Interventi di mitigazione del rischio da frana · Struttura della lezione Presentazione No.1...

Interventi di mitigazione

del rischio da frana

Università degli Studi di Salerno - Facoltà di Ingegneria – A.A. 2013-2014

Laurea Magistrale in Ingegneria per l’Ambiente ed il Territorio

Corso di Frane

Prof. ing. Michele Calvello

Struttura della lezione

Presentazione No.1

Landslide mitigation measures

LARAM School 2013, Session “Landslide risk management and mitigation”

Presentazione No.2

Landslide early warning systems: Rio de Janeiro case study

LARAM School 2013, Session “Landslide risk management and mitigation”

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University of Salerno (Italy) - Department of Civil Engineering

LARAM School 2013

International School on "LAndslide Risk Assessment and Mitigation"

2-14 September 2013, University of Salerno (Italy)

Prof. Michele Calvello

Landslide mitigation

measures

Main reference

SGI (2011). Deliverable 5.1

7th Framework Programme European Union Project SafeLand

Living with landslide risk in Europe: assessment, effects of global change, and risk management strategies

http://www.safeland-fp7.eu

Compendium of tested and innovative

structural, non-structural and risk-transfer

mitigation measures for different landslide types.

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Schematic classification of mitigation measures

Source: SGI (2011)

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Criteria for selection

Physical characteristics of the geosystem (e.g., stratigraphy, mechanical characteristics of

the materials, surface water and groundwater regime)

Morphology of the area

Actual or potential causative processes which can determine the occurrence of landslides

Phase and rate of movement at the time of implementation

Morphology of the area in relation to accessibility and safety of workers and the public

Environmental constraints (e.g. impact on archeological, hystorical and landscape value)

Preexisting structures and infrastructure that may be affected, directly or indirectly

Capital and operating cost, including maintenance

Source: SGI (2011)

Factors which determine the hazard

in terms of type, rate, depth and probability of occurrence of the landslide

Factors which affect the nature and quantification of risk for a given hazard

Presence and vulnerability of elements at risk (both in the potentially unstable area and in

areas which may be affected by the run-out)

Factors which affect the actual feasibility of specific mitigation measures

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Reduction of Hazard

1. Surface protection and control of surface erosion

2. Modifying the geometry and/or the mass distribution

3. Modifying the surface water regime – surface drainage

4. Modifying the groundwater regime – deep drainage

5. Modifying the mechanical characteristics of the unstable mass

6. Transfer of loads to more competent strata

7. Retaining structures

Landslide hazard mitigation measures

Source: SGI (2011)

R = H x E x V < RTOL

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Zoning to prevent development in hazardous areas or removing existing

development from hazardous areas (exclusionary zones)

Traffic restrictions (reduce number of vehicles)

Ambrozic et al. (2009)

Decreasing the number of vulnerable elements potentially affected by a landslide

Decreasing the probability that vulnerable elements will both spatially and

temporally intercept ground movements

Moving non-stationary vulnerable elements to less hazardous locations

Increasing awareness, detection and warning of hazards (either detected movement

or trigger conditions) and subsequent avoidance (evacuation or temporary

exclusion, followed by inspection before resuming normal use).

Reduction of Elements at risk

Particularly cost effective when the number of elements a risk is small in relation to

the extent of the landslide and of the affected area and when it is achieved through

the sustained implementation of appropriate long-term planning measures.

Ambrozic et al. (2009). Guidelines on relevant criteria to assess vulnerability and risk. FRANE Future Risk Assessment

as a New European approach to landslide hazards. European Commission, Directorate General Environment.


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Reduction of Vulnerability

Existing structures can be strengthened; for new structures, the potential effects of

impact from landslide material can be taken into account from the outset. This

approach is typically applicable only in relation to relatively shallow slides and is not

applicable to withstand the impact form very large landslides.

Landslide vulnerability (passive) measures

Increase the resistance of elements at risk

Stop or deviate the path of the landslide

Works can be carried out to intercept and block or at least to deviate or to slow down

the sliding materials. This type of works relates mainly to the fall of massive blocks

or to flows of all types.


Source: SGI (2011)

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Share residual risk

Increase the tolerance towards the residual risk after implementing all other

(technically and economically) possible mitigation measures.

Voluntary or compulsory insurance

(share the risk among a large number of people)

Public Authorithy takes on the same general role of managing shared risk as the

insurance company.

Compulsory systems based on taxes and public intervention

Owners can tolerate a higher level of residual risk, since any damage that may occur

would be refunded by the insurance company. Clearly, this strategy is useful

especially when the elements at risk consist mainly of facilities and properties, which

normally corresponds to the reactivation of slow or very slow movement.

Two levels

of operation


Source: SGI (2011)

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Share residual risk

Natural disaster insurance specificities for Fire and Natural hazards


Zimmerli (2003)

Zimmerli P. (2003). Natural catastrophes and reinsurance. Tech. Rep., SwissRe.

http://media.swissre.com/documents/Nat_Cat_reins_en.pdf

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Reduction of Hazard - 1

Erosion control

Source: SGI (2011)

Aerial Hydroseeding (http://www.ericksonaircrane.com/hydroseeding.php)

Typical drawing: Erosion Control Blankets for soil slope stabilization (http://www.urbancreeks.org/Erosion%20Control%20Blankets.pdf)

Live fascine structure (www.nrcs.usda.gov/technical/stream_restoration)

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Erosion control

Source: SGI (2011)

Some influences of vegetation on the soil. (source: Coppin and Richards, 1990)

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Modifying slope geometry

Source: SGI (2011)

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1. REMOVAL OF (ACTUAL OR POTENTIALLY) UNSTABLE SOIL/ROCK MASS

2. REMOVAL OF LOOSE OR POTENTIALLY UNSTABLE

BLOCKS/BOULDERS (TRIMMING AND SCALING)

With rope access

(http://pacificblasting.com/stabilization.html)

By long reach equipment

(Highland and Bobrowski, 2008)

3. REMOVAL OF MATERIAL FROM DRIVING AREA

Remedial works for Settebagni slide included major reprofiling from the original 1960’s cut slope profile

(SGI-MI project files)

Source: SGI (2011)

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Rating on a scale 1 to 10 (the higher the grade, the most suitable the method). Zero rating means «not applicable»

Modifying slope geometry > Removal of mass

1 3 2 Applicability (rating of methods)

Source: SGI (2011)

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4. SUBSTITUTION OF MATERIAL IN DRIVING AREA WITH LIGHTWEIGTH FILL

5. ADDITION OF MATERIAL TO THE AREA

MAINTAINING STABILITY

Use of shredde tyres for lanslide remediation (Dubreucq and Pezas, 2009) Installation of expanded

clay for lanslide

remediation

(Di Prisco, 2007)

Stabilization of Tablachaca Dam Landslide, Peru, crossection (Millet et al., 1992)

Source: SGI (2011)

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Modifying slope geometry > Substitution or addition of material

4 5 Applicability (rating of methods)

Source: SGI (2011)


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Modifying the surface water regime

1. SURFACE DRAINAGE WORKS (DITCHES, CHANNELS, PIPEWORK)

Source: SGI (2011)

2. LOCAL REGRADING TO FACILITATE RUN-OFF

Open ditch lined with pitched stone, Gimillan nr. Cogne (AO), Italy

(photo: G. Vaciago, SGI-MI)

Typical detailing of open ditches

(www.co.nrcs.usda.gov)

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Modifying the surface water regime > Facilitate run-off


Source: SGI (2011)


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Source: SGI (2011)

3. SEALING TENSION CRACKS

4. IMPERMEABILIZATION (GEOMEMBRANES, IMPERVIOUS FACING)

Typical detail

Tension cracks, 2009 reactivation

Petacciato Landslide, Italy

(source: SGI-MI Project files)

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Modifying the surface water regime > Impermeabilization


Source: SGI (2011)


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Modifying the surface water regime > Vegetation

5 Applicability (rating of methods)

Source: SGI (2011)


VEGETATION – HYDROLOGICAL EFFECTS

Wu (1995)

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Source: SGI (2011)

6. HYDRAULIC CONTROL WORKS (CHANNEL LINING AND CHECK DAMS)

Pitched stone channel lining and concrete check

dams, Gimillan, nr. Cogne (AO), Italy

(photo: G. Vaciago, SGI-MI)

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Source: SGI (2011)

7. DIVERSION CHANNELS

Examples of landslide dam break and flood prevention through diversion channel

(Schuster, 2006; Liu et al., 2010)

Mechanism and consequences

of landslide dams

(www.kingston.ac.uk)

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Modifying the surface water regime > Hydraulic works and diversion channels


Source: SGI (2011)


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Modifying the groundwater regime

1. SHALLOW TRENCHES FILLED WITH FREE-DRAINING MATERIAL

Source: SGI (2011)

2. DEEP TRENCHES FILLED WITH FREE-DRAINING MATERIAL

Shallow trenches with only main

branches: a) Plan, b) Cross

section.

Shallow trenches, with main

and secondary

branches: c) Plan, d)

Longitudinal section

(Urciuoli, 2008).

Examples of shallow trenches. The upper part

of the system is covered by stones in order to

lower the environmental impact.

Deep trenches with only main

branches: a) Plan, b) Cross section.

Deep trenches, with main and

secondary branches:

c) Plan, d) Longitudinal section

(Urciuoli, 2008)

Construction of deep drainage

trench by secant piles technique:

a) first series of piles; b) odd-

numbered piles

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Modifying the groundwater regime > Trenches


Source: SGI (2011)


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Source: SGI (2011)

3. SUB-HORIZONTAL DRAINS

(CONVENTIONAL DRILLING)

4. SUB-HORIZONTAL DRAINS

(DIRECTIONAL DRILLING)

The phases of HDD construction:

a) drilling the pilot hole,

b) reaming of the pilot hole,

c) pipe string pull - back.

Phases of construction of sub-horizontal drains

Pipe lines

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Modifying the groundwater regime > Drains


Source: SGI (2011)


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Source: SGI (2011)

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Source: SGI (2011)

5.1.2.. VERTICAL SMALL DIAMETER (<800mm)

WELLS – UNDERDRAINAGE OF PERCHED ACQUIFER

5.1.1. VERTICAL SMALL DIAMETER (<800mm)

WELLS –RELIEF OF ARTESIAN PRESSURE

Typical relief well in a confined acquifer with the piezometric level

higher a) and lower b) than the groundsurface

Example of well to underdrain the perched table

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Source: SGI (2011)

5.1.4. VERTICAL SMALL DIAMETER (<800 mm) WELLS – SIPHONING

5.1.3. VERTICAL SMALL DIAMETER (<800mm) WELLS – PUMPS

Section showing well and siphon installation

(source: WJ Groundwater Ltd)

Examples of

a) well point system

b) educator system

c) submersible pump system

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Modifying the groundwater regime > Small diameter wells

5.1.1 5.1.3 5.1.4 5.1.2 Applicability (rating of methods)

Source: SGI (2011)


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Source: SGI (2011)

5.3. VERTICAL LARGE DIAMETER (>2000mm)

WELLS – GRAVITY DRAINAGE THROUGH BASE CONDUCTOR

5.2 VERTICAL MEDIUM DIAMETER (1200-1500mm)

WELLS- GRAVITY DRAINAGE THROUGH BASE CONDUCTOR

Shematic longitudinal section of an array of medium diameter wells

(Leoni et al. 2003)

Typical structural well section and machinery to

construct the borehole for PVC pipes

(Leoni et al., 2003)

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Source: SGI (2011)

5.4. CAISSON (> 5-6 m), WITH GRAVITY DRAINAGE

(AND SECONDARY SUBHORIZONTAL DRAINS)

Vertical

Section

Typical large diameter caisson with drainage function

(source: SGI-MI project files)

Horizontal

Section

Well with secondary drainage;

structure consists of discrete piles

and concrete ribs

(source (SGI-MI project file

Detail of microdrain heads

(source (SGI-MI project file

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Modifying the groundwater regime > Large diameter wells

5.2 5.3 5.4 Applicability (rating of methods)

Source: SGI (2011)


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Modifying the groundwater regime > Drainage tunnels and galleries


Source: SGI (2011)

6. DRAINAGE TUNNELS, ADITS, GALLERIES, WITH

SECONDARY DRAINS OR AS OUTLET FOR WELLS


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Modifying the mechanical characteristics of the unstable mass > Vegetation


Source: SGI (2011)

Selected species can develop

significant root systems

(source www.pratiarmati.it)

VEGETATION – MECHANICAL EFFECTS

Wu (1995)

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Modifying the mechanical characteristics of the unstable mass > Substitution


SUBSTITUTION

Source: SGI (2011)

Substitution of failed soil mass by excavation and recompaction

(Rogers., 1992)

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Modifying the mechanical characteristics of the unstable mass

3. COMPACTION FROM SURFACE 4. DEEP COMPACTION

VIBROCOMPACTION

VIBROREPLACEMENT

VIBRODISPLACEMENT

Source: SGI (2011)

Mechanism and consequences

of landslide dams

(www.kingston.ac.uk)

www.vibroflotation-ng.com



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Modifying the mechanical characteristics of the unstable mass > Compaction

3 Applicability (rating of methods) 4

Source: SGI (2011)

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5. MECHANICAL DEEP MIXING WITH LIME AND/OR CEMENT

6. LOW PRESSURE GROUTING WITH CEMENTITIOUS

OR CHEMICAL BINDER

7. JET GROUTING

Source: SGI (2011)

Principle of deep soil mixing, here; dry soil mixing (McCarthy, 2007)

Detail of cutter/mixer drums

(source: Soletanche Bachy)

Conceptual diagram of permeation grouting

(Andrus and Chung,1995)

Left: Principles of jet grouting Right: The three basic systems of jet grouting (Nikbakhtan et al., 2010)

Large soilcrete columns can be formed in

favourable conditions (Shibazaki, 2003)

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Modifying the mechanical characteristics of the unstable mass > Deep mixing and grouting

5 Applicability (rating of methods) 6 7

Source: SGI (2011)

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MODIFICATION OF GROUNDWATER CHEMISTRY

(E.G. LIME PILES)

Although some experimental case histories are

reported in the literature, some of which

characterized by a reasonable degree of

success, there is no consolidated and reliable

design approach at this stage for landslide

stabilization based on modifications of

groundwater chemistry, which at present

remains wholly empirical.

Source: SGI (2011)

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Transfer of load to more competent strata

1. COUNTERFORT DRAINS (TRENCH DRAINS

INTERSECTING BASAL SHEAR PLANE)

2. PILES

3. BARRETTES (DIAPHRAGM WALLS)

4. CAISSONS – MECHANICAL EFFECTS

Source: SGI (2011)

Counterfort drains provide additional stabilization by

intercepting the slip plane (Carter, 1992)

Schematic section and layout

(source: SGI-MI project files) Kelly operated grab for excavation

of barrettes and diaphragm walls


Schematic plan and section


Typical layout of structural caissons

equipped with active strand anchors


Caisson top - chamber for the

inspection of strand anchor heads


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1 3 4 2 Applicability (rating of methods)

Transfer of load to more competent strata > Piles, diaphragms and caissons

Source: SGI (2011)

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Transfer of load to more competent strata

5. SOIL NAILING

6. DOWELS AND HARNESSING

7. ROCK BOLTING

8. STRAND ANCHORS

Source: SGI (2011)

Cut away view of typical multistrand tendon (Sabatini et al., 1999)

Dowels to stabilize specific blocks above an existing railway (source: SGI-MI project files)

Nailing on debris slope using nails grouted in predrilled holes; note associated

wire mesh and biotechnical facing (source: SGI project files)

Schematic detail (source: SGI-MI project files)

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5 7 8 6 Applicability (rating of methods)

Transfer of load to more competent strata > Nails and anchors

Source: SGI (2011)

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Retaining structures

1. REINFORCED SOIL STRUCTURES

2. GABION WALLS

3. CRIB WALLS

4. DRYSTACK MASONRY WALLS

5. MASS CONCRETE OR MASONRY WALLS

6. REINFORCED CONCRETE STEM WALLS

Source: SGI (2011)

Types of reinforced soil wall facing

(after Wu, 1994, as reported by Berg et al., 2009)

Tipical application of gabion walls

(source www.gabbioni.it)

(Chapman et al., 2000)

(Chapman et al., 2000)

Typical in-situ r.c. stem wall

(source: www.mailingmaggioli.it))

Stone masonry retaining walls at Machu Pichu

(source: www.travel.webshot.com)

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1 3 4 5 6 2 Applicability (rating of methods)

Retaining structures

Source: SGI (2011)

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Toolbox on the web

SGI (2011). Deliverable 5.2




Toolbox of landslide mitigation measures

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Toolbox on the web

http://sltoolbox.ngi.no/default.aspx

Based on the compendium of mitigation measures produced in

Deliverable D5.1 “Compendium of tested and innovative

structural, non-structural and risk-transfer mitigation measures for

different landslide types” a toolbox was developed for an easy,

intuitive, operational and user-friendly system to assist decision-

making and to guide the user in the choice of the most appropriate

mitigation measures.

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Current web address

University of Salerno (Italy) - Department of Civil Engineering

LARAM School 2013

International School on "LAndslide Risk Assessment and Mitigation"

2-14 September 2013, University of Salerno (Italy)

Prof. Michele Calvello

Landslide early warning systems:

Rio de Janeiro case study

Early warning systems: a definition

UNISDR (2009)

The set of capacities needed to generate and disseminate

timely and meaningful warning information to enable

individuals, communities and organizations threatened by a

hazard to prepare and to act appropriately and in sufficient

time to reduce the possibility of harm or loss.

UNISDR (2009). ISDR: Terminology. http://www.unisdr.org/eng/library/lib-terminology-eng%20home.htm

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UNISDR (2009)

UNISDR (2009). ISDR: Terminology. http://www.unisdr.org/eng/library/lib-terminology-eng%20home.htm

UNISDR (2006). Developing Early Warning Systems: A Key Checklist. http://www.unisdr.org/2006/ppew/info-resources/ewc3/Checklist-english.pdf

A people-centred early warning system necessarily comprises four key elements

Knowledge of the risks

Monitoring, analysis and

forecasting of the hazards

Communication or dissemination

of alerts and warnings

Local capabilities to respond to

the warnings received

Early warning systems: a definition

UNISDR (2006)

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Di Biagio and Kjekstad (2007)

Landslide early warning systems: elements and activities

Di Biagio &, Kjekstad (2007). EarlyWarning, Instrumentation and Monitoring Landslides.

2nd Regional Training Course - Asian Program for Regional Capacity Enhancementfor Landslide Impact Mitigation (RECLAIMPhase II)

Four main activities

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Bell et al. (2009)


Bell et al. (2009). Integrative Frühwarnsysteme für Gravitative Massenbewegungen (ILEWS). Monitoring, Modellierung, Implementierung. Klartext Verlag, Essen.

[retreived from: Thiebes B. (2011). Landslide analysis and early warning - Local and regional case study in the Swabian Alb, Germany. PhD Thesis, Universitat Wien]

ILEWS project (Integrative Landslide Early Warning Systems)

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Intrieri et al. (2013). Brief communication “Landslide Early Warning System: toolbox and general concepts".

Nat. Hazards Earth Syst. Sci., 13:85–90. doi:10.5194/nhess-13-85-2013

Intrieri et al. (2013)

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ICG (2012). Deliverable 4.8




Guidelines for landslide monitoring and early warning

systems in Europe – Design and required technology.

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The scale issue

“[…] the report focuses on site-specific

EWS on a local scale.”

CMCC (2011). Deliverable 4.2

Short-term weather forecasting for prediction of

triggering of shallow landslides. Methodology, evaluation

of technologies and validation at selected test sites.

“For shallow landslides triggered by meteorological

events, it is necessary to design and to develop simulation

models able to produce regional warning maps.”

The scale issue

Areal extent of system operation

Landslide early warning systems can be installed for…

Single slopes

(LOCAL system)

Massifs, Large areas, Regions, States

(REGIONAL system)

Intrieri et al. (2102)

Intrieri et al. (2102). Design and implementation of a landslide early warning system. Engineering Geology, 147–148:124–136.

Baum and Godt (2010). Early warning of rainfall-induced shallow landslides and debris flow in the USA. Landslides, 7:259–272.

Baum and Godt (2010)

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Landslide Early Warning strategy in Rio de Janeiro (Brazil)

A two tier system…

ALERTA-RIO

A2C2 “Sistema de Alerta e Alarme Comunitário para Chuvas Fortes”

Officially created in 1996 by the GEO-RIO Foundation with the objective of issuing alert

bulletins, warning the populations for severe weather conditions which may induce flash floods

or landslides within areas of the city.

Operational 24 hours a day, seven days a week, with a staff of meteorologists, geologists,

engineers and technical-level personnel (only maintenance of the equipment is outsourced)

From 2010 it operates from the multipurpose Municipal Operations Center (CO-Rio)

Currently deployed in 103 “informal communities” (i.e. favelas) of the city

Based on few essential elements, some of which shared with ALERTA-RIO: risk zoning;

rainfall model and thresholds for early-warning; local and continuous measurement of rainfall;

timely rainfall prediction; apparatus for alert delivery (i.e. sirens); definition and

implementation of evacuation procedures; education and training of the population.

Not designed to be permanent, as the sirens are supposed to be uninstalled from communities

when, as it is planned, the risk will be lowered to acceptable levels either through stabilization

works or by the removal of dwellings (depending on results from cost-benefit analyses)

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Landslide Early Warning strategy in Rio de Janeiro (Brazil) > ALERTA RIO

d’Orsi et al. (1997)

Type and levels of alert

LANDSLIDE ALERT (PROBABILIDADE DE ESCORREGAMENTO)

based on measured rainfall

RAINFALL ALERT (CONDICAO DE CHUVAS)

based on rainfall forecasts

d’Orsi et al. (2007). Rio-Watch: The Rio de Janeiro landslide watch system. 2nd Pan-Am Symp. Landslides, Rio de Janeiro, 1:21-30.

d’O

rsi e

t a

l. (1

99

7)

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Pluviometers: location


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Pluviometers: areas of influence


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Zones of alert

Baia de Guanabara

Jacarepaguà

Baia de Sepetiba

Zona Sul


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Thresholds for levels of alert

RA

INF

AL

L

LA

ND

SL

IDE

S

«ALERTA»


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ALERTA

ALERTA

Image: g1.globo.com

The “alert procedure”


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On the internet

http://www0.rio.rj.gov.br/alertario/


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On the internet


Rainfall annual reports


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Landslide annual reports On the internet


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Some preliminary analyses on

landslides and alerts…


Datasets by:

GEO-RIO

Analyses by:

Luca Piciullo

(PhD student,

University of Salerno)

Year 2010

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A recent example: 17 May 2013, 6 pm

Rainfall alert level in the four zones


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Landslide alert level in the four zones


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Landslide alert level in the four zones

Areas of influence

of pluviometers


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Landslide risk zoning of Rio de Janeiro’s “communities”, i.e. favelas (Geo-Rio, 2010)

117 communities

with houses inside

high landslide risk areas

Levels of landslide risk

• High

• Medium

• Low

A2C2 system installed

(between 2011 and 2012)

in 103 communities

Landslide Early Warning strategy in Rio de Janeiro (Brazil) > A2C2

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166 alarm stations

http://websirene.rio.rj.gov.br/portal/portal

86 sirens

with pluviometers

80 sirens


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The “alert and alarm procedure”

Alert…

…and Alarm

Source: Rio Prefeitura (2012). Plano de contingencia – verao 2012/2103.

http://www.formulariosonline.com.br/sitedc/index.php?option=com_content&view=article&id=109&Itemid=65

Rainfall Threshold

1 h 40 mm/h

24 h 125 mm/24h (> 6 mm/h)

96 h 200 mm/96h (> 40 mm/24h)


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Implementation of the system: information strategy

Source: Rio Prefeitura (2012). Plano de contingencia – verao 2012/2103.

Posters and leaflets

Calendars

Cartoons

Simulations of evacuation


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Implementation of the system: simulations of evacuation

Source: Rio Prefeitura (2012). Roteiro de implementacao do A2C2.


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24 h threshold

…the

alert

was

not

given

(in this

case).


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On the internet

http://www.formulariosonline.com.br/sitedc/index.php?option=com_content&view=article&id=89&Itemid=61


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Interventi di mitigazione del rischio da frana · Struttura della lezione Presentazione No.1...

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Transcript of Interventi di mitigazione del rischio da frana · Struttura della lezione Presentazione No.1...