Hydrologycal modeling of boundary conditions of flash
floods
Peter HegedüsUniversity of Pécs, Hungary
YWP 2012 May 16-18, Sofia
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?
Generation of flash floods
• Increasing weather extremities
• Intensity of rainfall events are growing
• Rapid runoff according to relief
• Short concentration time
Earlier examples
• Boscastle (UK) 2004
• Rapid City (South-Dakota, USA)1972
• Mátrakeresztes (Hungary, 2005) Economic & Infrastructural damages
Private property losses
Life losses
Boscastle (UK)
Major property damages
• ~140m3/s peak discharge• 100 houses damaged
Rapid city: dam breach
Pilot area propertiesBükkösd 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 km2 )
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
Gauges indicated on orthophotos
Data analysis
• HEC-HMS 3.4 hydrologic modeling program (Davis, USA)
• Arc GIS 9.2
• AGROTOPO soil database
• CLC land cover
Results
• Precipitation is crucial, however soil properties are very important
• Time of concentration is also considerable
• Flood occurance in late spring, summer
Soil moisture
• Monthly averages (May, June) usually between 12.1 – 19.8 % (VWC)
• Major differences
Time of concentration
• Peak discharge & precipitation values needed• Intensity can be variable between a short range
of area• More rapid concentration on tributary streams
Simulation of the flood event in 2010 May
• Numerous data needed: water content, canopy cover, stream discharge etc.
• Western and eastern watershed differences
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
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)
Thank you for your attention!