28. October 2015

FEWS-RISK: A STEP TOWARDS RISK-

BASED FLOOD FORECASTING

D. Bachmann

D. Eilander, A. de Leeuw, K. de Bruijn, F. Diermanse, A. Weerts, J.

Beckers, P. Gijsbers, M. Ponziani (Deltares, NL)

L. Boelee, C. Hazlewood, E. Brown (HR Wallingford, UK)

FEWS-User Days 2015, Deltares Delft

28. October 2015 Daniel Bachmann

28. October 2015

Common practice in operational flood forecast

Hydrology (catchment)

Hydrodynamic (river)

Meteorology (catchments)

Forecasted

process chain System river

t

h

Precipitation,

temperature,

wind etc.

Discharge

Water level

Water level

time series

Daniel Bachmann

28. October 2015

How to make a decision based on water levels?

Daniel Bachmann

• How will my flood defence line

perform?

• What will be the impacts of

flooding? Crisis

manager

System river

t

h

Water level

time series

28. October 2015

Extension by workflow 1

Hydrology (catchment)

Hydrodynamic (river)

Meteorology (catchments)

Forecasted

process chain

System river and flood

defence line

t

h

Water level

Failure

analysis (flood defence line)

In advance

Fragility

curve

Reliability

transformation

pf = 100%

Failure

probability

time series

Daniel Bachmann

28. October 2015

The concept of Fragility curves (FRC)

Summary of the performance or failure probability of a

structure depending to the load (e.g. water level [m])

Daniel Bachmann

28. October 2015

Determination of Fragility curves (FRC)

Daniel Bachmann

INPUT: Geometry, zonation, sub soil, soil

parameter etc.

28. October 2015

Support for decision makers by workflow 1

• Where is my weak section given the

hydraulic load?

• Where and when inspection should

increased or emergency measures

should be taken?

• Where and when a breach is

probable?

System river and flood

defence line

t

h

pf = 100%

Failure

probability

time series

Daniel Bachmann

Crisis

manager

28. October 2015

What happens if a breach occurs?

• How fast, how much and where the

water will flow?

• How relevant is the protection task

of this section?

• When and which emergency

measures should be triggered?

System river, flood

defense line, hinterland

Crisis

manager

Daniel Bachmann

28. October 2015

National Information system Floodmapping

Daniel Bachmann

Predicted hazard: Waterdepth after dike

failure for pre-calculated scenarios

28. October 2015

What happens if a breach occurs?

• How fast, how much and where the

water will flow?

• How relevant is the protection task

of this section?

• When and which emergency

measures should be triggered?

System river, flood

defense line, hinterland

Crisis

manager

Daniel Bachmann

28. October 2015

Extension by workflow 2

Breaching (flood defence line)

Impacts (protected area)

Police

Transformer

School

System river, flood

defence line, protected area

Hydrodynamic (river)

Hydrodynamic (protected area)

Forecasted

process chain

Water level

Discharge

Impacts to

people, critical

infrastructure

etc.

Flood spreading,

hydraulic values

Hospitall

Hydrology (catchment)

Daniel Bachmann

28. October 2015

Crisis

manager

Police

Transformer

School

System river, flood

defence line, protected area

Impacts to

people, critical

infrastructure

etc.

Flood spreading,

hydraulic values

Hospitall

Support for decision makers by workflow 2

Daniel Bachmann

• How fast, how much and where the

water will flow?

• How relevant is the protection task

of this section?

• When and which emergency

measures should be triggered?

28. October 2015 Daniel Bachmann

28. October 2015

The Rotterdam area and dike rings

• Western part of the Netherlands at the delta of Rhine

and Maas rivers to the North Sea

• Highly populated area (ca. 1.3 million people)

• High flood protection standards

Daniel Bachmann

Delft

28. October 2015

Reliability analysis

• 15 dike sections (14 in Ijsselmonde and 1 in Pernis)

• Pre-calculated fragility curves available

Daniel Bachmann

28. October 2015

Examples fragility curves

• Available fragility curves: km14_1, km47, Pernis

• Manipulated fragility curves: km14_1, km47 (demonstration

purpose); 50 % weaker as determined

Daniel Bachmann

28. October 2015

Hydrodynamic model: Discretization

• Tool: Subgrid software (part of 3di-package)

• 500 km² model domain with ca. 40 000 quad tree

elements (computational elements)

• Quad tree resolution: 100x100 m (min)/400x400 m (max)

• Subgrid resolution: 25x25 m (Lidar-data)

Daniel Bachmann

28. October 2015

Hydrodynamic model: Boundary condition

• 3 Dirichelet-boundary (water level time series 50 h model-time)

• Assumptions (demonstration purpose): • Based on flood event November 2007 (could be also forecasted

data);

• Maeslant-Barrier is not closing

• 25% increase of water levels

Daniel Bachmann

28. October 2015

Impact analysis

• Qualitative impact analysis

• Focus on persons (CBS-data) and critical infrastructure

(OSM-data)

Daniel Bachmann

28. October 2015 Daniel Bachmann

28. October 2015

Customization workflow 1

Daniel Bachmann

28. October 2015

Hydrodynamic analysis without breaching

Daniel Bachmann

Computational time: ca. 45 min (Intel Core i5-

3230M CPU 2.60 GHz)

28. October 2015

Reliability transformation

Daniel Bachmann

Failure

probability

time series

with

thresholds

Water level

time series at

dike sections

28. October 2015

Spatial distribution of dike performance

Daniel Bachmann

28. October 2015

Support for decision makers by workflow 1

• Where is my weak section given the

hydraulic load?

• Where and when inspection should

increased or emergency measures

should be taken?

• Where and when a breach is

probable?

Daniel Bachmann

28. October 2015 Daniel Bachmann

28. October 2015

Customization workflow 2

Daniel Bachmann

28. October 2015

Breach development

Daniel Bachmann

Starting

breach

development

by defined

failure

probability

(here 50 %)

Water level

time series at

dike sections

28. October 2015

Flood spreading breach km14_1 and km47

Daniel Bachmann

28. October 2015

Qualitative Impact analysis: What happens when?

Daniel Bachmann

28. October 2015

Qualitative Impact analysis and evacuation

Daniel Bachmann

28. October 2015

• How fast, how much and where the

water will flow?

• How relevant is the protection task

of this section?

• When and which emergency

measures should be triggered?

Crisis

manager

Support for decision makers by workflow 2

Daniel Bachmann

• Extend current operational flood forecast systems with

approaches of strategic flood risk analysis • Probability of failure

• Impact analysis

• Provide transformed and compact model-base

forecasted information to support decision makers • Weak spots in the flood defense line (Workflow 1)

• Impacts of flooding (Workflow 2)

• Supports the development and adaptation of emergency

measures in real-time

28. October 2015

Summary

Daniel Bachmann

28. October 2015

Outlook: Ongoing projects

Daniel Bachmann

• Deltares ID-Lab project: Coupling of global forecasting

models as boundary conditions to local models

• Deltares ID-Lab project: Combining real-time sensor

data from a dike (DAM-Live) with fragility curves

• TO2 project Crisis management (program Safe

Society): Integration of ensemble forecast and

quantitative impact analysis

28. October 2015

Outlook: Coupling to global models

Daniel Bachmann

Impacts

Police

Transformer

School

Global forecasts

Hydrodynamic (river/coastal &overland)

Forecasted

process chain

local water levels

Inundated area

Impacts to

people, critical

infrastructure

etc.

Flood spreading,

hydraulic values

Hospitall

Global Forecast

storm surge /

discharge

Local impact forecast

28. October 2015

Outlook: Combining with sensor data

Daniel Bachmann

Real time dike data,

e.g. seepage line

Precalculated

fragility curve

28. October 2015

Outlook: Including ensemble forecast

Daniel Bachmann

Precalculated

fragility curve

Ensemble forecast for

water level- time series

Ensemble forecast for failure

probability- time series

Ensemble forecast

for breach width-

time series

28. October 2015

Outlook: Including quantitative impact analysis

Daniel Bachmann

Ensemble forecast for flooding

28. October 2015 Daniel Bachmann

More information at the next FEWS-user

days 2016!

28. October 2015

FEWS-RISK: A STEP TOWARDS RISK-

BASED FLOOD FORECASTING

D. Bachmann

D. Eilander, A. de Leeuw, K. de Bruijn, F. Diermanse, A. Weerts, J.

Beckers, P. Gijsbers (Deltares, NL)

L. Boelee, C. Hazlewood, E. Brown (HR Wallingford, UK)

FEWS-User Days 2015, Deltares Delft