1. Hydrologycal modeling of
boundary conditions of flash
floods
Peter Hegedüs
University of Pécs, Hungary
YWP 2012 May 16-18, Sofia

2. Introduction
• What is a flash floods?
• What are the earlier cases?
• Why are we dealing with kind of floods?
• How can we measure boundary
conditions?
• What are the main goals of our study?

3. Generation of flash floods
• Increasing weather extremities
• Intensity of rainfall events are growing
• Rapid runoff according to relief
• Short concentration time

4. Earlier examples
• Boscastle (UK) 2004
• Rapid City (South-Dakota, USA)
1972
• Mátrakeresztes (Hungary, 2005)
Economic & Infrastructural damages
Private property losses
Life losses

5. Major property damages
• ~140m3/s peak discharge
• 100 houses damaged
Boscastle (UK)

6. Rapid city: dam breach

7. Pilot area properties
Bükkösd Stream’s watershed in SW
Hungary
• Small low-mountainous & hilly region
• Quite high relief
• 7 major flood events from the earlier
decades
• Relatively representative area (1.7 km 2 )

10. Measurement instruments
• Rain gauges
with EM-50 loggers
(Decagon Devices Inc.)
• 5-TM TDR-type
soil moisture sensors
• Stream gauges
http://ttk.pte.hu/kornyezettudomany/baross/galeria_kepek/decagon.JPG

11. Gauges indicated on orthophotos

12. Data analysis
• HEC-HMS 3.4 hydrologic modeling
program (Davis, USA)
• Arc GIS 9.2
• AGROTOPO soil database
• CLC land cover

13. Results
• Precipitation is crucial, however soil
properties are very important
• Time of concentration is also considerable
• Flood occurance in late spring, summer

14. Soil moisture
• Monthly averages (May, June) usually
between 12.1 – 19.8 % (VWC)
• Major differences

15. Time of concentration
• Peak discharge & precipitation values needed
• Intensity can be variable between a short range
of area
• More rapid concentration on tributary streams

16. Simulation of the flood event in
2010 May
• Numerous data
needed: water
content, canopy
cover, stream
discharge etc.
• Western and
eastern
watershed
differences

17. Conclusions
• HEC-HMS is suitable for modeling
• Plethora of data – consideration of
boundary condition analysis is necessary
• Rainfall intensity greatly varies –
secondary effect problems
• VWC & soil saturation calculation must be
cautious – software sensibility

18. Acknowledgement
The present study was funded by the “TÁMOP
4.2.1.B-10/2/KONV-2010-0002” Scolarship
(Developing competitiveness of universities in
the South Transdanubian Region)

19. Thank you for your attention!