Analysis of the potential effects of dam break flooding ...€¦ · Mirko Baruffini, Maurizio Pozzoni and Roberto Marzocchi Institute of Earth Sciences, University of Applied Sciences

1

DACD – Dipartimento ambiente costruzioni e designIST – Istituto scienze della Terra

Analysis of the potential effects of dam break flooding using a GIS-tool for risk assessment in mountain regions.mountain regions.An exploratory study on an hypothetical event: the Val Canaria flood.

Mirko Baruffini, Maurizio Pozzoni and Roberto MarzocchiInstitute of Earth Sciences, University of Applied Sciences of Southern Switzerland,IST-SUPSI, Campus Trevano, CH-6952 Canobbio ([email protected])

23.09.2011

Contents2Analysis of the potential effects of dam break flooding using a GIS-tool for risk assessment in mountain regions

Contents

oo Fieldwork and data analysisFieldwork and data analysis

oo Hazard zoning and landslidesHazard zoning and landslides

oo Flooding ModelsFlooding Modelsoo Flooding ModelsFlooding Models

•• FLOFLO--2D2D

•• R.DAMFLOOD R.DAMFLOOD

oo Risk analysis methodologyRisk analysis methodology

•• RRiskisk Assessment tool in Assessment tool in ArcGISArcGIS®®

•• Results and considerationsResults and considerations

oo Conclusions and next stepsConclusions and next steps

oo ReferencesReferences

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oo ReferencesReferences

Fieldwork and data analysis (1)3Analysis of the potential effects of dam break flooding using a GIS-tool for risk assessment in mountain regions

Fieldwork and data analysis (1) Geographical setting

Canaria valley is located in Northern Tessin, close to the St. Gotthard Alps corridor: a very

important area for road and rail connections between North and South Europe.

MontiMonti

Rutan dei SassiRutan dei Sassi FöiscFöisc Prato di CèPrato di Cè

Transport infrastructures: M dM d

─ Highway─ Main road─ Railway

Transport infrastructures:

AiroloAirolo

MadranoMadrano

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─ Railway


Fieldwork and data analysis (2)Because of its particular geological setting the entire region is affected by numerous types of landslides Val Canaria landslides consist of failed rock masses on both sides of the valley withlandslides. Val Canaria landslides consist of failed rock masses on both sides of the valley with a total volume of about 80 million m3. The area is historically known for its instabilityPresented in session B1 – Previsione e monitoraggio frana: September 23rd, 15:45

.

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5Analysis of the potential effects of dam break flooding using a GIS-tool for risk assessment in mountain regions

Fieldwork and data analysis (3)Main recent events:o 2007: a mass of 40’000 m3 fell and arrived close to the river without consequences

Fieldwork and data analysis (3)

o 2007: a mass of 40 000 m fell and arrived close to the river without consequenceso 2009: a mass of 350’000 m3 collapsed; the deposit reached the river and destroyed the nearby roado 2010: landslide deposit + river debris generated a temporary dam that collapsed destroying the road and some cottageso 2011: river debris destroying the road and some cottages

Th h l f th C i t t thThe channel of the Canaria stream at the slope’s toe is filled with unvegetatedlandslide debris.

A natural dam could form after a landslide event with a possible subsequent disastrous failure and destructive consequences on thedestructive consequences on the important traffic lines passing in the Leventina valley.

23.09.2011 The complex slide of Oct. 2009


Fieldwork and data analysis (4)The dam break scenario, although characterized by a very low probability of occurrence, is nevertheless possible and could have effects on downstream infrastructure

A damaged infrastructure would i t i l d th t

nevertheless possible and could have effects on downstream infrastructure

Mud and debris on a stretch of motorway in Ticino

cause serious material damage that would require extraordinary repairs or restorations. The services inactivity, as a result of a malfunction, would

y

as a result of a malfunction, would generate important financial losses and problems in essential services supply in the region (Maggi R. et al, 2009)2009).

Risk analysis of this scenario

23.09.2011Motorway chaos after the landslide occurred in Giornico August 29, 2003


Hazard assessment (1)Hazard assessment (1) Identification of the natural hazards

o Identification of the threatening elements: landslides, rock falls, debris flows, snowavalanches, etc. This is based on the analysis of previous studies and can becompleted by regional studies aerial photo imagery field surveys historical datacompleted by regional studies, aerial photo imagery, field surveys, historical dataanalysis and environmental models.

o The resulting products are maps of natural hazard phenomena, which identify areasg p p p , ywhich are prone to the various natural hazards.

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Hazard assessment (2)Hazard assessment (2) Estimation of the hazard level

o The natural hazards that have been identified can be

attributed with their degree of hazard, specifying howSwiss Hazard matrix

dangerous a certain situation is.

o Two main aspects lead to a description of the level of

hazard:

o How often a hazard occurs Return period

o With what intensity (the magnitude of the event)

o The combination of these 2 parameters, following the

Swiss Federal Guidelines (OFAT, OFEE, OFEFP,

1997), lead to the hazard matrix

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Hazard assessment (3)Hazard assessment (3)Estimation of the intensityThe intensity is a description of the magnitude of an event and is divided into three classes:

high, medium and low intensity.

23.09.2011 Tab. 1


Flooding Models (1)Flooding Models (1)FLO-2D

oo 22--D physical process model D physical process model oo Conserves volume and reports on itConserves volume and reports on itoo Combined hydrologic and hydraulic modelCombined hydrologic and hydraulic modeloo Unconfined flooding with no boundary conditions or hot startsUnconfined flooding with no boundary conditions or hot startsoo Routes entire hydrographRoutes entire hydrographoo Variable Variable timestepstimesteps enable fast simulationsenable fast simulations

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Flooding Models (2)Flooding Models (2)R.DAMFLOODo GRASS-GIS module, which aim is to provide a 2D GIS-embedded hydraulic numerical model for the dam break flooding (presented in session S2(presented in session S2 –– GeomaticaGeomatica: September 23rd, : September 23rd, 15:45)15:45)o Developed in recent years (Marzocchi and Cannata 2009; Cannata and Marzocchi 2011)o Developed in recent years (Marzocchi and Cannata, 2009; Cannata and Marzocchi 2011) by the Institute of Earth Sciences (SUPSI)o Based on the on the numerical solution of the Shallow Water Equations (SWE) using a Finite Volume Method (FVM).

Giving as input a Digital Terrain Model (DTM), the Giving as input a Digital Terrain Model (DTM), the initial water depth, the breach geometry and the initial water depth, the breach geometry and the p , g yp , g ymanning roughness coefficient it give several output manning roughness coefficient it give several output (maximum water depth, velocity and intensity, time (maximum water depth, velocity and intensity, time of occurrence, etc.) that can be directly used for the of occurrence, etc.) that can be directly used for the h d th d thazard assessment. hazard assessment.

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Flooding Models (3)Flooding Models (3)Model and work objective

o Model the potential flooding (due to the breaking of the natural dam), to predict

inundation areas in the upper Leventina valley, with a particular attention to the

highway route.

o Evaluation of the two models was performed by comparing simulation results

against each other, with the aid of a GIS.

Landslide model resultLandslide model result Localization of the natural dam

200 m200 m

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200 m200 m


Flooding Models (4)Flooding Models (4)Model reference scenarios - Dam featuresoo Different types of scenarios, with dam height vary form 15 to 35 metersDifferent types of scenarios, with dam height vary form 15 to 35 meters

oo Reference scenario: dam maximum height of about 30 mReference scenario: dam maximum height of about 30 m,, according to the results according to the results

of a landslide scenario, modeled with MassMov2D (presented in session S2of a landslide scenario, modeled with MassMov2D (presented in session S2 ––

GeomaticaGeomatica: September 23rd, 15:30): September 23rd, 15:30)

oo 2 types of breaching the dam, without taking consideration of debris flow (next 2 types of breaching the dam, without taking consideration of debris flow (next

step)step)

Scenario Floodingmodel

Number of failure element (8x8m)

Dam elevation [m]

Dam maximum height [m]

Water volume [m3]

1-FLO 2D FLO 2D 3 1’350 31 247’000O O 3 350 3 000

2-FLO 2D FLO 2D 4 1’350 31 247’000

1-R.DAMFLOOD r.damflood 3 1’350 31 248’550

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2-R.DAMFLOOD r.damflood 4 1’350 31 248’550

Tab. 2


Flooding Models (5)Flooding Models (5)Comparison of model resultsoo Good agreement between the 2 models: first crossGood agreement between the 2 models: first cross--validation of R.DAMFLOODvalidation of R.DAMFLOOD

oo Main differences due to different methods of dam breakMain differences due to different methods of dam break

FLOFLO--2D2D R.DAMFLOODR.DAMFLOOD

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Flooding Models (6)Flooding Models (6)From model results to the hazard map (FLO-2D)

Combining flow depth and flow velocity map, we obtain the Combining flow depth and flow velocity map, we obtain the intensity map (for a given return period) and then the hazard map.intensity map (for a given return period) and then the hazard map.The operation could be done directly in FloThe operation could be done directly in Flo--2D or exporting model 2D or exporting model output inoutput in ArcGISArcGISoutput in output in ArcGISArcGIS

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Risk analysis methodology (1)Risk analysis methodology (1)BUWAL recommendations

Three stages may be appliedQUALITATIVE: protection deficit Three stages may be applied

individually according to the analytical depth required.

p

Together, however, they form a unit.

QUANTITATIVE: global values

The stages from 1 to 3 are increasing in analysisincreasing in analysis resolution and data requirements.

QUANTITATIVE: object values

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Risk analysis methodology (2)Risk analysis methodology (2)Risk Assessment tool in ArcGIS® o The tool allows studying the risks deriving from natural

hazards along transportation corridors.

The tool organizes the various data and calculates theo The tool organizes the various data and calculates the

quantitative object and collective risks (BUWAL, 1999),

quoted in relation to persons (number of fatalities) and q p ( )

material assets (property damage in Swiss Francs).

Simulation environment developed within ArcObjects theo Simulation environment developed within ArcObjects, thedevelopment platform for ArcGISo The topic of ArcObjects usually emerges when users realizethat programming ArcObjects can actually reduce the amount ofp g g j yrepetitive work, streamline the workflow, and even producefunctionalities that are not easily available.o in ArcGIS. We have adopted Visual Basic for Applications(VBA) for programming ArcObjects because VBA is already

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(VBA) for programming ArcObjects, because VBA is alreadyembedded within ArcMap and ArcCatalog.


Risk analysis methodology (3)Risk analysis methodology (3) Risk Assessment tool in ArcGIS®

2 Ri k l i i l d

1 - Risk analysis: data recording and import Just click a button!

2 - Risk analysis: a numerical procedure

23.09.20113 - Risk analysis: visualisation of the results


Risk analysis methodology (4)Risk analysis methodology (4)Result of the analysisThe quantitative analysis based on investigations specific to the object according to BUWAL

(1999) can be performed using Risk Assessment tool in ArcGIS® on purpose developed.

Ri k l i tScenario 1Scenario 1

Hazard Level

Risk analysis parameters:

Hazard type Flooding

Return period (1/he) [yrs] 300

A2-Highwaymedium

high

low

Return period (1/he) [yrs] 300

Object type Highway

Velocity (v) [km/h] 90low

Daily Traffic (DTV) [nb of auto] 16.500Vehicle occupancy (β) [people/auto)] 1,59

L th lit (λ) 10 8

Hazard zonecollective risk

Lethality (λ) 10-8

Tab. 3

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****

** gfv

DTVphr raeij

Yearfatalities ofNumber

Hazard zone


Risk analysis methodology (5)Risk analysis methodology (5)Discussion and conclusiono The risk analysis gives for all the four scenarios a numerical results which is <0.0001

number of fatalities/year.

o This is due to:

the low value of lethality considered, the lethality is higher if we consider another type

f i k (d b i fl ) d if h hi h i t itof risk (debris flow), and if we have an high intensity.

the limited dimension of the object at risk with medium intensity

the high value (300 years) of the return period of the considered events.g ( y ) p

Scenario Intensity Length (g ) [m] Risk [Death/year]

1 FLO 2D Medium/Low 193 <0 00011-FLO 2D Medium/Low 193 <0.00012-FLO 2D Medium/Low 194 <0.00011-R.DAMFLOOD Low 193 <0.00012 R DAMFLOOD L 194 <0 0001

23.09.2011Tab. 4

2-R.DAMFLOOD Low 194 <0.0001


Conclusion and next steps

o Good agreement between the 2 flooding models

Conclusion and next steps

o Better knowledge of potentialities and limits of the 2 modelso Obtain an overview of the interests and the need to act to reduce vulnerability and the hazardous nature of the Gotthard corridor.o The lack of protection of identified risk is an useful indicator to plan for risk reduction measures.o It is possible to limit the vulnerability with protection measures referred particularly to sensitive objects. Another possibility is to limit the danger of the corridor with measures that restrict the probability of occurrence of a hazard.

NEXT STEPSo Perform a simulation with FLO-2D considering the debris flow option and consequently re-evaluate the risk.o Further tests and improvement in the risk assessment tool, taking into account also other types of vulnerable objects.

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References22Analysis of the potential effects of dam break flooding using a GIS-tool for risk assessment in mountain regions

References

BUWAL 1999: Risikoanalyse bei gravitativen Naturgefahren - Methode, Fallbeispiele und Daten (Riskanalyses for gravitational natural hazards). Bundesamt für Umwelt, Wald und Landschaft (BUWAL). Umwelt-Materialen Nr. 107, 1-244.

Cannata and Marzocchi 2011:‘Two-dimensional dam break flooding simulation: a GIS embedded approach. Natural Hazard, accepted for publicationNatural Hazards

Maggi R. et al, 2009: Evaluation of the optimal resilience for vulnerable infrastructure networks. An interdisciplinary pilot study on the transalpine transportation corridors, NRP 54 “Sustainable Developmentof the Built Environment”, Projekt Nr. 405 440, Final Scientific Report, Lugano.

Marzocchi and Cannata, 2009. Two-dimensional dam break flooding simulation: a GIS embedded approach.Proceedings of FOSS4GIS 2009

OFAT OFEE OFEFP (1997) R d ti 1997 P i t d d dOFAT, OFEE, OFEFP (1997), Recommendations 1997. Prise en compte des dangers dus aux mouvements de terrain dans le cadre des activités de l'aménagement du territoire, 42 pages.

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THANKS FOR THE ATTENTIONTHANKS FOR THE ATTENTION

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Documents

Analysis of the potential effects of dam break flooding ...€¦ · Mirko Baruffini, Maurizio Pozzoni and Roberto Marzocchi Institute of Earth Sciences, University of Applied Sciences