IJEGE.2006-01.S-05IJEGE.2006-01.S-05

L. ERMINI, N. CASAGLI & P. L. ERMINI, N. CASAGLI & P. FARINAFARINA

Presenter：高志文自然災害防治研究室

Landslide dams may form suddenly and unexpectedly, there by posing hazards that must be rapidly assessed.

The application of satellite(satellite( 衛星衛星 )) and ground based ground based radarradar systems(systems( 地面雷達系統地面雷達系統 )), can really represent a successful tool for the management of emergencies deriving from damming events.

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Most important issues connected to a landslide that threat to block a river valley are:

Is the landslide capable of blocking the river provoking a dam formationformation?

Which will be the post formation behaviorformation behavior of the landslide dam?

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Length of time before failure of failed landslide dams, based on206 case histories (after CASAGLI & ERMINI, 2003)

90%

38%

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Formation ： 1404 Time ： 1419~1774 (six times) Location ： Passirio River basin (Alto Adige, Italy) Reason ： the landslide toe reactivation Injury ： provoked much damages to the downstream reach of the valley where the village of Merano

Formation ： September 30th 1513 Time ： May 20th 1515 (after 20 months) Location ： Biasca (Switzerland) Injury ： more than 600 people died in the consequent downstream flood

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Time ： March 21st 1812 Location ： Quarto sul Savio (Forli, Italy) Reason ： upstream flooding Injury ： on this occasion 18 people died, most of them drowned in the lake

Time ： February 14th 1855 Location ： Pieve Santo Stefano Reason ： rapid rock-slide Injury ： seven deaths and the destruction of several artworks

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Time ： April 14th 1899 Location ： near Marradi (Firenze) Reason ： very rapid rock-slide Injury ： the complete submersion of the Gamberara village causing 3 victims

Time ： February 1st 1996 Location ： Marano near Gaggio Montano (Bologna) Reason ： permitted a successful excavation of the landslide toe, avoiding a complete blockage

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CANUTI et alii (1998)

CASAGLI & ERMINI (1999)

Blockage Index ： (阻塞指數 )

ERMINI & CASAGLI (2003)

dimensionless blockage index ： ( 無因次阻塞指數 )

AVLogI d

b

d

db HA

VLogI

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Ratio between dam volume and dam height (after ERMINI &CASAGLI, 2003) 10

CASAGLI & ERMINI (1999) followed the original approach of SWANSON et alii, (1998) and proposed some analyses, updated by the work of ERMINI (2003)

Dimensionless Constriction Index(無維收縮指數 )

vp

lll

WQDDWvDCI 30

moving landslide is not able to block the river channel in all those situation where the DCI < 0.002 (ERMINI, 2003).

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Synthetic Aperture Radar (SAR) 合成孔徑雷達Differential SAR Interferometry (DInSAR) 差分干涉處理ground-based systems(GBInSAR) 地面系統Permanent Scatterers (PS) 永久散射體

the remote assessment of ground movements related to landslides,can be measured to very modest displacements 12

The world's smallest Synthetic Aperture Radar

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CORTENOVA ROCKSLIDE (LECCO, ITALY)CORTENOVA ROCKSLIDE (LECCO, ITALY)

Time ： December 1st 2002

Location ： Lombardia Prealps (northern Italy)

Reason ： after two weeks of prolonged and intense rainfall, with values up to 128.4 mm/day

Injury ： wiping out 15 houses and 3 factories

Solution ： the potential landslide evolution required the evacuation of about 900 people living close to the run-out area .

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Rainfall registered in the landslide area during November 200216

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Carbonile slidingCarbonile sliding

Time ： 1984 to 1985

Location ： Pelago municipality (Firenze, Italy)

Reason ： coupled with the weakness of the involved materials,the most important cause for the sliding movement

Injury ： induce the evacuation of 8 houses and severe damages to industrial manufacture buildings

Solution ： it was realized a system for draining water from the landslide area, consisting in the installation of surface and underground drains 19

Carbonile (Firenze, Italy) 20

Grain size analyses and geotechnical tests on debris materials forming landslide dams should be more extensively carried out, in order to understand their physical behaviour and forecast both the evolution of processes.

Geomorphological Indexes for forecasting the evolution of damming events can be of help in the emergency management, giving “easy to be applied general criteria.”

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On wide sectors of a valley, very detailed measures of surface deformation associated to landslides that threat to dam rivers, with particular reference to not accessible sites.

Ground based systems can be more properly installed for the emergency management, allowing the local monitoring of slopes and of their toe interactions with river channels.

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Thanks for listeningThanks for listening

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