Flash flood Flash flood forecasting in forecasting in

SlovakiaSlovakiaMichal HazlingerMichal Hazlinger

Slovak Hydrometeorological Slovak Hydrometeorological InstituteInstitute

Ljubljana 16.5.2012Ljubljana 16.5.2012

Input informations - Input informations - precipitationprecipitation

Problems with measurement – Problems with measurement – discrete raingauge stationsdiscrete raingauge stations

Problems with data gapsProblems with data gaps Automatic station network since 2004Automatic station network since 2004 Necessarity of spatial precipitation Necessarity of spatial precipitation

field – based on combination of radar field – based on combination of radar measurement and station data – INCA measurement and station data – INCA precipitation fieldprecipitation field

Input data in Myjava Input data in Myjava watershed and „Orava“ watershed and „Orava“

pilot basinspilot basins

INCA precipitation fieldINCA precipitation field

Forecast of runoffForecast of runoff

Hydrologic models - problems with Hydrologic models - problems with events with very short durationevents with very short duration

Testing of HBV variation for Slovak Testing of HBV variation for Slovak condition – HRONcondition – HRON

1 hour forecasting step1 hour forecasting step Calibrated for extreme events in 2011 Calibrated for extreme events in 2011

(Gidra basin) and 2010 (Oravica river (Gidra basin) and 2010 (Oravica river basin)basin)

Validation in 2010 resp. 2011 Validation in 2010 resp. 2011

Results of HRON Results of HRON simulation in Gidra river simulation in Gidra river

basinbasinRainfall input – APS and INCA Rainfall input – APS and INCA precipitation field analyzesprecipitation field analyzes

0

10

20

30

40

50

Q [

m3 s

-1]

0

5

10

15

20

25

30

35

40

P [

mm

]

PQobsQsim

Dispersion of simulated Dispersion of simulated and observed datasand observed datas

Calibration data set Validation data set

Hydrologic modelHydrologic model

Rainfall – runoff model HEC-HMSRainfall – runoff model HEC-HMSBasin model based on CN methodBasin model based on CN method for calibration used input data from raingauge for calibration used input data from raingauge stations (1 minute and 1 hour time step), from stations (1 minute and 1 hour time step), from watergauge stations and INCA precipitation field watergauge stations and INCA precipitation field (based on shp files, 5 min. time step, 1 x 1 km (based on shp files, 5 min. time step, 1 x 1 km spatial resolution)spatial resolution)

Calibration in Handlovka and Gidra river basinCalibration in Handlovka and Gidra river basinCalibrated for extreme eventsCalibrated for extreme eventsOutput - Hydrogram of outflow or possibility / Output - Hydrogram of outflow or possibility / propability of exceeding warning levelpropability of exceeding warning level

Hydrological modelsHydrological models Input from INCA precipitation field analyses Input from INCA precipitation field analyses

(based on *.shp, 5 min. timestep, 1 x 1 spatial (based on *.shp, 5 min. timestep, 1 x 1 spatial resolution)resolution)

HEC – HMS rainfall – runoff model – able to HEC – HMS rainfall – runoff model – able to compute runoff in small watershedscompute runoff in small watersheds

System based on estimation of flood potential by System based on estimation of flood potential by CN method – 3 states of saturationCN method – 3 states of saturation

Calibration results for Calibration results for Handlovka and Gidra river Handlovka and Gidra river

basinsbasinsWaveWavetime of time of

peakpeakpeak peak

flowflowvolumvolum

ee

RealReal 16:4516:45 44,544,5 410410

MinutovkMinutovkyy 16:4516:45 6262 538538

INCAINCA 17:0517:05 45,2045,20 315315

APS APS ModraModra 17:5017:50 48,848,8 383383

WaveWavetime of time of

peakpeakpeak peak

flowflow volumevolume

realreal 15:0015:00 8,68,6 85,2385,23

DryDry 15:4015:40 9,29,2 100,3100,3

AverageAverage 15:2015:20 99 93,393,3

SaturateSaturatedd 15:0015:00 25,925,9 276,3276,3

Gidra 7.6. 2011

WaveWavetime of time of

peakpeakpeak peak

flowflow volumevolume

realreal 14:0014:00 147147 33653365

DryDry 12:1512:15 51,151,1 547547

AverageAverage 12:4112:41 179,2179,2 23152315

SaturateSaturatedd 12:1812:18 298,4298,4 39583958

Handlovka 10.7. 2007

Handlovka 15.8. 2010

Case Study – Gidra (Píla)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

Calibration outputsCalibration outputs

Handlovka basin modelHandlovka basin model

Handlovka – calibration Handlovka – calibration and validation outputsand validation outputs

Other methods available Other methods available for flash flood for flash flood

forecastingforecasting3 different tools3 different tools

1. calibration of hydrological 1. calibration of hydrological models for various types of models for various types of watershed (based on natural watershed (based on natural condition) – weak coverage of condition) – weak coverage of SlovakiaSlovakia

2. estimation of flood potential - 2. estimation of flood potential - based on CN methodbased on CN method

3. estimation of flood potential – 3. estimation of flood potential – based on parameters of based on parameters of watershedwatershed

All these methods require All these methods require cooperation with INCA analyzes cooperation with INCA analyzes of precipitation field and of precipitation field and nowcasting and knowledge of nowcasting and knowledge of antecedent precipitation (API)antecedent precipitation (API)

CN CN method - estimate peak dischargemethod - estimate peak discharge

We can use CN method to determine the We can use CN method to determine the peak discharge for relatively peak discharge for relatively homogeneous watershedshomogeneous watersheds

ASSUMPTIONS:ASSUMPTIONS:

We We shouldn´tshouldn´t use use this method for this method for

runoff amount runoff amount < 38 mm< 38 mm

CN < 60CN < 60

-T-Tcc time of concentraction time of concentraction < 10 hours< 10 hours

We need folloving inputs:We need folloving inputs:-A - area of watershed (in square km)A - area of watershed (in square km)-determine antecedent moisture conditions (I,II,III)determine antecedent moisture conditions (I,II,III)-determine CN (I,II,III)determine CN (I,II,III)-estimate Tc – watershed time of concentration (in estimate Tc – watershed time of concentration (in hours)hours)-determine potential max storage Adetermine potential max storage A

-determine initial abstraction IAdetermine initial abstraction IA IA = 0,2*A IA = 0,2*A if IA if IA >P >P then rainfall event wouldnthen rainfall event wouldn´́t produce t produce runoffrunoff

10

1000*4,25

CNA

- P - total amount of precipitationsP - total amount of precipitations- determine the accumulate runoffdetermine the accumulate runoff

-determine the unit peak discharge-determine the unit peak discharge

coefficients c0,c1,c2 are estimated with regard to coefficients c0,c1,c2 are estimated with regard to IA/P (see in following table)IA/P (see in following table)

if IA/P is outside the bounds of table, use more if IA/P is outside the bounds of table, use more precise method (for example HEC-HMS)precise method (for example HEC-HMS)

)8,0(

)2,0( 2

SP

SPR

Rainfall Rainfall TypeType IIaa/P/P CC00 CC11 CC22

IIII 0.10.1 2.5532.55322

--0.6150.615

11

-0.164-0.164

   0.30.3 2.4652.46533

--0.6220.622

66

--0.1160.116

66   0.30.3

552.4192.419 --

0.6150.61599

--0.0880.088

22   0.40.4 2.3642.364

11--

0.5980.59866

--0.0560.056

22   0.40.4

552.2922.292

44--

0.5700.57011

--0.0220.022

88   0.50.5 2.2022.202

88-0.516-0.516 --

0.0120.01266

              IIIIII 0.10.1 2.4732.473

22--

0.5180.51855

--0.1700.170

88   0.30.3 2.3962.396

33-0.512-0.512 --

0.1320.13255

   0.30.355

2.3542.35488

--0.4970.497

44

--0.1190.119

99   0.40.4 2.3072.307

33--

0.4650.46544

--0.1100.110

99   0.40.4

552.2482.248

88--

0.4130.41311

--0.1150.115

99   0.50.5 2.1772.177

77-0.368-0.368 --

0.0950.09533

Ponding Adjustment Ponding Adjustment FactorFactor

% Ponded/Swamp % Ponded/Swamp AreaArea

FactoFactor (F)r (F)

00 110.20.2 0.970.9711 0.870.8733 0.750.7555 0.720.72

-determine the pond determine the pond adjustment factor F as adjustment factor F as follows:follows:

compute the peak compute the peak discharge:discharge:

coefficients c0,c1,c2 are estimated coefficients c0,c1,c2 are estimated with regard to with regard to IA/P (see in following table)IA/P (see in following table)

if IA/P is outside the bounds of table, if IA/P is outside the bounds of table, use more precise method (for example use more precise method (for example HEC-HMS)HEC-HMS)

where:where:QQ = peak discharge (m = peak discharge (m33/s)/s)qquu  = unit peak discharge (m= unit peak discharge (m33/s/km/s/km22/mm) /mm) AA = drainage area (km = drainage area (km22) ) RR = runoff (mm) = runoff (mm)FF = ponding factor = ponding factor

We use this method for basin Handlovka for flash flood We use this method for basin Handlovka for flash flood 14.6.200714.6.2007

The results:The results:Time of Time of concentrationconcentration

CCNN

QsimQsim QobsQobs

66 IIII 11,3011,30 9,8549,854

IIIIII 52,3352,33 9,8549,854

55 IIII 12,90712,907 9,8549,854

IIIIII 57,12757,127 9,8549,854

For basin Gidra:For basin Gidra:

Flashflood 7.6.2011Flashflood 7.6.2011

(Precipitation amount from INCA analyse 85,9 mm)(Precipitation amount from INCA analyse 85,9 mm)

Time of Time of concentrationconcentration

CNCN QsimQsim QobsQobs

55 IIII 28,228,2 44,544,5

IIIIII 71,1671,16 44,544,5

66 IIII 24,4824,48 44,544,5

IIIIII 61,9561,95 44,544,5

Operative system of flash Operative system of flash flood forecastingflood forecasting

Based on analyses of precipitation field and Based on analyses of precipitation field and on nowcasting of precipitationon nowcasting of precipitation

Covering of layer of precipitation and layer Covering of layer of precipitation and layer with CN methodwith CN method

Simple program for computing flood peaks Simple program for computing flood peaks 2012 summer storm season – calibration 2012 summer storm season – calibration

periodperiod Output in the form of ansambel forecastOutput in the form of ansambel forecast Necessarity of trainings for stakeholdersNecessarity of trainings for stakeholders

Thank you for Thank you for attentionattention