natural hazards and risk analysis in mountain regions

Natural Hazards and Risk Analysis in Mountain Regions,

‘Blockkurs’ GEO 805

Field part, Lauterbrunnen, 4-6 September, 2019

Christian Huggel, UZH

Brian McArdell, WSL

Demian Schneider, Tiefbauamt, Kanton Bern

Randy Muñoz, UZH

Hazard and Risk Analysis Course, Lauterbrunnen

Keystone / VBS / sda / Blick

Cengalo/Bondo events 2017


Lin Nyunt / The Telegraph


20Minuten

July 2019

Debris flow from subglacial drainage, Triftbach, Zermatt


Learn, collect experiences


Informed and critical thinking and assessment


Recognize problems and uncertainties


Orders of magnitude, no fine tuning


Estimate, generalize, leave out


Working under pressure


Time management


Improvisation


FUN !


• There is not THE solution

• Collect experiences, feedback is important

• We support you but you decide


Learning objectives:

After this course you should be able to:

… understand and correctly apply the terminologies related to hazards,

vulnerability, damage potential and risk.

… perform a hazard assessment and hazard mapping of debris flows and

floods in mountain areas.

… distinguish a variety of vulnerability-categories and perform the

according data acquisition and mapping.

… realize a simple risk assessment and -mapping on the basis of the

hazard- and vulnerability/damage potential-mapping.

… analyze hazards, vulnerability/damage potential and risk for a given

case study appropriately and derive according recommendations for

stakeholders.


Study area and processes: limitations


Concentration on debris flows (torrents) and floods

Rock fall, landslides, avalanches are not considered


Study area Lauterbrunnen

Rybibach

Mättlibach

Gryfenbach

Fluebächli

Louwibach

Weisse Lütschine


2009


2012


2013


Louibach


Spiessbach


Flood process


2005 floods in Switzerland

Bern Entlebuch

Processes


Processes

Damming and lateral overflow

Klosters - 2005 Schattdorf - 2005

Emmental – Kemmeribodenbad - 2014

N. Wächter


Processes

Lateral overflow

N. Wächter

Engelberger Aa 2005

Planat.ch


Processes

Blocking at structural

barriers such as bridges.

Damming and lateral

overflow

Thun

Emmental 2014

20 minuten


Lateral undercuttingEngelberg

Sediment transport and deposition

Processes


Undercutting

Río Vilcanota, Aguascalientes (Machu Picchu, Peru), Jan. 2010

Processes


Transformation into

torrent and debris flow processes

Lütschinental

Processes


Unchannelized (hillslope) debris flows

Processes


Catchment

• Precipitation intensity and

duration

• Characteristics of soil and

surface (glacier, bedrock,

vegetation etc)

• Catchment size

• Topography

• etc

Lauterbrunnen

Runoff coefficient

Processes: runoff generation


Processes: Precipitation

Meteoswiss precipitation radar


Processes: Precipitation

Precipitation radar in the Andes of Peru

U Stuttgart / UZH / UNASAM


Runoff response depending on rainfall and catchment characteristics

Runoff response

slideshare.net


Extreme value analysis on the basis of

observed runoff measurements

BWG, 2003


Typical return periods

(‚Jährlichkeiten‘)

• 30 yr return period flood (30-jährliches HW)



• Extreme flood (EHQ)


Flood estimates in catchments without runoff measurements

• different, mainly empirical methods

• partly distinction of medium-sized (10-500 km2) and small catchments (<10km2)

e.g. Kölla (1986):


bFnaHQ 100bFnaQ max

HQ100 100-jährliche Abflussspitze [m3/s]

Qmax maximale Abflussspitze [m3/s]

a regionenspezifischer Parameter [-] Region A1: 4,36 für HQ100 bzw. 6.03 für Qmax

b regionenspezifischer Parameter [-] Region A1: 0.64 für HQ100 und Qmax

Fn Einzugsgebietsgrösse [km2] Karte

GIUB’96


Hazard mapping


Prozess Low intensity Medium

intensity

High intensity

Rockfall E < 30kJ 30 < E <

300kJ

E < 300kJ

Landslide v: ≤ 2cm/Jahr v: dm/Jahr (>

2cm/Jahr)

starke

Differentialbeweg

ungen;

v > 0.1m/Tag bei

oberflächlichen

Rutschungen;

Verschiebungen >

1m pro Ereignis

Debris flow h < 1m h > 1m

Intensity - debris flow Intensity - Flood

E = kinetic energyh = Thickness of debris flow depositsv = long-term average slope deformationafter Lateltin, 1997.


Probability Return period


123

456

789

0

red

blue

yellow

whiteor hatched

yellow-whiteIn

te

ns

ity high

medium

low

high medium low

Probability

residualrisk

nach Raetzo et al., 2002

Gefahrenstufe Sachliche Bedeutung Raumplanerische

Bedeutung

Rot Erhebliche Gefährdung Verbotsbereich

Blau Mittlere Gefährdung Gebotsbereich

Gelb Geringe Gefährdung Hinweisbereich

Gelb-weiss Restgefährdung Hinweisbereich

Weiss Keine Gefährdung* Keine Einschränkungen*

*nach derzeitigem Wissensstand

Nach BWG, 2001


Hazard maps are instruments of spatial planning to delimit endangered areas

and to prevent from damages.

Hazard maps often do not exactly correspond to actually occurring processes

and need to be updated.

Example

Brienz 2005


Hazard zone limits cannot be understood as precise delimitation of processes

Example

Bondo 2017(Keystone)


Hazard mapping in the broader land-use planning and construction processes

Guidelines Kanton

Graubünden, 2017


The final presentation

should take 10 minutes (plus ca. 5 min discussion) and all the

treated aspects need to be involved, such as:

1. Debris flow hazards (values / map) (you can focus on 2

catchments out of 4)

2. Flood hazards (values / map)

3. Damage potential (classes / map)

4. Risk (matrix / values / map / hotspots)

5. Possible measures with a limited budget (priority list)

6. Discussion / further information


Status of examination of the course:

Passed / not passed

natural hazards and risk analysis in mountain regions

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