DROUGHT AND FLOOD MANAGEMENT SCENARIO

IN INDIA

A.K. LOHANI

SCIENTISTEmail: lohani@nih.ernet.in

aklnih@gmail.com

akl_nih@yahoo.co.in

NATIONAL INSTITUTE OF HYDROLOGYROORKEE-247667

(UTTARAKHAND)

INDIA

• India is the most natural disaster prone area in the world.

• About 40 mha area of the country is flood prone and on average floods affect an area of about 7.5 mha

• About 153 mha are of the country is drought prone

• Every year country experiences these water extremes (floods and droughts) either on small or larger scale

FLOOD AND DROUGHTS

• The Ganga and Brahamputra are the chronic flood prone river basins

• The magnitude of precipitation over these basins is very high and more than three-quarters occurs during summer monsoon (June-Sept.).

• Natural hazards such as floods, droughts, earthquakes and cyclones affect an estimated 25 million people every year

• India accounts for nearly one-fifth of global death due to floods

Unlike other natural disasters, drought Unlike other natural disasters, drought does not have a clearly defined beginning does not have a clearly defined beginning

and end. As a result, our reaction to and end. As a result, our reaction to drought traditionally has not been timely.drought traditionally has not been timely.

DROUGHT

DEFINITIONS OF DROUGHT

• Meteorological droughtMeteorological drought

• Hydrological droughtHydrological drought

• Agricultural droughtAgricultural drought

DROUGHT PRONE AREASDROUGHT PRONE AREAS

 

Sl. No.

Meteorological sub-division Frequency of deficient rainfall

( 75% of Normal or less)

1 Assam Very rare, once in 15 years

2 West Bengal, Madhya Pradesh, Konkan, Bihar and Orissa

Once in 5 years

3 South Interior Karnataka, Eastern Uttar Pradesh and Vidarbha

Once in 4 years

4 Gujarat, East Rajasthan, Western Uttar Pradesh

Once in 3 years

5 Tamil Nadu, Jammu & Kashmir and Telangana

Once in 2.5 years

6 West Rajasthan Once in 2 years 

OBSTACLES TO EFFECTIVE OBSTACLES TO EFFECTIVE DROUGHT MANAGEMENT PLANNINGDROUGHT MANAGEMENT PLANNING

• Clarity About Beginning and End of Drought

• Randomness Associated with Drought

• Drought Phenomenon

• Economics of Droughts

• Social And Political Considerations

DROUGHT MANAGEMENT • Water Supply Conservation & Management

Measures • Water Demand Reduction and Management

Measures – Active demand reduction – Reactive demand reduction

• Water Conservation• Hydrological Preparedness for Impending Drought • Impact Minimisation • Efforts to Combat Desertification

DROUGHT MANAGEMENT

• Rehabilitation of Mined Aquifers • Research in Agro-meteorology • Remote Sensing and GIS Application for

Drought Management • Decision Support System in Drought

Management • Peoples Participation in Drought

Management

Contd...

DROUGHT MANAGEMENT Water Supply Conservation & Management Measures • Development of new water supply• Conjunctive Use• Agronomic, Soil& Water Conservation Measures• Watershed management• Reservoir & Tanks• Inter basin water transfer• supply of treated domestic, Industrial and municipal

waste water• Artificial recharge• Rainwater harvesting

Contd...

DROUGHT MANAGEMENT Water Demand Reduction and Management Measures

– Active demand reduction – Reactive demand reduction

Active demand reductionActive demand reduction• Provision of legal restrictions• establishment of thresholds for short term

reduction to various users• Land use planning• Water pricing

– High beyond a prescribed limit– Incentives for using small amount of water

Contd...

DROUGHT MANAGEMENT

Reactive demand reductionReactive demand reduction

• Use of Recycling System

• Selection of Cropping Pattern

• Reduction in Urban water supply

• Water budgeting in Industries

Contd...

DROUGHT MANAGEMENT Water ConservationWater Conservation• Control of evaporation• Rain water Harvesting• Provision of water cisterns• Water conservation campaign

Contd...

DROUGHT MANAGEMENT

Hydrological Preparedness for Impending Hydrological Preparedness for Impending

Drought Drought

• Information on hydrological data

• System of hydrological monitoring to solve

drought problems

• Variability in the total amount of rainfall

• Variability in the total hydrologic process

Contd...

DROUGHT MANAGEMENT Impact MinimisationImpact Minimisation • Anticipating actions and decisions

before a drought actually occurs• Variation of soil moisture, fluctuation of

groundwater and streamflow• Prediction of soil moisture using

simulation model

Contd...

DROUGHT MANAGEMENT Efforts to Combat DesertificationEfforts to Combat Desertification• More than 1/3 of the total land area of globe is

prone to the hazards of desertification• In India arid zone covers about 12% of

country’s geographical area. – Rajasthan- 62%– Gujarat - 19%– Punjab & Haryana - 9%– Andhra Pradesh & Karnataka - 10%

• Special program launched since 1970-71

Contd...

DROUGHT MANAGEMENT

Rehabilitation of Mined Aquifers

• Control of GW withdrawal • Augmenting GW recharge

Contd...

DROUGHT MANAGEMENT

Research in Agro-meteorology• Need to give warning to farmers much in

advance regarding• seasonal variation in rainfall• rainfall distribution• climatic conditions & its variability

Contd...

DROUGHT MANAGEMENT

Remote Sensing and GIS Application for Drought Management

• RS & GIS based Drought Information System

• Development of Drought Indices

Contd...

DROUGHT MANAGEMENT

Decision Support System in Drought Management

• Using a DSS, a person responsible for the actual project is able to make rational use of the system without an in-depth knowledge of modelling techniques

Contd...

DROUGHT MANAGEMENT

Decision Support System in Drought Management

• used for timely recognition of onset of drought.• Identify area vulnerable to drought (in time domain).• Updated information on availability of water (surface &

Ground water) in space and time. • Suggest the actions required by decision makers

against the given scenario of drought condition.

Contd...

DROUGHT MANAGEMENT

Peoples Participation in Drought Management

• Involve common people• Provide incentives• Role of NGO’s

Contd...

FLOODS IN INDIA

• Most frequent and devastating natural disaster• Frequent with varying magnitude• Hydro-meteorological conditions

– Monsoon during four months

• Flood risk to unprotected as well as protected areas

• Flood Prone Area - 40 m.ha(as per Rashtriya Barh Ayog)

- 45.64mha (as reported by the States to the

working Group for tenth plan)

FLOOD PRONE REGIONS IN INDIA

• Brahmaputra River Region

• Ganga River Region

• North West River Region

• Central India and Deccan Region

FIVE MAJOR FLOOD PRONE STATES IN INDIA

(As reported in RBA report)

• ASSAM

• BIHAR

• WEST BENGAL

• UTTAR PRADESH

• ORISSA

States Mostly Affected By Floods

13.910.4

31.5

16.36

42.6

29.49

8.7

0.64

14

4.8

73.36

16.02

26.5

22.66

0

10

20

30

40

50

60

70

80

AndhraPradesh

Assam Bihar Kerala Orissa UttarPradesh

WestBengal

Flood Prone Area as per RBA

Area Protected upto March2002

Lak

h

ha

DEFINITIONS OF FLOOD • Defining a flood is a difficult task

• Chow (1956) defined flood as, “a flood is a relatively high flow which overtakes the natural channel provided for the runoff”.

• Rostvedt and others (1968): Included artificial channels

• WMO(1978) : rise in the water level

• Dhar & Nandargi(1998): Flood when water level crosses danger level

CAUSES AND CONDITION OF CAUSES AND CONDITION OF FLOODINGFLOODING IN INDIAIN INDIA

• Very heavy local rainfall• heavy rainfall synchronizing with river spill;• cyclones; • Spilling of water from streams due to low carrying capacity • back water effect in tributaries when the main river carries

heavy discharge • landslides blocking in stream courses and ice jams resulting in

the back water overflowing river banks;• flooding in coastal area due to high tides; and inadequate

drainage/ drainage congestion to carry away surface water with the desired quickness etc.

• flooding due to the failure of flood control structures.

TYPES OF FLOOD

• Flash floods

• Single event floods

• Multiple event flooding

• Seasonal floods

• Dam break floods • Floods due to drainage

congestion

FLOOD PROBLEMS IN INDIA

• about 41 million hectares, or nearly one eighth is considered flood prone

• about 8.6 M ha of land area is annually affected

• average annual damages of the order of Rs.2,500 Crores

CHRONIC FLOOD PRONE BASINS: a) GANGA b) BRAHMAPUTRA

FLOODING IN HIMALAYAN RIVERS DUE TOHIGH DISCHARGE DURING MONSOON MONTHS

DEPOSITION OF SEDIMENTS CAUSE: a) RISE IN RIVER BED b) REDUCES CHANNEL CARRYING CAPACITY

FLOODS ASSOCIATED WITH CYCLONES AS INGUJARAT, ORISSA AND A.P.

AREA SUSCEPTIBLE TO FLOOD DAMAGE: in 1960 ~ 19 M ha in RECENT TIMES ~ 59 M ha

POSSIBLE REASONS a) URBAN & INDUSTRIAL EXPANSION b) DEFORESTATION c) OVEREXPLOITATION & MISUSE OF CATCHMENTS CAUSING LOW WATER RETENTION AND INCREASED RUNOFF d) ENCROACHMENT IN FLOOD PLAINS

PAREECHU LANDSLIDE DAM

A major landslide in Tibetan Himalaya on the banks of Pareechu river created an artificial dam which build up an artificial lake of approx. 200 hectares & 60 m deep.

(Francis, S. et al, 2004, GIS Development)

More than 900 mm rainfall in a Day in Mumbai

MAGNITUDE OF FLOOD DAMAGES

Figure 1: Area affected (Thousnad Ha) due to floods during year 1953-2000

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MAGNITUDE OF FLOOD DAMAGES

Figure 2: Population affected Tthousand) due to floods during year 1953-2000

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MAGNITUDE OF FLOOD DAMAGES

Figure 3 : Human lives lost due to floods during year 1953-2000

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MAGNITUDE OF FLOOD DAMAGES

Figure 4:Total monetary damage (Rs. Cr.) due to floods during year 1953-2000

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CAUSES OF FLOOD IN THE

BRAHMAPUTRA VALLEY 1. PHYSIOGRAPHIC

CONDITION OF THE VALLEY

Width of the Brahmaputra river valley is only 80 to 90 km.

The river itself covers about 6 to 10 km in most places and in places even up to 18 km.

This condition lends it favourable for occurrence of frequent floods.

CAUSES OF FLOOD IN THE BRAHMAPUTRA VALLEY- contd.

2. Hydro-meteorological Conditions RAINFALL Heavy rainfall experienced every year due to south

west monsoon.

Annual rainfall ranges from 2480 mm to 6350 mm .

Rainfall is largely concentrated during 4 to 5 monsoon months is responsible for the floods in the valley.

The highest hourly rainfall recorded at Saralpara is 97.5 mm on 27.08.1977

3. Earthquakes and Landslides

The Brahmaputra basin lies in an area of acute seismic activity. (Zone – V).

The earthquakes of 1897 and 1950 are the most severe earthquakes.

3 m rise in the general low water level was observed at Dibrugarh.

The rise of bed level of Brahmaputra after the 1950 earthquake resulted in the development of a number of new spill channels on both banks

CAUSES OF FLOOD IN THE BRAHMAPUTRA VALLEY- contd.

CAUSES OF FLOOD IN THE BRAHMAPUTRA VALLEY- contd

5. ENCROACHMENT OF RIVERINE AREAS

Upto the 19th century, population was comparatively thin and human habitation was away from the river banks.

The population increased manifold during the 20th century resulting in encroachment of riverine areas.

Such encroachment decreased the waterway of river leading to spilling of banks and causing floods.

FLOOD MANAGEMENT AND CONTROL

• Structural Measures

• Non-structural Measures

FLOOD MANAGEMENT AND CONTROL

• Structural Measures– Reservoirs for the temporary

storage of flood waters– Embankments (dikes or levees) and

flood walls – The improvement of river channels

to enlarge their discharge carrying capacity

– Bypass and diversion channels to carry some of the excess flood water

NON‑STRUCTURAL MEASURES

Flood Forecasting

• Flood Magnitude and Lead Time

• Conventional Regression Method

• Rainfall-Runoff Models

• ANN

• Fuzzy Logic

Dam Break Flood Wave Simulation

• Predict Flood Characteristics: Peak Stage, Discharge, volume, flood wave, Travel Time

• Analysis is required for planning purpose

NON‑STRUCTURAL MEASURES...

Flood Inundation Mapping

– Remote Sensing & GIS Techniques• Reasonable good estimate• Timely information• Covers large area• Useful in planning purpose

NON‑STRUCTURAL MEASURES...

Flood plain Zoning

These provide information about:the areas to be inundated by floodsreturn periods of the floods depth of flooding over the flood

affected areas andthe risk associated with the flooding

NON‑STRUCTURAL MEASURES...

Flood Insurance– Most effective method to regulate the land uses

in the flood plain. – Insurance premium is charged depending upon

the nature nature and location of establishment– In India Scheme is not yet implemented

NON‑STRUCTURAL MEASURES...

DSS FOR REAL TIME FLOOD FORECASTINGDSS FOR REAL TIME FLOOD FORECASTING

•Data Aqusition System

•Input Processors

•Knowledge based real time flood forecasting system

• Output Processors

• Information Dissemination

NON‑STRUCTURAL MEASURES...

CONCLUDING REMARKS

• DROUGHT MANAGEMENT• Drought have Low priority• Drought Planning & Management schemes

– after persistence drought

• After normal rainfall rapid – decrease in drought planning schemes

• DSS at basin scale – outputs at Administrative scales

• People participation• Publication campaign

– Electronic & Print Media

CONCLUDING REMARKS

• FLOOD MANAGEMENT• Study of flood phenomenon• Study of Sediment Phenomenon• A combined approach considering

structural and non-structural measures• Use of GIS & RS• Need to develop a DSS• Need to improve cooperation &

coordination between different organisations

THANK YOU