1 / 23

Flash flood forecasting in Slovakia

Flash flood forecasting in Slovakia. Michal Hazlinger Slovak Hydrometeorological Institute Ljubljana 16.5.2012. Input informations - precipitation. Problems with measurement – discrete raingauge stations Problems with data gaps Automatic station network since 2004

fern
Download Presentation

Flash flood forecasting in Slovakia

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Flash flood forecasting in Slovakia Michal Hazlinger Slovak Hydrometeorological Institute Ljubljana 16.5.2012

  2. Input informations - precipitation • Problems with measurement – discrete raingauge stations • Problems with data gaps • Automatic station network since 2004 • Necessarity of spatial precipitation field – based on combination of radar measurement and station data – INCA precipitation field

  3. Input data in Myjava watershed and „Orava“ pilot basins

  4. INCA precipitation field

  5. Forecast of runoff • Hydrologic models - problems with events with very short duration • Testing of HBV variation for Slovak condition – HRON • 1 hour forecasting step • Calibrated for extreme events in 2011 (Gidra basin) and 2010 (Oravica river basin) • Validation in 2010 resp. 2011

  6. Results of HRON simulation in Gidra river basin Rainfall input – APS and INCA precipitation field analyzes

  7. Dispersion of simulated and observed datas Calibration data set Validation data set

  8. Hydrologic model Rainfall – runoff model HEC-HMS Basin model based on CN method for calibration used input data from raingauge stations (1 minute and 1 hour time step), from watergauge stations and INCA precipitation field (based on shp files, 5 min. time step, 1 x 1 km spatial resolution) Calibration in Handlovka and Gidra river basin Calibrated for extreme events Output - Hydrogram of outflow or possibility / propability of exceeding warning level

  9. Hydrological models • Input from INCA precipitation field analyses (based on *.shp, 5 min. timestep, 1 x 1 spatial resolution) • HEC – HMS rainfall – runoff model – able to compute runoff in small watersheds • System based on estimation of flood potential by CN method – 3 states of saturation

  10. Calibration results for Handlovka and Gidra river basins Gidra 7.6. 2011 Handlovka 10.7. 2007 Handlovka 15.8. 2010

  11. Case Study – Gidra (Píla) 30 km2 200 – 600 m a.s.l. Average slope 10-15° granite + limestone region forested almost 100% 1000 –year flood 7.6.2011

  12. Calibration outputs

  13. Handlovka basin model

  14. Handlovka – calibration and validation outputs

  15. Other methods available for flash flood forecasting • 3 different tools • 1. calibration of hydrological models for various types of watershed (based on natural condition) – weak coverage of Slovakia • 2. estimation of flood potential - based on CN method • 3. estimation of flood potential – based on parameters of watershed • All these methods require cooperation with INCA analyzes of precipitation field and nowcasting and knowledge of antecedent precipitation (API)

  16. CN method - estimate peak discharge We can use CN method to determine the peak discharge for relatively homogeneous watersheds ASSUMPTIONS: We shouldn´t use this method for runoff amount < 38 mm CN < 60 -Tc time of concentraction < 10 hours

  17. We need folloving inputs: • A - area of watershed (in square km) • determine antecedent moisture conditions (I,II,III) • determine CN (I,II,III) • estimate Tc – watershed time of concentration (in hours) • determine potential max storage A • determine initial abstraction IA IA = 0,2*A if IA >P then rainfall event wouldn´t produce runoff

  18. P - total amount of precipitations • determine the accumulate runoff -determine the unit peak discharge coefficients c0,c1,c2 are estimated with regard to IA/P (see in following table) if IA/P is outside the bounds of table, use more precise method (for example HEC-HMS)

  19. determine the pond adjustment factor F as follows: coefficients c0,c1,c2 are estimated with regard to IA/P (see in following table) if IA/P is outside the bounds of table, use more precise method (for example HEC-HMS) compute the peak discharge:

  20. where: Q = peak discharge (m3/s) qu= unit peak discharge (m3/s/km2/mm) A = drainage area (km2) R = runoff (mm) F = ponding factor We use this method for basin Handlovka for flash flood 14.6.2007 The results:

  21. For basin Gidra: Flashflood 7.6.2011 (Precipitation amount from INCA analyse 85,9 mm)

  22. Operative system of flash flood forecasting • Based on analyses of precipitation field and on nowcasting of precipitation • Covering of layer of precipitation and layer with CN method • Simple program for computing flood peaks • 2012 summer storm season – calibration period • Output in the form of ansambel forecast • Necessarity of trainings for stakeholders

  23. Thank you for attention

More Related