HYDROLOGICAL AND HYDRODYNAMIC ASSESSMENT OF KEDARNATH...
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HYDROLOGICAL AND HYDRODYNAMIC ASSESSMENT OF KEDARNATH FLOOD by N.N.Rai Director, Central Water Commission, India
Transcript of HYDROLOGICAL AND HYDRODYNAMIC ASSESSMENT OF KEDARNATH...
HYDROLOGICAL AND HYDRODYNAMIC ASSESSMENT OF KEDARNATH FLOOD
by
N.N.RaiDirector, Central Water Commission, India
Location Map
INTRODUCTION Kedarnath Shrine is situated at Lat
30.74 N and Long 79.06 E in Garhwalregion of Himalyas at an altitude ofabout 355o masl.
On 16 and 17th June 2013 heavy rainstogether with Chorabari glacial lakefailure caused flooding in Saraswatiand Mandakini rivers in Rudraprayagdistrict of Uttarakhand, India.
The observatory on Chorabari GlacierCamp (3820 masl) recorded 210 mmrainfall in 12 hours during 15th June2013 (5:00 PM) and 16th June 2013(5:00 AM). On 16 June 2013 from 5:00AMto 5:00PM 115 mm rainfall wasrecorded, total 325 mm rain in 24hours.
Spatial distribution of Rainfall
The India MeteorologicalDepartment (IMD) linkedheavy to very heavy rain-fall onthe higher Uttarakhand,Himachal and Nepal Himalayato the convergence of theSouthwest Monsoon troughand westerly disturbances,which led to the formation ofdense cloud over theUttarakhand Himalaya
16.06.2013Rainfall (mm)
17.06.2013Rainfall (mm)
Terrain around Kedarnath shrine
Event 1 On 16 June 2013 at 5:15PM, the torrential
rains flooded the Saraswati River andDudh Ganga catchment area, resulting inexcessive flow across all the channels.
The voluminous water studded withdebris from the surrounding regions andglacial moraines moved towardsKedarnath town, washing off upper partof the city (Sankaracharya samadhi,Jalnigam guest house, Bharat Seva SanghAshram,etc.) and leading to the biggestever devastation we have seen in theregion.
Due to heavy downpour, the town ofRambara was completely washed awayon 16 June evening.
Event 2 The second event occurred on 17
June2013 at 6:45a.m., after overflow andcollapse of the moraine dammedChorabari Lake which released largevolume of water that caused anotherflash flood in the Kedarnath townleading to heavy devastation inKedarnath and downstream vizRambara, Gaurikund, Sonprayag,Phata, etc.
Event-1: Flood Computations for 15-16 June 2013 Rainfall Total 24 hr rainfall – 325 mm Time Cum % of 24 hr rainfall Time Cum % of 24 hr rainfall
1 13 13 702 21 14 733 28 15 774 35 16 795 40 17 826 45 18 857 49 19 888 53 20 909 57 21 9310 60 22 9611 64 23 9812 67 24 100
0
10
20
30
40
50
60
70
80
90
100
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Cum
% o
f 24
hr r
ain
fall
Time (hour)
Kinematic Wave model for Flood ComputationRainfed CA at Rambara-50 sq.km, SF-14 sq.km
Peak discharge - 576 cumec, Effective 24 hr rainfall – 301 mm
Peak discharge - 576 cumec, Effective 24 hr rainfall – 301 mm
Peak discharge - 576 cumec, Effective 24 hr rainfall – 301 mm
River cross sections from Aster DEM
0 50 100 150 200 250 3003450
3460
3470
3480
3490
3500
3510
Ked Plan: Plan 01River = Mandakini Reach = 1 RS = 5000
Station (m)
Ele
vatio
n (m
)
Legend
Ground
Bank Sta
0 50 100 150 200 250 3003010
3020
3030
3040
3050
3060
3070
3080
Ked Plan: Plan 01River = Mandakini Reach = 1 RS = 2000
Station (m)
Ele
vatio
n (m
)
Legend
Ground
Bank Sta
0 50 100 150 200 250 3003340
3360
3380
3400
3420
3440
Ked Plan: Plan 01River = Mandakini Reach = 1 RS = 4000
Station (m)
Ele
vatio
n (m
)
Legend
Ground
Bank Sta
0 100 200 300 400 500 60038203840386038803900392039403960398040004020
KD Plan: River = Riverm and3 Reach = 3 RS = 1800
Station (m )
Ele
vatio
n (m
)
Legend
Ground
Bank Sta
0 100 200 300 400 500 6003500
3520
3540
3560
3580
3600
3620
KD Plan: River = Riverm and3 Reach = 3 RS = 199.9999
Station (m)
Ele
vatio
n (m
)
Legend
Ground
Bank Sta
Bed Profile of Mandakini river from Kedarnath complex to Rambara
0.0 50.0 100.0 150.0 200.0 250.0 300.0[meter]
2700.0
2710.0
2720.0
2730.0
2740.0
2750.0
2760.0
2770.0
2780.0
2790.0
2800.0
2810.0
[meter] MANDAKINI 4.800 6/15/2013 5:00:00 PM
Cross section of Mandakini river near Rambara
18:00:0015-6-2013
00:00:0016-6-2013
06:00:00 12:00:00 18:00:00 00:00:0017-6-2013
06:00:00 12:00:00
2694.5
2695.0
2695.5
2696.0
2696.5
2697.0
2697.5
2698.0
2698.5[meter] Time Series Water Level Water Level
MANDAKINI 4800.00
Rise in Water level at Rambara about 4.5 m, Flood peak velocity–8.5 m/s
Time series of Water level at Rambara
Time series of Water level at RambaraRise in Water level at Rambara about 4.5 m, Flood peak velocity – 8.5 m/s
18:00:0015-6-2013
00:00:0016-6-2013
06:00:00 12:00:00 18:00:00 00:00:0017-6-2013
06:00:00 12:00:00
2694.5
2695.0
2695.5
2696.0
2696.5
2697.0
2697.5
2698.0
2698.5[meter] Time Series Water Level Water Level
MANDAKINI 4800.00
00:00:0016-6-2013
12:00:00 00:00:0017-6-2013
12:00:001.0
1.5
2.02.5
3.0
3.5
4.0
4.5
5.05.5
6.0
6.5
7.0
7.5
8.0
[m/s] Time Series Flow velocity Flow velocityMANDAKINI 4650.00 Velocity
Time series of Velocity at Rambara
EmptiedChorabariLake
Chorabari Glacier
Breach Location
Breach Location of Chorabari Lake
Source: Bhuvan, NRSC, India
MIKE11 mathematical model setup for Glacial lake outburst flood
Bed Profile of river from Chorabari lake to Kedarnath
Bed profile
05:00:0017-6-2013
06:00:00 07:00:00 08:00:00
0.0
200.0
400.0
600.0
800.0
1000.0
1200.0
[m^3/s] Time Series Discharge DischargeLAKE 200.00
Chorabari lake outburst flood just d/s of lake locationBreach depth 20 m, Breach width (bottom) 40 m, side slope 0.75H:1VBreach development time : 10 minutes
05:00:0017-6-2013
06:00:00 07:00:00 08:00:00
0.0
100.0
200.0
300.0
400.0
500.0
600.0
700.0
800.0
900.0
1000.0
1100.0
1200.0
[m^3/s] Time Series Discharge DischargeMANDAKINI 1300.00
Lake outburst flood near Kedarnath complex
05:00:0017-6-2013
06:00:00 07:00:00 08:00:00
3528.5
3529.0
3529.5
3530.0
3530.5
3531.0
3531.5
3532.0
3532.5
3533.0[meter] Time Series Water Level Water Level
MANDAKINI 1400.00
Rise in water level near Kedarnath complex due to lake outburst – 4.5 m
As per reports water level rise at Kedarnath was about 5 m
05:00:0017-6-2013
06:00:00 07:00:00 08:00:00
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
[m/s] Time Series Flow velocity Flow velocityMANDAKINI 1400.00 Velocity
Lake outburst flood velocity near Kedarnath complex
05:00:0017-6-2013
06:00:00 07:00:00 08:00:00
0.0
100.0
200.0
300.0
400.0
500.0
600.0
700.0
800.0
900.0
[m^3/s] Time Series Discharge DischargeMANDAKINI 4650.00
Lake outburst flood hydrograph near Rambara
05:00:0017-6-2013
06:00:00 07:00:00 08:00:00
2694.5
2695.0
2695.5
2696.0
2696.5
2697.0
2697.5
2698.0
2698.5
2699.0
[meter] Time Series Water Level Water LevelMANDAKINI 4800.00
Rise in water level near Rambara due to lake outburst
05:00:0017-6-2013
06:00:00 07:00:00 08:00:00
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
10.0
[m/s] Time Series Flow velocity Flow velocityMANDAKINI 4650.00 Velocity
Lake outburst flood velocity near Rambara
Conclusion Due to saturated terrain condition because of continuous rain, only two
hours consecutive rainfall of intensity about 40 mm/hr was sufficientto create flash flood of the order of 600 cumec.
The average slope of the river from Kedarnath up to Rambara is about160 m/km, which created a shooting flood wave of 4.5 m deeptravelling with velocity of about 8.5 m/s, causing devastation ofRambara and some of the portions of Kedarnath on evening of 16th June2013.
The slope of hills near Kedarnath area is about 30 degree from verticalresulting time of concentration of about 1 hr only
The Chorabari lake outburst flood was about 1200 cumec, whichcaused sudden rise is water level by about 5 m near Kedarnath and 6 mnear Rambara. This flood wave translated with a shooting velocity ofabout 10 m/s, resulting complete devastation of Kedarnath, Rambaraand other locations.
Flood forecast constraints Every year lakhs of people visit Holy Kedarnath shrine
during Charodham yatra of Uttarkhand in India
This Yatra occurs when monsoon is also active in thispart of India, resulting flash floods in steep Himalayanterrain
For issuing advanced flood warning in steep hillyterrains of Himalayas, a reliable hourly/three hourlyrainfall forecast at least few hours in advance isessential, but the same is a major constraints atpresent.
Thank You
