2. presentation hp

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!