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Flood Event 2021 in Germany: More Research Into Practice!

Abstract

First part: Some information about the tragic flood event 2021 in Germany (from an observer perspective) Second part: some idea how we can do it better (from a research point of view)
Flood Event 2021 in Germany:
More Research Into Practice!
Bachmann, D.
HOWAMAN Joint Webinar on "Flood Risk Management in Iran and Germany"
Research group Flood Risk Management
University of applied sciences Magdeburg-Stendal
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Prof. Dr.-Ing. Daniel Bachmann Flood Event 2021 in Germany: More Research Into Practice Digital, 8.9.2021
Part I: Flood event 2021
- From an observer perspective
Magdeburg
Western part of
Germany
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Prof. Dr.-Ing. Daniel Bachmann Flood Event 2021 in Germany: More Research Into Practice Digital, 8.9.2021
1. Flood event 2021
Causes
Weather forecast 12th of July
Low-pressure area Bernd
brings intense, long lasting
rainfall
The whole coming week
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Prof. Dr.-Ing. Daniel Bachmann Flood Event 2021 in Germany: More Research Into Practice Digital, 8.9.2021
1. Flood event 2021
Causes
Topography
small and medium size rivers with origin in
medium range mountains like the Eifel
Steep slope and narrow valleys
Getting less step and wider in direction of
Rhine and Maas-river (large size rivers)
Ahr
Vicht
Rur
Wupper
Erft
Maas
Rur
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Prof. Dr.-Ing. Daniel Bachmann Flood Event 2021 in Germany: More Research Into Practice Digital, 8.9.2021
1. Flood event 2021
Consequences (small / medium size river)
Hydrology + Hydrodynamic
Intense, long lasting rainfall
(about 150 mm / 24 h)
Steep slopes, narrow
valleys
+=>
Steep => fast flood wave
Narrow => high water levels,
“small” floodplains
Steep => high velocities
Flood type
Fast, but predictable
fluvial (river) flooding
(flash flood) mixed with
pluvial flooding
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Prof. Dr.-Ing. Daniel Bachmann Flood Event 2021 in Germany: More Research Into Practice Digital, 8.9.2021
1. Flood event 2021
Consequences (small / medium size river)
Economy, people, critical
Infrastructures, ecology
source: BBK, 2021
source: Spiegel, 2021
Casualties (230) due to flooding
=>
Failure of water supply and electricity
(critical infrastructure)
source: dpa, 2021
Economy and
people
(psychosocial)
source: wdr, 2021
Ecology
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Prof. Dr.-Ing. Daniel Bachmann Flood Event 2021 in Germany: More Research Into Practice Digital, 8.9.2021
1. Flood event 2021
Retrospective modelling based on open source data
Hydrodynamic and damage model
Vicht (small)
Rur (medium)
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Prof. Dr.-Ing. Daniel Bachmann Flood Event 2021 in Germany: More Research Into Practice Digital, 8.9.2021
1. Flood event 2021
Retrospective modelling based on open source data
Hydrodynamic model
1d-2d coupled model
Open source data
Open tools: PROMAIDES and QGIS
https://promaides.h2.de
Fast set-up
Vicht (small)
18 km river
70 km² 10 x 10 m
floodplain
2d rainfall in 12 h
BC: reservoir /
rainfall to catchment
Rur (medium)
88 km river
275 km² 10 x 10 m
floodplain
4d in 10 h
BC: reservoir
/tributaries
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Prof. Dr.-Ing. Daniel Bachmann Flood Event 2021 in Germany: More Research Into Practice Digital, 8.9.2021
1. Flood event 2021
Retrospective modelling based on open source data
Hydrodynamic model: results Vicht (small)
Rathausstraße
source: Stadt Stolberg, 2021
About 130! m³/s (normal discharge 1 m³/s)
About 1000 yearly event
https://www.youtube.com/watch?v=i1ULtuOOzcE
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Prof. Dr.-Ing. Daniel Bachmann Flood Event 2021 in Germany: More Research Into Practice Digital, 8.9.2021
1. Flood event 2021
Retrospective modelling based on open source data
Hydrodynamic model: results Rur (medium) (https://www.youtube.com/watch?v=xvhjf1XDFHE)
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Prof. Dr.-Ing. Daniel Bachmann Flood Event 2021 in Germany: More Research Into Practice Digital, 8.9.2021
1. Flood event 2021
Retrospective modelling based on open source data
Hydrodynamic model validation Rur (open source)
News paper
Social media
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Prof. Dr.-Ing. Daniel Bachmann Flood Event 2021 in Germany: More Research Into Practice Digital, 8.9.2021
1. Flood event 2021
Retrospective modelling based on open source data
Hydrodynamic model validation Rur (open source)
Satellite images
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Prof. Dr.-Ing. Daniel Bachmann Flood Event 2021 in Germany: More Research Into Practice Digital, 8.9.2021
1. Flood event 2021
Retrospective modelling based on open source data
Damage model
Categories: Direct Economic (housing, industry,
farming), affected and endangered persons
Open source data
Open tools: PROMAIDES and QGIS
https://promaides.h2.de
Fast set-up
Vicht (small)
10 x 10 m
Rur (medium)
10 x 10 m
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Prof. Dr.-Ing. Daniel Bachmann Flood Event 2021 in Germany: More Research Into Practice Digital, 8.9.2021
1. Flood event 2021
Retrospective modelling based on open source data
Damage model: results
Rough estimates because of data quality!
What it shows:
small river high damages
medium river medium damages
large river low damages
Vicht (small)
Economy: 30 50 Mio €
Affected: 4500 P
Endangered: 13 P
Rur (medium)
Economy: 25 – 35 Mio €
Affected: 2000 P
Endangered: 2 P
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Prof. Dr.-Ing. Daniel Bachmann Flood Event 2021 in Germany: More Research Into Practice Digital, 8.9.2021
Part II: More research into practice
source: BBK, 2021
source: Spiegel, 2021
Casualties (230) due to flooding
Failure of water supply and electricity
(critical infrastructure)
source: dpa, 2021
Economy and
people
(psychosocial)
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Prof. Dr.-Ing. Daniel Bachmann Flood Event 2021 in Germany: More Research Into Practice Digital, 8.9.2021
Strategic, long term
flood risk management
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Prof. Dr.-Ing. Daniel Bachmann Flood Event 2021 in Germany: More Research Into Practice Digital, 8.9.2021
2. Strategic (long-term) planning
Question
1. What is the most effective, sustainable flood risk mitigation measure?
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Prof. Dr.-Ing. Daniel Bachmann Flood Event 2021 in Germany: More Research Into Practice Digital, 8.9.2021
2. Strategic (long-term) planning
State of the art
Adapted reservoir
management
Reduction of peak
discharge xx m³/s
River widening
Reduction of water
level by xy cm
Dike slope
Reduction of
safety factor xy -
Catalogue with different type of flood risk
mitigation measures per catchment
(defined by EU flood risk management
directive)
But in general just a qualitative or a type
specific evaluation
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Prof. Dr.-Ing. Daniel Bachmann Flood Event 2021 in Germany: More Research Into Practice Digital, 8.9.2021
2. Strategic (long-term) planning
Solution
Holistic, catchment-based flood risk analysis
Measure are directly and transparently
evaluated and they are directly and
transparently comparable
(What is the most effective risk reduction measure?)
What is the value of my measure? (acceptance /
image)?
(Flood risk mitigation saves yearly money and lives
(statistically)!
Climate change and socio-economic change
are evaluated in an analogue way!
(Sustainable measure design!)
Climate change
Increase of flood risk
by xx €/a
Socio- economic
change
e.g. new housing area
Increase of flood
risk by xx €/a
Adapted reservoir
management
Reduction of flood
risk by xx €/a
River widening
Reduction of flood
risk by xx €/a
Dike slope
Reduction of
flood risk by xx
€/a
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Prof. Dr.-Ing. Daniel Bachmann Flood Event 2021 in Germany: More Research Into Practice Digital, 8.9.2021
2. Strategic (long-term) planning
Example
Risk-based planning of measures (project 2009)
Alternative
Decision criteria
Flood dependent (risk reduction)
Flood independent
Economic direct
[€/a]
Ecologic
[€/a]
Affected
persons
[Person/a]
Endangered
persons
[Person/a]
Cost
[€]
157.307 1.327 7 0,008 1
2115.991 74 21 0,011 447.052
33.497 8 3 0,001 40.407
455.692 0 0 0,000 100.000
more info
Transparent ranking
Decision matrix
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Prof. Dr.-Ing. Daniel Bachmann Flood Event 2021 in Germany: More Research Into Practice Digital, 8.9.2021
2. Strategic (long-term) planning
Question
1. What is the most effective, sustainable flood risk mitigation
measure?
2. Are we well-prepared for very unlikely events or dike
failure?
source: swr aktuel, 2021l
source: ard Tagesschau, 2021
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Prof. Dr.-Ing. Daniel Bachmann Flood Event 2021 in Germany: More Research Into Practice Digital, 8.9.2021
Flood hazard maps
Defined by EU flood risk management directive
Important for communication
Public available in the internet
3 hydrological scenarios
(10 a, 100 a, extreme (200 a))
Dike failure: no
2. Strategic (long-term) planning
State of the art
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Prof. Dr.-Ing. Daniel Bachmann Flood Event 2021 in Germany: More Research Into Practice Digital, 8.9.2021
Take more hazards into account
e.g. analyse also the HQ10 000! (10 000 yearly)
(hydrologic events)
e.g. analyse also failure events in the flood
defence line! (Failure of dike)
2. Strategic (long-term) planning
Solution
Hydrologic
events
Failure of dike
Compound
events
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Prof. Dr.-Ing. Daniel Bachmann Flood Event 2021 in Germany: More Research Into Practice Digital, 8.9.2021
2. Strategic (long-term) planning
Example
Flood scenarios for Teheran (Iran, project 2020)
1 of 28 scenarios: HQ10.000 (184 mm / 24 h)*Comparison flood 2021 ca. 150 mm / 24 h
source: swr aktuell
more infos
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Prof. Dr.-Ing. Daniel Bachmann Flood Event 2021 in Germany: More Research Into Practice Digital, 8.9.2021
2. Strategic (long-term) planning
Question
1. What is the most effective, sustainable flood risk mitigation
measure?
2. Are we well-prepared for very unlikely events or dike failure?
3. How are persons and critical infrastructure protected?
source: BBK, 2021
source: Spiegel, 2021
Deaths (230) due to flooding
Failure of water supply and electricity
(critical infrastructure)
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Prof. Dr.-Ing. Daniel Bachmann Flood Event 2021 in Germany: More Research Into Practice Digital, 8.9.2021
Flood “Risk” maps
Defined by EU flood risk management
directive
Important for communication
Public available in the internet
Interception land use with flooded area
Estimation number affected people
2. Strategic (long-term) planning
State of the art
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Prof. Dr.-Ing. Daniel Bachmann Flood Event 2021 in Germany: More Research Into Practice Digital, 8.9.2021
Take more types of flood consequences into
account
Affected and endangered persons
Critical infrastructures (CI) and cascading
effects
2. Strategic (long-term) planning
Solution
source: Allsop, 2004
Transformer
X household without
Electricity water
Water supply
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Prof. Dr.-Ing. Daniel Bachmann Flood Event 2021 in Germany: More Research Into Practice Digital, 8.9.2021
2. Strategic (long-term) planning
Example
Failure of critical infrastructure in Accra (Ghana, project 2020)
more infos
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Prof. Dr.-Ing. Daniel Bachmann Flood Event 2021 in Germany: More Research Into Practice Digital, 8.9.2021
Operational / short-term flood forecasting
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Prof. Dr.-Ing. Daniel Bachmann Flood Event 2021 in Germany: More Research Into Practice Digital, 8.9.2021
3. Flood forecasting (short-term)
Question
1. Which information are required short before / during a
flood event?
source: FAZ, 2021
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Prof. Dr.-Ing. Daniel Bachmann Flood Event 2021 in Germany: More Research Into Practice Digital, 8.9.2021
3. Flood forecasting (short-term)
State of the art
Standard prediction chain with forecast of
discharge / water levels 24 / 48 h in advance
Warning are given as
„Discharge at gauge xy will be zm³/s“
„Water level at gauge xy will be zm“ etc. Hydrology
(catchment)
Hydrodynamic
(river)
Meteorology
(catchment)
t
h
Precipitation,
Wind
Temperature
Discharge
Water level
Prediction
times series
water level
System river Prediction chain
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Prof. Dr.-Ing. Daniel Bachmann Flood Event 2021 in Germany: More Research Into Practice Digital, 8.9.2021
3. Flood forecasting (short-term)
Solution
When, how much, how fast and
where water will flow? (flood
spreading)
When and where are persons
and critical infrastructures
highly endangered?
Where I have to close roads?
Evacuation, where to start, until
when?
Am I / my house / my assets
endangered? When?
Prediction of information far beyond water
levels at gauge stations
First responders
People
Crisis management
source: THW source: Bez. Reg.
Duesseldorf
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Prof. Dr.-Ing. Daniel Bachmann Flood Event 2021 in Germany: More Research Into Practice Digital, 8.9.2021
3. Flood forecasting (short-term)
Solution
Consequences
(Hinterland)
Police
Transformer
School
System river
Hydrodynamic
(river / hinterland)
Prediction chain
discharge
Damage to
persons, CI
etc.
Flood spreading
Hospitall
Hydrology
(catchment)
Water level /
flow velocity
Extend the standard prediction chain in flood
forecasting
Prediction of flood spreading and damages to
persons, CIs and economy 24 to 48 h in
advance
Warning are much easier to interpret:
„in 5 h street xy needs to be closed“
„in 4 h hospital xy has to be evacuated“
„in 5 h transformer xy will be flooded; electricity
in area 1,5,6 will be shut off “
etc.
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Prof. Dr.-Ing. Daniel Bachmann Flood Event 2021 in Germany: More Research Into Practice Digital, 8.9.2021
3. Flood forecasting (short-term)
Example
Prototyp impact based forecasting for Dumfries (Scotland, project 2016)
more infos
Probability water level > 0,5 m in 5 h;
Is it still possible to evacuated?
%
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Prof. Dr.-Ing. Daniel Bachmann Flood Event 2021 in Germany: More Research Into Practice Digital, 8.9.2021
4. Conclusion
Part I: Flooding in July 2021
Intense, long lasting rain fall in steep narrow valleys
Fast river floods (around 1000 a event)
With high consequences at small/medium river areas
High number of casualties and CI-failure
Part II: research into practice
Approaches would not prevent the flooding:
risk-based strategic planning / risk-based forecasting
Preparation would be better
Number of casualties and CI-failure would be less
Flood Event 2021 in Germany:
More Research Into Practice!
Bachmann, D.
HOWAMAN Joint Webinar on "Flood Risk Management in Iran and Germany"
Research group Flood Risk Management
University of applied sciences Magdeburg-Stendal
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