Hazard Evaluation for Hazard Evaluation for LandslideLandslide

Akiyuki Kawasaki, Akiyuki Kawasaki, Doctoral StudentDoctoral Student

Graduate School of Engineering,Graduate School of Engineering,Yokohama National University, JapanYokohama National University, Japan

Where is Yokohama?Where is Yokohama?

BackgroundBackground

・ Concentrated heavy rain strikes Japan every year

・ Many houses and buildings are damaged and lives

are lost in the landslide and debris flow.

⇒There are two major problems.

・ However, Existing policy is not enough.

⇒Good policy is needed.

1. Problems in Policy

“Hazard zone for landslide” is specified by Municipal government.

It is Not applied for the these areas (In case of Yokohama),

・ less than 5 houses

・ the construction for landslide prevention was done

February 17, 1999

Minami Ward, Yokohama.

2. Problems 2. Problems in Governmental in Governmental OrganizationOrganization

・ Bureaus, Departments, and Divisions of government hardly have a cooperation, even if same municipality.

・ They hardly share their data, because their purpose is different.

PurposePurpose　　

・ Make Collaboration

This study is a Joint ResearchJoint Research between

・ City of Yokohama

Bureau of building

Bureau of road

Bureau of disaster front office

・ Yokohama National University

Tohoku University (Landslide)

Tokyo Institute of Technology (Geology)

PurposePurpose　　

・ Propose a new method “how to create a hazard

evaluation for landslide in urban area from the

Viewpoint as “a Planner”.

・ Utilize “Existing Data”.

・ Make Collaboration

DataData

25 M DEM25 M DEM

横浜国立大学

横浜国立大学

横浜国立大学

(1966 ～ 1999)

Relationship Between Collapse Relationship Between Collapse

and Slopeand Slope

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

14 16 18 20 22 24 26 28 30

Calculated Angle (Degree)

Number of Collapses / ha

Number of Collapses per 1 ha & 1 degree of Calculated Angle

Calculated Angle (Degree)

Total

Collapse

Case

(%)

0102030405060708090

100

7 8 9 101112131415161718192021222324252627282930

Ratio of total Collapses per 1 Degree of Calculated Angle(1966 ～ 1999)

⇒ Actual Angle ≑ ２．５ × Calculated Angle

Factor of Collapse Factor of Collapse

Type 1

Loam

Loam

Mud Stone

Type 2

Mud Stone

Face Soil

Type 3

Three Major Types of Geological Section in Yokohama

Patterns of Patterns of GeologyGeology

＋＋

Records

of Collapse

Specified Hazard Zone(Prefectural & Municipal)

Type 1

Type 2

Type 3

Slump

Slump

Slump

Fall

Patterns of Geology Patterns of

Collapse

地質断面

オーバーハング

あり

母数

オーバーハング

なし

母数 湧水あり 母数 湧水なし 母数

タイプ２

（fall 型）

9

36

12

34

タイプ２

（slump型）

5

35

8

33

タイプ３ オーバーハングありの事例なし

14

64

地質断面

表土厚 50cm以

上

母数

表土厚 50cm未

満

母数

傾斜 60以上（タイプ

２）40以上（タイプ３）

母数

傾斜 60未満（タイプ

２）40未満（タイプ３）

母数

タイプ２

（slump型）

14

25

18

22

タイプ３

51

27

63

15

Hazardous Evaluation for the Risk Hazardous Evaluation for the Risk of Landslideof Landslide

Factor Criterion Type 2 (Fall) Type 2 (Slump)Type 3 (Slump)

SlopeOver 60 (type2)Over 40 (type3)

* 3 5

Under 5m 0 0 0Height 5m-10m 1 1 0

Over 10m 3 3 0Spring Water Existence 1 1 1Past Collapse Existence 3 3 1

Over Hang Existence 3 3 *Thickness of Topsoil Over 50 cm * 3 1

Crack Existence 1 * *

AABB

-Distance from cliff

-Density of buildings

-Structures of buildings

-Building use

For example, Hospital, Welfare Facilities, etc

Consider surrounding environments, as a potential

evaluation of suffering form landslide

Further EvaluationFurther Evaluation

See you next year!See you next year!

Akiyuki KawasakiAkiyuki Kawasaki

Graduate School of Engineering,Graduate School of Engineering,Yokohama National University, JapanYokohama National University, Japan

E-mail: akiyuki@arc.ynu.ac.jpE-mail: akiyuki@arc.ynu.ac.jp

URL: http://gisserv.jks.ynu.ac.jpURL: http://gisserv.jks.ynu.ac.jp

Yes

No

Yes

No

Yes

No

The problems

“Hazard zone for landslide” specified by local government.

It is not applied for the these areas,

・ less than 5 houses

・ Apartment

・ The area where the construction for landslide

prevention was done

⇒ Actual Angle ≑ ２．５ × Calculated Angle

- Propose to Create a New Methodology from the Viewpoint as a “Planner”.

- Collaborative Project Between Prefectural and Municipal Government and Universities.

SummerySummery

Hazard Evaluation for Hazard Evaluation for LandslideLandslide

Akiyuki Kawasaki,Akiyuki Kawasaki, Doctoral StudentDoctoral Student

Graduate School of Engineering,Graduate School of Engineering,Yokohama National University, JapanYokohama National University, Japan