River Bed Inclination：1/70

The largest landslide induced by the strong Vibration of the Mid Niigata Earthquake 2004, Japan(500m x 500m x 100m)

Main scarp of the Higashitakezwa landslide (photographed on 27th October）

Emergency drainage from reservoir by Higashitakezawa landslide

Reservoir formed by the Higashitakezawa landslide damg

Inundation of houses atKogomo- DistrictKogomo- District

Legends: Situation in March 2005

Blue color along river channels: Reservoirg

Landslide dams are shown by circles and triangles:Ci l h Ri Ch l Bl kCircles show River Channel Blockages which are still existing.Orange circle: Countermeasures installedBlue circle: OvertoppingRed circle: Without OvertoppingTriangles show River Channel Blockageswhich are already solved.Green triangle: naturally washed awayGreen triangle: naturally washed awayViolet triangle: artificially excavated

Distribution of Landslide Dams

（Hokuriku Regional Development Bureau)

Accomplishment of Stabilization works at Higashitakezawa

Two and half years after the Earthquake

Remarks for mitigation of future landslide hazards

Reconnaissance and evaluation of slope stability１）Primary reconnaissance after the Earthquake２）Secondary detailed reconnaissance after snowmelt２）Secondary detailed reconnaissance after snowmelt

Landslides and reconstruction of main roads１）Reconsideration of route plan of main roads

）２）Stabilization of landslidesControl and management on landslide dams

１）Monitoring on displaced soil mass） g p２）Monitoring on snowmelt３）Permanent countermeasures

Other remarks:Other remarks:１）Evaluation of danger degree by sediment disasters after the Earthquake）２）Hazard mapping for prediction of landslides in relation

to the next possible earthquake

Accomplishment of Stabilization works at HigashitakezawaAratosawa Landslide – the largest landslide caused by the 2008 Iwate-Miyagi Earthquake

I E h k I d d L d lid- Important target: Earthquake-Induced Landslides -

Two and half years after the Earthquake

Road

Head Scarp Collapse of road

Old landslide scar

p f

Old landslide scar

Displaced soil mass

Reservoir

Topographic displacement of Aratosawa landslide(Japan Landslide Society)

Before earthquake

Old subsidence zoneSliding surface

After earthquake

Compression zone Subsidence zone

TuffSandstone/Siltstone

Welded tuffPumice tuff

Longitudinal profile of Aratosawa landslide (Tohoku forestry bureau)

Tuff

Flow type landslideFlow type landslide

Source area of Komanoyu debris flow

Source area of Ubusumegawa debris flow

Araotosawa Landslide

Epicenter

Active Fault

Muzaffarabad

Location of epicenter area

HattianLandslide

Surface displacement and active faults (Geographical Survey, 2006)

Large scale surface landslides in Muzzafarabad

Hattian landslide – the largest landslide caused by the Northern Pakistan Earthquake

Landslide along main road

Interpretation of Landslide Topography using IKONOS Satellite Image

andandRisk Identification by Analytical Hierarchy Process

Factors for Risk Identification:＊Surface Gradient＊Geological Structure

Danger Degree of Landslide

g＊Location to the River Channel＊Clearness of Surface Deformation

g g f

Active Landslide

（Example in Pakistan)

Objective1:To clarify Mechanism of Earthquake-Induced Landslides

WG8(Review of RecentWG1(Mechanism)

Shear Strength

WG8(Review of Recent Events in Japan)

WG7(Review of

InformationTransfer

gCharacteristics

of Sliding Surface

WG2(Ri k A t)

Overseas Events)

WG6(Historical Analyses of Past Events)WG3(SecondaryWG2(Risk Assessment)

Soft Measures Hard Measures

)WG3(SecondaryDisasters)

InformationTransfer

WG5(Warning/ Evacuation)

WG4(Countermeasures/Design Procedures) Database

Transfer

Guidelines

Objective2: Technical Proposal forDisaster Mitigation

Risk Management for Mitigation of Landslide Disasters Caused by Earthquakesy q

in Asian Orogenic Zone(by the Mid-Niigata Prefecture Earthquake,by the Northern Pakistan Earthquake, etc.)＊Common tasks in Asian Orogenic Zone

＊Severe Landslide Disasters Caused by the Mid-Niigata Prefecture EarthquakeNiigata Prefecture Earthquake－ Emergency Operations.－Response to Successive Disasters－Mitigation of Future Slope Disasters Caused by Earthquakes＊T h l d I f i T f＊Technology and Information Transfer(International Cooperation)

Croatia-Japan Joint Research:Risk Identification and Land-use Planning for Disaster Mitigation of Landslides and Floods in Croatia

Hideaki MaruiProject Leader : Niigata UniversityProject Leader : Niigata University

（Split at Adriatic Cost)

Landslides in mountainous areas along the Adriatic CostApparent danger to the main roads

Interruptive factor against development in Croatia

Grohovo Landslide (southwest side)faced to the Rjecina River near Rijeka City

Summary-: Scheme of ResearchO

Ob tiSurvey oTriggers

Survey o

Objective

Runoff in Karst Areas

Observationof Triggers

UrbanizationDevelopmentTopography

Rainfall

社会シ

題・防

of s ofes

降雨（地下水）

Landslides Floods

Rin

Ma

Rainfall(Groundwater)

ステム・人

防災政策Flash-Flood

Risk Assessment

Landslide Risk

A t

Floodsng Shear

athematica

人口問

Risk AssessmentAssessment

Flash-Flood

Apparat

al ModelLandslide Integrated

L d lid Fl d Hazard Map

tus

Risk Identification and Land Use Planning for Disaster Mitigation

Hazard MapLandslide-Flood

Hazard Map

安全な地域社会構築にむけた実用的かつ安価な防災技術のアジア（東北アジア３国＋アセアン３国）共同開発

Risk Identification and Land-Use Planning for Disaster Mitigationof landslides and floods in Croatia

（Formulation of Land-Use Guidelines for Mitigation of Disasters）

We are very grateful to you for your kind attentionfor your kind attention