GUIDELINES FOR MAPPING AREAS at RISK of LANDSLIDES 22th – 24th October 2007 JOINT RESEARCH CENTRE Institute for Environment and Sustainability, Land Management and Natural Hazard Unit ISPRA (VA), Italy
Landslide susceptibility, hazard & risk GIS mapping in the Betic Cordillera (Spain): areas with limited information about triggering factors
José Chacón University of Granada Spain . 1/65 Geographical setting
Andalusia (South Spain)
Central and Western Betic Cordillera
Population, climate, orography
2/65 Spain 3/65 Andalusia Administrative divisions in Andalusia (data from 2006)
Densidad h/km 2
72,5 160,5 57,3 69,3 48,6 49,1 204,1 130,7
Andalucia Sevilla 7975672 87600,47 92,1
770 municipalities all with political competencies in land-use planning 4/65 The orography of Andalusia: mountains in the East, valley in the West
Mediterranean Sea
0 – 400 m 1600 – 2200 m 400 – 1000 m 2200 – 2800 m Source Junta de Andalucia. 5/65 Consejería de Mediambiente. Spain 1000 – 1600 m 2800 – 3487 m High variety of climate conditions at short distances
6/65 Source Junta de Andalucia. Consejería de Mediambiente. Spain Averaged yearly rainfall 1961-2001
Lowest values in Tabernas Desert Top values in <200 mm/yr Grazalema Sierra < 250 mm 250 - 500 mm >2000 mm/yr 500 - 750 mm > 750 mm
Climatic variability in Andalusia (Spain) 7/65 Guadiana River basin n Segura River basi ver basin r Ri uivi dalq Gua
ins bas hern Sout Athlantic Ocean Mediterranean Sea
The orography0 – 400 of Andalusia:m 1600 – 2200 m 400 – 1000four m different hydrographic2200 – 2800 divisions m 1000 – 1600 m 2800 – 3487 m 8/65 High climate variability with topography or exposition at province level: Granada
Mountain Mediterranean
Continental Mediterranean
Moderate Mediterranean
Subtropical Mediterranean
Semiarid Mediterranean
40 kms
9/65 Variability in between villages at short distances: Example Southern Granada province
·Trevélez
·Cádiar
10/65 ALBUÑUELAS (máxima 24 anual) VÉLEZ (máxima 24 anual) PADUL (máxima 24 anual)
160,00 200,00 160,00 180,00 140,00 160,00 140,00 120,00 140,00 120,00 100,00 120,00 100,00
mm 100,00 mm mm 80,00 80,00 80,00 60,00 60,00 60,00 40,00 40,00 40,00 20,00 20,00 20,00 0,00 0,00 0,00 1941/42 1945/46 1949/50 1953/54 1957/58 1961/62 1965/66 1969/70 1973/74 1977/78 1981/82 1985/86 1990/91 1994/95 1943/44 1947/48 1951/52 1955/56 1959/60 1963/64 1967/68 1971/72 1975/76 1979/80 1983/84 1987/88 1991/92 1996/97 2001/02 AÑO 1940/41 1945/46 1949/50 1953/54 1957/58 1961/62 1965/66 1969/70 1973/74 1977/78 1981/82 1985/86 1989/90 1993/94 1997/98 2001/02 AÑO AÑO CÁDIAR (máxima 24 anual) TREVÉLEZ (máxima 24 anual) LANJARÓN (máxima 24 anual) 250,00 300,00 300,00 250,00 200,00 250,00 200,00 150,00 200,00 mm
mm 150,00 mm 150,00 100,00 100,00 100,00 50,00 50,00 50,00 0,00 0,00 0,00 1942/43 1946/47 1950/51 1954/55 1958/59 1962/63 1966/67 1970/71 1974/75 1978/79 1982/83 1986/87 1990/91 1994/95 1998/99 2002/03 1955/56 1958/59 1961/62 1964/65 1967/68 1970/71 1973/74 1976/77 1979/80 1982/83 1985/86 1988/89 1991/92 1994/95 1997/98 2000/01 2003/04 1945/46 1949/50 1953/54 1957/58 1965/66 1969/70 1973/74 1977/78 1981/82 1985/86 1989/90 1993/94 1997/98 2001/02 AÑO AÑO AÑO
Yearly maximum 24 h rainfall Landslides damages direct observation Landslides damages from press information
11/65 Return periods for different rainfalls in nearest villages Southern Granada Province (Spain)
• Location >50 >60 >80 >100 >150mm / 24 h • • Albuñuelas 2 / 3 / 6 / 10 / >60 yrs. • Vélez Benaudalla 2 / 2.4 / 5 / 12 / >60 “ • Padul 5 / 12 /15 / >60/ >60 “ Return periods • Trevélez 1.2 / 1.1 / 3 / 5 / 15 “ • Cádiar 1.7 / 2 /10 / 30 / >60 “ • Lanjarón 2.2 / 3.3 /15 / 20 / 30 “
• Variable threshold in locations with similar geological and geomorphological features at close distances in the Guadalfeo River Valley
• In this region less than 10% of landslides were identified in time of occurrence and velocity regime and most occurred during the last event in 1996-97!!!
12/65 Fig.1. Geological domains in the Western Mediterranean (Sanz de Galdeano, 1994) 1.Foreland; 2.Neogene basins; 3.External Zones; a:Prebetic b: Subbetic c: Riphean. 4. Flysch units. 5. Internal Zones; a: Maláguide and dorsal; b: Alpujárride and Peridotites. c:Nevado-Filabride. 13/65 Lithological units
14/65 Active tectonics in the Betic Cordillera : main features • Moderate seismic hazard (basic acceleration <0.24g)
• Major faults with likelihood of large hyperhistorical earthquakes
• River overexcavation, continental uplift and active tectonics are correlated.
• Correlation between slope instability, landslide and active tectonics
Chacón, 1999; El Hamdouni et al, 2007 15/65 Expected earthquake horizontal slope accelerations for a return period of 500 year Antiseismic National Regulation NCSR-02. Chacón et al., 2007 16/65 This data are useful in landslide hazard assessment and mapping (in dynamic conditions) Historical record > 50 km depth Landslide triggering events
• Earthquakes Last 12 days
17/65 Historical record 10 to 50 km depth
18/65 Historical record, depth < 10 km
19/65 ESPON projects maps
Earthquake hazard
www.espon.eu
20/65 www.espon.eu
Historical recorded tsunami runups
In SW Spain, 1755´s Lisbon Earthquake gaves places to the only catastrophic tsunami known in historical times
This is not recorded in ESPON Project!!!
21/65 Landslide hazard in Europe
ESPON project
www.espon.eu
22/65 Geological setting
Andalucía (South Spain)
Central and Western Betic Cordillera
Tectonics, lithological units, earthquake activity
23/65 Landslides inventory
Andalucía (South Spain)
Central and Western Betic Cordillera
Types, distribution, main features, determinant and triggering factors, database, examples 24/65 Study area: Andalucia, South Spain
GROUP RN121-ENVIRONMENTAL RESEARCHES, NATURAL HAZARDS AND TERRAIN ENGINEERING
DEPARTMENT OF CIVIL ENGINEERING - UNIVERSITY OF GRANADA
Expected limit to cover at 1:400.000 and 8 pilot maps at 1:50.000 by 2008. Some few municipal maps at 1:5-10000 by 2009. Funds: Ministery of Science & 1980-2006 Education; Regional Govt. Provincial & Local 5949 landslide inventoried Administrations Susceptibility Maps at scales 1:200.000 to 1:5.000 Funds: Ministery of Science & 25/65 Education; Regional Govt. Rockfall Slide Flow TOTAL of events Landslide Inventory in SE Spain 1980-2006 1142 1639 3168 5949 ~4,5 landslides/km 2
Table 1. Areal distribution of landslides only in the Granada province (12.468 km2) Landslide Type (nº) Area (%) Accum.A.(%) Surface(km 2) 1 Rockfalls (990) 0.39 0.39 48.891 2 Slides (1527) 2.21 2.26 279.816 3 Earth & Mud flows (1302) 0.74 3.34 93.476 4 Debris flows (677) 0.39 3.73 49.838 5 Shallow slow mov. (410) 2.32 6.05 293.677 Total (4899 landslides, ) 6.05 765.698
• Abundance of landslide in mountain areas
• Natural triggering factors: flash rainfall storms, accumulated rainfall and earthquakes. Also bad land-use management and civil works
• Some “Dormant”, transient very slow active deep-seated landslides and many ephemeral shallow earth & mud flows or slide flow masses quickly erased by erosion or cultivation practices, also rockfall and slides. 26/65 Rock falls Slides Mud flows Debris flows Creep zones Complex movements 27/65 Mud flows Creep zones Complex movements
28/65 Landslide map of
Albuñuelas (Granada29/65 ) NW Guadalfero River Valley Central Guadalfeo River30/65 Valley Rockfall Slides Earth flow Debris flow 31/65 Fernández del Castillo, 2005 Landslide inventory, Low Guadalfeo River Valley Landslide database
32/65 Landslide Database
Betic Cordillera
Attributes
J.Chacón C.Irigaray T.Fernández R.El Hamdouni
J.Jiménez P.Fernández
33/65 Landslide inventory – Attributes Betic Cordillera
34/65 Detail of the landslide database, querrying and searching
35/65 Landslide types
Factor Rockfall Slide Earth& debrisflow Complex. All types Lithology AAABA Vegetation A B B C B Tectonic Unit A B B C B Slope AABBB Morphology A B A C B Vertical curvature B A A C B Channeldistance C A A A A Basinlimits C A B A B Channelsegments C A A C B Sloperoughness A C B C B Slopeamplitude C C A A B Geol. boundaries C C C A C Active tectonics indexes B A B A A
GIS correlation between factors and ruture typologies: A, B y C: high, medium and low correlation. Typologies:. CR.-DR : rockfalls; DesR.-T.: slides; F.T, earthflow; C.B. mudflow and CD : debris flow; MCPL: complex landslides.
Determinant factors for GIS susceptibility assessment A predominant, B frequent y C ocassional
36/65 Landslide triggering events
• Rainfall : meteorological data available since 1961
Five known rain periods: 1969-70, 1971-73, 1977-80, 1986-1988, 1996-97
Rainfall Irregularly distributed by basins and valleys, local effects predominate
In the Southern basins: only one widely destructive event is known: 1996-97
In the Guadalquivir river basin 2 only are widely identified: 1971, 1996
Not enough historical data for a systematic landslide hazard mapping in the whole region
It is possible to obtain enough information at local level for using in detailed scale hazard mapping of small areas
37/65 The inventory of landslides triggered by earthquakes is Triggering factors: very short: earthquakes It refers to landsliding effects during the 1755 (Lisbon) and 1884 earthquakes in Andalusia, both with magnitudes >6. Some few landslide triggered by these two events are the only references. Some few more are known at local sites. There not enough record of landslides triggered by landslides to support a systematic hazard mapping based on inventories. Methodologies based on geotechnical data, physical models or Newmark sliding block models are necessary to obtain
susceptibility maps for dynamic conditions38/65 Landslides Maps
Andalusia (South Spain)
Central and Western Betic Cordillera
Susceptibility, Hazard and Risk mapping
39/65 Types of Landslide preventive maps
• Based in spatial data ---- Susceptibiliy map
• Based in spatial and temporal data ---- Hazard map
• Based in spatial, temporal and consequences data --- Risk map
Chacón et al., 2006 40/65 INVENTORY SUSCEPTIBILITY EXPOSED ZONES rockfalls high high
Slides and flows middle middle low low
INVENTORY – DETERMINING FACTORS – TRIGGERING FACTORS – RETURN PERIODSQualitative – ELEMENT HazardAT RISK – VULNERABILITY Map Susceptibility Mapping Hazard Mapping Risk Mapping
GEOTECHNICAL DATA – SLOPE STAB MODELS SEISMIC HAZARD REGULATIONS
Landslides mapping using GIS. Chacón et al, 1992; 1993 41/65 Chacón et al, 1992, 1999; 2006 Landslide Risk Maps example in Periana (Varnes, 1984) area (Málaga)
(each element under each type of landslide hazard) Integrating all the spec. risks
ELEMENT VULNERABILITY AT RISK value very high SPECIFIC RISK TOTAL RISK high high high HIGH middle moderate moderate MODERATE poor low low LOW very poor very low very low VERY LOW
42/65 SZ: HIGH MODERATE LOW
reach
at rest
HZ: HIGH MOD /LOW
Landslides originate in high susceptibility zones and propagate down the slope to reach lower susceptibility zones.
Hazard zone propagates with the mass from the upper limit of the high susceptibility zone to the lower boundary of the mass at its rest slope angle.
Hazard depends also from mass and velocity : landslide destructive potential or intensity
The degree of development should be considered. Chacón et al., 1996 43/65 Landslide inventory: Scarp, rupture, deposit
If all rupture and deposit are considered together, the blue unit contributes with a 16%: it is susceptible!!
If just the green unit, as the only affected by the slope rupture, is considered the blue unit is not susceptible!!.
Only rupture surface should be considered for susceptibility assessment and mapping at large and middle scales
Head scarp 44/65 A statistical method fully developed in a GIS application
.1 . 2
GIS Matrix method (Irigaray, 1995; Degraff & Romesburg, 1980) 45/65 Scales and types of Susceptibility Maps developed in Andalusia .. • 1:400.000 to 1:10.000 - GIS Matrix method- validated both internally and externally
• 1: 10.000 to 1:2.000 geotechnical approaches: physical models ( both for statics and dynamic conditions ) or Rock Massif Classification systems (SMR)
46/65 Large scale susceptibility mapping in urban areas with geotechnical model planar failure-infinite slope 1:5.000
Several observations (planar failure in different slope head from which several earth flows developed and planar boundary underlying the slope 2 unit affected by creeping τ r c'+(σ n − Pw )⋅ tan ϕ' c'+(γ ⋅ d ⋅ cos i − Pw )⋅ tan ϕ' deformations) support the application FS = = = of a model of planar slide on infinite τ τ γ ⋅ d ⋅sin i ⋅ cos i slope (Taylor, 1948). Pw = γ w ⋅ hw
Safety Factor Susceptibility >1.2 Low EL Hamdouni et al, 1-1.2 Moderate 2006 47/65 < 1 High Linear mapping of rock cuts at detailed scale using the SMR index
Irigaray et al., 2003 48/65 Susceptibility Maps Guadalfeo River Valley (South Spain) 1: 20.000
Rockfalls Debris & Earth flows
Very low Very low Low Low Moderate Moderate High High Very High Very High
J.Jiménez, 2006 49/65 Susceptibility Maps Guadalfeo River Valley (South Spain) 1: 20.000
Slides (trans>rot) Complex landslides
Very low Very low Low Low Moderate Moderate High High Very High Very High
J.Jiménez, 2006 50/65 Integrated Landslide susceptibility map of the Guadalfeo River Valley (all ruptures) 1:20.000
Very low Low Moderate High Very High
J.Jiménez, 2006 51/65 52/65 Landslide susceptibility in urban areas of the Granada province (Chacón et al., 2006)
LOW
10 90 20 80 30 70 < 5000 5000-10000 40 60 10000-20000 50 50 20000-60000 60 40 > 60000 70 30 Granada province 80 20 90 10 MODERATE HIGH 10 20 30 40 50 60 70 80 90
Figure 3. Extension of landslide susceptibility classes in the 168 urban areas. Legend shows 53/65 the number of inhabitants (Granada capital: 238,292 inhab.) Landslide hazard and risk Preliminary qualitative hazard assessment in urban areas of Granada Province( Spain) Chacón et al. 2006 Qualitative classes of Destructive Potential of different types of landslides (DPL) depending of size and the expected dynamic behavior in the Granada province (Spain) m 3 SIZE Shallow very Earth & Mud Debris flow Rock fall Slide slow slope mov. flow
1 LOW MODERATE MO DERATE MODERATE SMALL VERY LOW 50 HIGH HIGH MIDDLE MODERATE HIGH HIG H 500 LARGE HIGH 5000 LOW VERY HIGH VERY LARGE VERY HIGH 50000 VERY HIGH EXT. LARGE MODERATE HIGH
54/65 Preliminary qualitative hazard assessment Landslide hazard and risk in urban areas of Granada Province( Spain) Chacón et al, 2006
Because of the lack of data about vulnerability of the element at risk, which at the scale 1:200,000 was simplified and considered uniform in every urban area.
Qualitative Landslide hazard classes by combination of landslide susceptibility and DPL
DPL SUSCEPTIBILITY
LOW MODERATE HIGH
Very low LOW MODERATE
Low MODERATE
Moderate HIGH
High HIGH Very high VERY HIGH
55/65 Chacón et al., 2006 Landslide hazard and risk
Figure 4. Landslide susceptibility maps in the village of Benalúa de las Villas (Granada) 56/65 An example of preliminary qualitative hazard assessm3.3. Landslideent of a givenhazard village. and risk
•Rock fall and debris flow are not expected to happen in this village.
•Shallow very slow slope movements: the available evidences show this hazard as low.
•Earth and mud flows: low, moderate or high hazards in the low, middle and high susceptibility zones in figure 4. Risk may also attain high level depending of size and speed of the mass.
•Slides: depending of the destructive potential of the expected slide, the resulting hazard may be between moderate to high.
Atlas of Natural Hazards of Granada Spanish Geological Survey – UGR – Provincial Council - 2006
General view of Benalúa de las Villas (Granada) 57/65 1353 inhabitants, elevation 828 m.a.s IAEG2006 Paper nº 414
Table 8. Distribution of the percentage of the land surface in each susceptibility class in urban areas with more than 10.000 inhabitants in the Granada province. (Census of 2004).
SUSCEPTIBILITY (%) LOCALITY (population) Low Moderate High ALBOLOTE (14.862) 95.8 4.2 0.0 ALMUÑECAR (23.073) 27.5 63.1 9.5 ARMILLA (16.938) 100.0 0.0 0.0 ATARFE (12.355) 99.0 1.0 0.0 BAZA (21.600) 82.8 1.8 15.4 GABIA GRANDE (10.400) 89.5 6.3 4.2 GRANADA (238.292) 89.8 9.1 1.1 GUADIX (20.035) 97.0 3.0 0.0 HUETOR-VEGA (10.362) 91.3 8.7 0.0 ILLORA (10.072) 72.2 15.8 12.0 LOJA (20.707) 70.0 26.6 3.5 MARACENA (17.232) 99.8 0.2 0.0 MOTRIL (55.078) 90.1 9.9 0.0 OGIJARES (11.324) 95.0 5.0 0.0 PINOS-PUENTE (13.303) 92.1 7.7 0.1 SALOBREÑA (11.420) 49.5 49.4 1.1 SANTA FE (13.803) 100.0 0.0 0.0 58/65 ZUBIA (LA) (15.312) 66.7 33.2 0.1 Despite all the limitations, preliminary qualitative specifics risk maps considering shallow landslides triggered by rainfall have been obtained
Elements of the territory Land use Water distribution system Urban Electric energy network Intensive farming Dams and reservoir Almond & olive trees Urban settlement and building Uncultivated Road Rural way Limit of basin
From the mentioned Map of Exposed Zones to shallow landslides (Qualitative Hazard) adding Elements of the territory classified in three levels of vulnerability we obtain Middle scale 59/65 Specific risk Maps for these sort of landslides Qualitative Specific Risk for rainfall triggered landslides in the Guadalfeo river J. Jiménez (2006): preliminary tool to priorize further large scale detailed maps 60/65 SPATIAL DATA SPATIAL AND TEMPORAL DATA . . Information layer SUSCEPTIBILITY HAZARD CONSEQUENCES (Specific & Total Risk)
basin or sub-basin scal, phys-mod o geotech (QL ) middle to (Qt) large scale (QL ) middle to (Qt) large scale
Landslide inventory………………….X……X……X……………… X………..X………………………..X…………X… (rupture & deposit)………………….. (X)….(X)……(X)………… X……… X………………………. X……….. X… by typologies…………………………(X)… (X)…. (X) ………… X……… X…………………..….. X……….. X… Tension cracks………………………(X).
Determinant Factor Analysis……….(X) ………………………… X………..X……………………….X………….X… (Unique condition GIS analysis ,uncertainty, neural or any other validated method of analysis of slope ruptures) SF value zoning………... ( X) …………………………………X……………………………………X….. RockMCS………………………………………….( X) …………………………..X……………………………………X……
Propagation (deposit reach, at rest, shadow angle)…………………………… (X)…… (X) ………………………..X………...... X Activity, Magnitud, Intensity……………………………………… (X)… …(X)………………………..X…………..X…. Triggering factor qualitative RP intervals……………………….. (X) …… (X) …………………… X…...... Triggering factors probability analysis……………………………(X)…… (X) ………………………..X… ………X….
Elements of territory qualitative values……………………………………………………………… (X)……… (X) Elements of territory quantitative assement……………………………………………………………(X)………… X Persons exposed analysis…………………………………………………………………...... (X)…………X Project management, warning system, ………………………………………………………………… X………….X Official Regulation Effects…………X…..X……X………………..X…………X………………………..X………….X
61/65 General methodology for landslide assessment and mapping Chacón et al, 2006 Convergence of proposal in Europe
62/65 Convergence in Landslide Susceptibility Mapping
National scales 1:1.000-000 heuristic, general stability conditions
Regional scale 1: 400.000 to 1:200.000 including inventory, slope and lithology
County scale 1.50.000 to 1:20.000 inventory and GIS correlation of factors
Large scale 1:10.000 to 1:5.000 using physical models, SMR, geotechnical data
63/65 FINAL REMARKS:
The future guidelines should be simple, short number of clear definitions of concepts, general methods and basic implications of the key points.
The inventory of landslide deposits and ruptures in Europe should be available soon
Landslide Susceptibility Map shows zones with similar amount of rupture and likelihood of new landslides:
A proposal of percentages of ruptures in susceptibility zones an d classes of hazard zones could be interesting for purposes of comparison of maps and regions
Qualitative hazard & risk assessment is acceptable when historical data are lacking
Also a vulnerability scale should be proposed for qualitative assessment
The appropriated scale of the map should be compatible with uses in each country:
1:200.000 1:50.000 1:25.000 1:10.000 1:5.000 ------European landslide inventory ------detailed inventories------susceptibility------hazard ------qualitative hazard and risk------
Seismic areas in Europe should be mapped for dynamic conditions: active faults should be identified and analysed 64/65 References
Chacón, J.; El Hamdouni, R.; Irigaray, C. and Fernández, T. (2006). Engineering geology maps: Landslides and GIS. Bulletin of Engineering Geology and the Environment. 65:341-411. Springer
Einstein, H.H.(1988). Special lecture: landslide risk assessment procedure. In Proceedings Vth ISL Lausanne, 2:1075-1090.
El Hamdouni, R. Irigaray, C. Fernández, T. Chacón, J. and Keller, E.A. (2007). Assessment of relative active tectonics, southwest border of the Sierra Nevada (Southern Spain). Geomorphology . (in press). On line doi : 10.1016/j.geomorph. 2007.08.004.
Fernández, P. Jiménez, J. El Hamdouni, R. Irigaray, C. M. Crosetto. y Chacón, J. (2006). Application of differential SAR interferometry to assessment of landslide activity in the Guadalfeo River Basin (Granada, Spain). 7 ª International Workshop on Geomatic. Institut Cartogràfic de Catalunya (ICC) , 15p.
Fernández, T. Irigaray, C. El Hamdouni, R. and Chacón, J. (2007). Correlation between natural slope angle and rock mass strength rating, Granada, Spain. Bulletin of Engineering Geology and the Environment. In press. Springer.
Irigaray, C.; Fernández, T.; El Hamdouni, R. and Chacón, J. (2007). Evaluation and validation of landslide- susceptibility maps obtained by a GIS matrix method: examples from the Betic Cordillera (southern Spain). Nat.Hazards , 41: 61-79. Springer Science+Business Media B.V.
Jiménez, J. Irigaray, C. El Hamdouni, R. Fernández, P. and Chacón, J.(2007). Building models for automatic landslide susceptibility analysis and mapping in ArcGIS. Geophysical Research Abstracts (GRA). 9. p: 04317.
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