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2014暑期坡地營課程06/08/2014

Models for Predicting Landslide Location (1)

Chyi-Tyi Lee

Graduate Institute of Applied Geology,

National Central University, Taiwan

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Landslide Hazard Map of Europe

(www.safeland-fp7.eu)

Summary report October 2012

EUROPE

3(Kawagoe et al., 2010)

Landslide Hazard Map of Japan

JAPAN

0.0000

0.0050

0.0100

0.0150

0.0200

0.0250

0 1 3 5 6 7 8 9 10

山崩潛感分級

崩壞

比

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Landslide susceptibility map built by using slope and lithology (Liao et al., 2001)

The First Landslide Susceptibility Map of TaiwanIn 2001

LithologyGroup A Hard Miocene, Pre-Miocene, Igneous Rocks

Group B Soft Sandstone, Conglomerate

Group C Soft Mudstone and Shale

Rating for Slope FactorSlope 0-3 3-10 10-15 15-20 20-30 30-40 >40

A 0 1 3 6 7 8 9

B 0 3 5 7 8 9 10

C 0 5 7 8 9 10 10

Landslide Hazard Map of Taiwan

Susceptibility Class

La

nd

slide

R

atio

Landslide Ratio vs. Susceptibility Class

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Susceptibility Analysis

Hazard Analysis

Risk Analysis

Inventory Construction Construction of time series inventory of hazard

Dividing a region into successive classes representing different grades of slope instability

Calculation of the probability of a hazard level in a given region and a given time period.

Calculation of the lost of life or property in a given region and a given time period.

Keywords and Steps in Natural Hazard Analysis

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• Landslide hazard analysis is a regional hill-slope stability analysis concerning the probability of instability at any given point in the study region and in a given time period.

What is a Landslide Hazard Analysis?

It is different from a conventional slope stability analysis.

• Slope stability analysis is a site-specific stability analysis concerning under what condition the slope will become unstable.

Landslide probability for 100-year rainfalls, Tachia drainage basin, Taiwan.

Limit equlibrium slope stability analysis

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Yunlin

475-year earth-quake

How a Landslide Hazard Model Predicting Landslide Location?

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• Qualitative methods• Geomorphologic interpretation• Expert’s point system

• Quantitative methods• Conditional probability (bivariate analysis)• Discriminant analysis (multivariate analysis)• Logistic regression (multivariate analysis)• Neural networks (artificial intelligence)• Fuzzy set theory (artificial intelligence)• Infinite slope model (limit equilibrium calculation)

☆ The susceptibility analysis aims at dividing the region into successive classes representing different grades of slope stability, spatial and temporal occurrence probability are not discussed. It is different from a landslide hazard analysis.

坡 度

岩 性

坡 向

地 表 覆 蓋

距 侵 蝕距 離溝

距 道 路距 離

距 斷 層距 離

山崩

潛感

圖

Previous Works on Landslide Susceptibility Analysis

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Map showing probability of seismic triggering of landslides in Northridge-earthquake shaking conditions in part of the Oat Mountain quadrangle.

Jibson, R.W., Harp, E.L., Michael, J.A. (2000) A method for producing digital probabilistic seismic landslide hazard maps, Engineering Geology, 58, 271-289.

Landslide occurrence probability for 475-year return period earthquake intensity.

Liao, C.W., Lee, C.T. (2004) Probabilistic hazard analysis of earthquake-induced landslides - an example from KouHsing, Taiwan, International Symposium on Landslide and Debris Flow Hazard Assessment, 7-1~ 7-9.

Recent Landslide Hazard Analysis (1/5)

Deterministic approach for earthquake-induced landslides●

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Deterministic approach for storm-induced landslides

Montgomery, D. R. and Dietrich, W. E. (1994) A physical-based model for the topographic control on shallow landsliding, Water Resour. Res., 30, 4, 1153-1171.

Schmidt, J., Turek, G., Clark, M. P., Uddstrom, M. and Dymond, J. R.: Probabilistic forecasting of shallow, rainfall-triggered landslides using real-time numerical weather predictions, Nat. Hazards Earth Syst. Sci., 8, 349–357, 2008.

Recent Landslide Hazard Analysis (2/5)

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Probabilistic approach for earthquake-induced landslides

Lee, Chyi-Tyi, Huang, C.C., Lee, J.F., Pan, K.L., Lin, M.L., Dong, J.J. (2008) Statistical approach to earthquake-induced landslide susceptibility, Engineering Geology, 100, 43-58.

Yunlin475-year

earth-quake

Lee, Chyi-Tyi (unpublished).

Recent Landslide Hazard Analysis (3/5)

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Probabilistic approach for storm-induced landslides

Guzzetti, F., Reichenbach, P., Cardinali, M., Galli, M., and Ardizzone F. (2005) Probabilistic landslide hazard assessment at the basin scale, Geomorphology, 72, 272-299.

Fig. 5. Exceedance probability of landslide occurrence obtained computing the mean recurrence interval of past landslide events from the multitemporal inventory (Fig. 3), assuming it will remain the same for the future, and adopting a Poisson probability model (Eq. (9)). Shades of grey show exceedance probability for different periods: A) 5 years, B) 10 years, C) 25 years, D) 50 years. Square bracket indicates class limit is included; round bracket indicates class limit is not included.

5 years 10 years

50 years25 years

Exceedance probability

- using multi-temporal landslide inventory

Recent Landslide Hazard Analysis (4/5)

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Probabilistic approach for storm-induced landslides

Dai, C.F. and Lee, C.F. (2003) A Spatiotemporal Probablilistic Modeling of Storm-Induced Shallow Landslide Using Aerail Photographs and Logistic Regression, Earth Surf. Proc. Land., 28, 527-545.

Chung,Y.C., Huang, C.M., Lee, Chyi-Tyi (2009) Validation of landslide prediction model under different rainfall scenarios. Joined Annual Meeting and Conference of the Geological Society of China and the Geophysical Society of China, HZ13-O, 11p.

- using event-based landslide inventory

5 years 10 years

50 years25 years

10 years 100 years

香港大嶼山

台灣北部石門水庫集水區

Recent Landslide Hazard Analysis (5/5)

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• Deterministic approach: Limit equilibrium analysis of infinite-slope at a region using strength and hydrologic parameters to obtain a safety factor for a given point under rainfall or earthquake condition.

• Direct probabilistic approach: Using a long-period multi-temporal landslide inventories to analyze the landslide occurrence probability for each slope under certain return period.

• Spatial-Temporal probabilistic approach: To analyze the spatial landslide occurrence probability and the rainfall temporal probability separately. Landslide occurrence probability is obtained via event-based landslide susceptibility analysis. Temporal probability is obtained by hydrological frequency analysis of rainfalls.

Summary of Methods for Landslide Hazard Analysis

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Susceptibility Analysis

Hazard Analysis

Risk Analysis

Inventory Construction Construction of a landslide inventory.

Dividing a region into susceptibility classes by using a landslide inventory and some landslide causative factors.

Calculation of spatial and temporal probability of landslide in a given region.

Developing a Landslide Hazard Model

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The Use of a Landslide Inventory in Susceptibility/Hazard AnalysisMulti-temporal landslide inventory was commonly used in

developing a susceptibility/hazard model. The long the period covered, the better the temporal significance is.

Single-period landslide inventory: Landslide inventory from single period of aerial photos or a satellite image is not valid for training a landslide susceptibility model (e.g., Canuti and Focardi, 1986). For example,

Ruey-Li earthquake Chi-Chi earthquake Toraji-Lekima typhoon

High

Mod. High

Moderate

Low

Stable

Susceptibility class

Landslide susceptibility maps of Yunlin quadrangle trained from landslide inventory of different period.

(1/2)

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The Use of a Landslide Inventory in Susceptibility/Hazard Analysis

(2/2)

Single-period landslide inventory for susceptibility analysis is biased. However, it may not be feasible to use a multi-temporal landslide inventory in some regions. This is especially true in Taiwan (Lee and Fei, 2011), and therefore, an event landslide inventory must be considered.

Event landslide inventory is feasible in developing an event-based susceptibility/hazard model (Lee et al., 2008a, 2008b). The temporal significance may come from the triggering factors used in building the model.

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Landslide Types Considered in Susceptibility/Hazard Analysis

Deep-seated landslides are commonly controlled by local geological structures. They were usually not considered in building a susceptibility/hazard model.

Debris flows are different with slide and fall type of landslides in many aspects, like location and controlling factors. Their susceptibility/hazard analysis was commonly performed along.

Shallow landslides are commonly of random features occurred on hill slope. They were the target in building a susceptibility/hazard model. Rock falls have similar random behavior with shallow landslides. The were usually included in the shallow landslide group for analysis.

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Hilly terrain

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0.2

0.4

0.6

0.8

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0 0.2 0.4 0.6 0.8 1Portion of areas predicted as hazard area

Por

tion

of

land

slid

es w

ithi

nth

e pr

edic

ted

haza

rd a

rea

NN LOGISTIC DN DA

LOGISTIC : Logistc RegressionDA : Discriminant AnalysisNN : Neural NetworkDN : Newmark Displacement

Kuohsing Quadrangle, Hilly Terrain

123Portion of areas predicted as hazard

Po

rtion

of lan

dslid

es with

in

the p

redicted

hazard

are

a

(Lee, 2006)

Selection of an Analytical Method

Logistic regression is an effective and robust method for building a susceptibility/hazard model. NN may built a success model but sometimes fail in prediction. DN commonly involves problems of lacking local soil depth, strength parameters, and groundwater data.

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Selection of a Mapping Unit A mapping unit refers to a portion of the land surface which contains a set of ground conditions which differ from the adjacent units across definable boundaries (Hansen, 1984).

Grid-cells, divide the territory into regular squares of pre-defined size.

Terrain units, favored by geomorphologists, are based on the observation that frequently reflect geomorphological and geological differences.

Unique-condition units, are homogeneous domains derived from classification of many slope-instability factors.

Slope-units, automatically derived from high-quality DTMs, partition the territory into hydrological regions between drainage and divide lines.

Topographic units, are further subdivided into homogeneous morphometric domains from the slope units.

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Computer Software Needed

Vector GIS: MapInfo, ArcGIS, and others, for mapping of landslides and output of thematic maps.

Image Processing and Raster GIS: Erdas Imagine, and others, for processing of satellite images, and for processing of landslide causative factors from DEM and others.

Statistical Package: SPSS, SAS, MATLAB, and others, for statistical tests and multivariate analysis, like logistic regressing and discriminant analysis.

Others, like Fortran code designed for specific data processing or analysis.

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Thanks for your attention!