Indo-US bilateral workshop onModeling and Managing Flood Risk in Mountain Areas

17-19 February 2015Lake Natoma Inn, Folsom, California

Floods in the Himalayas

RENOJ J THAYYENNational Institute of Hydrology, Roorkee

Flood regimes of Himalaya – Monsoon & Non-monsoon origin

Monsoon flood regime

Non- monsoon flood regime

Higher return periodHighly disastrous

Type of Floods in the Himalaya

Monsoon Floods

Torrential rain

Cloudbursts

Non-Monsoon Floods

Hybrid floods

Glacial Lake Outburst FloodGlacier surge dam burst Flood

Snow/Avalanche dams

Rain on SnowRain over Glacial lakes

Earth quake induced GLOFEarth bursts

Landslide Dams Outburst Flood(LDOF)

Floods Source Zones in the Himalaya

Monsoon peaks owing to steep orographic barriers

Bookhagen and Burbank, 2010

Monsoon and elevation depended water volumes

Peak flood72,727 m3/sec

(1962)

Peak flood~5000 m3/sec

(2014)Bookhagen and Burbank, 2010

Example - Flood Source zones- Chenab Basin

Out of 21 rain gauge stations in thebasin, 07 stations experienced highintensity precipitation whenever floodoccurred. The Paoni station recordedhighest intensity rainfall all the time.

Paoni

Flood Impact zones in the Himalaya

1st & 2nd order streams & valley slopes in the source zone experience upstream

flooding. Frequent occurrence across the

region.

Main river at the foothill zone experience

downstream flooding

Relatively safer main stream flowing in the

deep valleys 2014 2012

20131994

2012

Maximum observed discharge at Pandu (on 23.8.1962) 72,727 m3/sec Minimum observed discharge at Pandu (on 20.2.1968) 1,757 m3/sec Average dry season discharge at Pandu 4,420 m3/sec

Kobo- 130 m a.s.l.Guwahati - 50.5 m a.s.l.

Flood impact Zone Brahmaputra River

Time of flood occurrence in different regions of Himalaya

Kashmir /JhelumMay - September

Great HimalayaJuly/August

Ladakh , July, August- CBAugust/ September, GLOF

StationPrevious Record 2014

All time records in 2014

Period 24 hrs(in mm) Date 24 hrs

(in mm) Date

Anantnag 1901-1982 149.4 01.09.1928 180 04.09.2014 All time record

Kukernagh 1979-2011 135.8 25.02.1987 149.5 05.09.2014 All time record

Qazi gund 1962-2013 160.9 09.09.1966 206 06.09.2014 All time record

Banihal 1962-2013 205.6 28.08.1997 188.8 05.09.2014 -

Batote 1979-2011 255.4 23.08.1996 208 05.09.2014 -

Katra 1980-2011 292.4 25.09.1988 279.2 04.09.2014 -

All-time record of 24 hours rainfall over J & K

All-time record of 48 hours cumulative rainfall over J & K

StationPrevious Record 2014 All time records

in 2014Period 48 hrs(in mm) Date 48 hrs

(in mm) Date

Anantnag 1901-1982 186.7 13.01.1903 238.4 03.09.2014 All time recordKukernagh 1979-2011 176.1 27.08.1997 268.9 04.09.2014 All time recordQazi gund 1962-2013 282.3 27.08.1997 362.7 05.09.2014 All time record

Banihal 1962-2013 310.4 18.02.2003 300.3 04.09.2014 -Batote 1979-2011 363.6 23.08.1996 331 05.09.2014 -Katra 1980-2011 418.4 22.08.1996 488.6 04.09.2014 All time record

StationPrevious Record 2014 All time records

in 2014Period 72 hrs(in mm) Date 72 hrs

(in mm) Date

Anantnag 1901-1982 210.8 16/09/1950 244.8 02.09.2014 All time record

Kukernagh 1979-2011 194.5 26.071995 357.5 04.09.2014 All time record

Qazi gund 1962-2013 300.7 17.02.2003 519.4 04.09.2014 All time record

Banihal 1962-2013 392.5 17.02.2003 389.3 03.09.2014 Near all time record

Batote 1979-2011 434 22.08.1996 433 04.09.2014 Near all time record

Katra 1980-2011 544.2 22.08.1996 698.6 04.09.2014 All time record

All-time record of 72 hours Cumulative rainfall over J & K

The Chong Kumdan Dam from the Lake. 12th August 1929.(Photo. F. Ludlow.)

Glacier Surge Dam- Chong Kumdan glacier Shyok River burst on 15 August 1929Followed by flood from torrential rains on August 25 1929 at lower reaches

Glacier surge dam burst Flood

June 2004 July 2009

September 2010

Mass gain ofKarakorum glacierscould resultsurging of someglaciers

Recent surge of Aktash Glacier, Shyok Valley

Landslide Dams Outburst Flood (LDOF)

A) Pareechu Landslide Dam Flood, June 25 2005

B) Bhagirathi River: Dabrani LDOF 6th August 1978C) Birahi Ganga (Alaknanda R.) 25-26 August 1894, Landslide 06 September 1893D) Alaknanda River 20 July 1970

Image courtesy, NASA

Rain on Snow + Lake burst floods 16-17 June 2013 Kedarnath, Uttarakhand

Earth Bursts, Baggi Village, UttarakhandAugust 15 2014

Photo: August 12 2014 Photo: Feb 06 2015

Rockfall +Avalanche +Friction melting of snow + Lake burst???Curious flood : Pokhara Flood May 05 2012

Bhandary et al.,2013

Some very recent Cloudburst Floods in the NWH Region

KedarnathRudraprayagAlmorahManaliLeh

Place Date Causality

Chirgaon, H.P August 15, 1997 1500

Gursa,Kullu, H.P July 16, 2003 40

Bhavi Village,H.P August 14, 2003 52+

Leh, Ladakh,J&K August 4-6 ,2010 255+

Almorah, H.P September 15 2010 Entire village

Manali, H.P July 20 2011 24

Assi Ganga, UK August 03, 2012 35+

Rudraprayag, UK September 13,2012 39+

Leh, Ladakh, J&K August 22,1933 (51.3 mm)

What we know about Cloudbursts?

Is extreme events are increasing in the Himalayan region ?????Is climate change playing any role ?????

According to the India Meteorological Department (IMD) acloudburst features very heavy rainfall over a localized area at avery high rate of the order of 100mm per hour ? featuring strongwinds and lightning. It is a remarkably localized phenomenonaffecting an area not exceeding 20–30 km2.?

Insights from Leh Cloudburst August 4-6 2010

Cloudburst floods along Ladakh Range

(Over a mountain ridge overlooking the NIH glacier camp)

Thayyen et al.,2013

Leh town area

Sabu Village Chonglamsar Village

(2.393km2 )(0.842 km2 )

(0.086 km2)

C3C2

C1Insights from Hydrological modeling –Leh Catchment

CB Impact area inthe catchment ~0.842 km2

Peak flood : Manning’s equationTime base : local Source

:SCS Dimensionless hydrograph: tp=d/2+ 0.6tc

Sampling strategy

Distinct geomorphic features of Cloudburst impact zone

Comparison of Atmospheric and Hydrological model results

Source Rain accumulation

Duration Peak flood (m3/sec) Area

Kristen et al 2012 Upward of 210 mm

03 hours

Kumar et al 2011 109.77 mm

195. 7mm

03 hours

06 hours

Anilkumar et al 2012 75 mm 01 hour

Thayyen et al 2013

Sabu E –T: 320±35%

Leh: 209±35%

~8.8 min

~11.9 min

Sabu : 1070±35%

Sabu E –T: 545±35%

Leh : 122±35%

64.95km2

2.83 km2

2.39 km2

Hobley et al 2012 142 mm 01 Hour Sabu -905 m3/sec

Return period >100yr ??

56.4 km2

1.601 km2

0.842 km2

209 (±35%) mm91.8 (±35%) mm

260(±35%)mm

320(±35%)mm

29.7 (±35%) mm

WRF model – 70mmIMD gridded rainfall – 120 mm

Sabu eastern catchment

Sabu catchment

Leh Town catchment

(2.393 km2)

(2.831 km2 )

(64.95 km2)

(9.0 km2 )

NCMRWF- 40 mm

Spatial controls of storm depth estimation & improvement made through hydrological modeling

Met.Station (12.8mm/day)

NIH Glacier camp(21.4mm/day)

August 06 2010

Limitations of point rainfall measuring station in recording CB’s

Stream/Catchment Year Date & Month

Leh Nalla (Ganglass) 2005 23/24 June

Phyang Nalla 2005 July

Leh Nalla(Gyalung Nalla) 2006 July

Phyang 2006 1st August 2006

Leh Nalla (Ganglass) & Igu

Nalla

2006 31st July& 1st

August 2006

Ulletop 2008 09 Aug

(Source: Office of the Tahsildar, Leh & I&FC, Leh)

Recent unrecorded CB events in Leh area

Giving life to past CB events

24 June 2005 06 July 2005 31 July 2006 01 August 2006

09 August 2008

Managing flood damage in the source area

Flood Hazard zonation, legislation & Habitat management

Leh Town

Chonglamsar, Leh

Kedarnath, Uttarakhand

Baggi village, Uttarakhand

Looking ahead……..

There are critical flood source zones in the Himalayas. Identifying thesesource zones are key to early flood warning , modeling and disaster riskreduction.

Lack of Inventory mechanism of extreme upstream flood events in theHimalaya (Cloudburst, Earth burst & GLOF) hamper the research on itscauses and solutions.

Post flood assessment is key to develop understanding of the floodgeneration mechanism especially of cloudburst and earth bursts due to itsspatial constraints. Methodologies required to be scaled for the Himalayanregion.

Flood hazard zone mapping combined with legislative intervention is key tothe flood management in the source zones whereas flood forecasting is keyto managing the downstream floods.

Negotiate fate vs planning

Thank you