1. Flood Mapping Workshop
Dublin, 17th to 19th September 2008
Where and how
to do Preliminary flood risk assessment? Flood mapping must help to answer: the Czech Republic situation.
Jan Daňhelka
Czech Hydrometeorological Institute
Na Sabatce 17, Praha-Komorany, CZ
Michaela Brejchova, Karel Drbal, Josef Reidinger

2. What has been done already in the CZ Historical floods
OUTLINE
What has been done already in the CZ
Historical floods
What is a significant risk?
What is extreme flood?
Some other issues of risk evaluation
Reporting

3. Introduction
Floods - the most important natural risk in the CZ
heavy precipitation
snow melting
flash floods CZ
area of km2
km of streams
9 252 km of remarkable streams
Water Act of the Czech Republic 254/2001Sb

4. Introduction
FRD demands?
PFRA outputs = maps and other information

5. Existing data and information
Inundation areas Q5
Q20
Q100
active inundation
River basin management plan of the Czech Republic
(May 2007)
preventive measures to reduce damage by flooding
Chapter D of River Basin District Plans

6. Existing data and information
Flood hazard and flood risk assessment methodology (Drbal et al., 2005)
Project on further improvement of methods of flood risk and flood damages estimation including implementation of FRD.
Information System Flood Resident (ISFR)
number of residents aggrieved by Q100, Q20
PFRA - flood with high probability = Q20
- flood with medium probability = Q100
- flood with low probability = ?

7. Historical Floods
Pre-instrumental period (before 1800)
chronicles
dates (August 1118, June 1432 etc.)
magnitude? (since the time of Noah)
inundation? (churches and streets that were flooded)
flood marks (very few)

8. Historical Floods
Instrumental period (1800 – 1980)
historical measurements
pictures, photographs
flood marks
reports

9. Historical Floods

10. Historical Floods
Is inundation the same?
- Mapping of flood protection and terrain changes.

11. What is a significant risk?
No pan European criteria
How to set some threshold?
Potential damage (direct)
Affected residents – first approximation
other types of risks

12. What is a significant risk?
Czech Republic
Q100
90 381 buildings ( used for living)
households
people (3,5 %)
1 499 municipalities
50 municipalities > inhabitants
395 municipalities > 100 inhabitants.
Olomouc
Brno  199
Prague  935
Uherske Hradiste - 14 578

13. What is a significant risk?

14. What is a significant risk?

15. What is a significant risk?

16. What is a significant risk?

17. What is an extreme flood?
FRD 2nd phase
Q500 ?
Probable maximum flood ?
Historical flood extent ?
Flood plain delimitation based on terrain or soil mapping ?
Hydraulic modeling
steady x unsteady flow
design hydrograph
confluences
Verification over historical floods…

18. Other applications based on flood risk?
Reinsurance brokers
Flood damage models
Flood extent
flood depth in selected profiles (above the bankfull)
interpolation along the stream
precision? - important are large cities (damages) only!
Intersect with insurance portfolio
Apply damage functions (curves)
Base for decision of billions of Euro business!

19. Reporting
PFRA outputs
Make available to GP
Make available to the Commission
CZ view
Use existing databases and information systems in the CZ
Reporting the work, not the full outputs

20. Common water management information portal
Reporting
Common water management information portal

21. Flood information system POVIS
Reporting
Flood information system POVIS

22. Conclusion
So, how flood mapping should support PFRA?
use existing maps (Q100, Q20)
help to define „significant risk“ threshold
mapping (localization) of flood protection measures
GIS procedures of flood plain delimitation?
verification of historical flood inundation data
Preparing the outputs of PFRA which in a fact are flood maps

23. THANK YOU FOR YOUR ATTENTION
Flood Mapping Workshop
Dublin, 17th to 19th September 2008
THANK YOU FOR YOUR ATTENTION
Jan Daňhelka
Research activities of CHMI in the field of CC impact on hydrology
Czech Hydrometeorological Institute
Na Šabatce 17, Praha-Komořany, CZ