This presentation is the part of 12-day (28 January–8 February 2019) training workshop on “Multi-scale Integrated River Basin Management (IRBM) from the Hindu Kush Himalayan Perspective” organized by the Strengthening Water Resources Management in Afghanistan (SWaRMA) Initiative of the International Centre for Integrated Mountain Development (ICIMOD), and targeted at participants from Afghanistan.

1. Training on Integrated River Basin Management
29 January, 2019
ICIMOD
Dr. Dilip K. Gautam
Flood Risk Management Specialist

2. Content
 Background
 Flood management practices
 Flood forecasting and early warning system
 Ways forward: Integrated Flood Management

3. Background
 The Terai of Nepal is the
alluvial and fertile plain
with elevation less than
300 m.
 About 50% of the total
population live in Terai.
 Every year, the Terai is
affected by monsoon
floods.
 Floods are recurrent
hazards in river valleys,
inner Terai and Terai of
Nepal.

4. Terai Flood 2017
 On 11-13 August, 2017, the Terai
region was hit by
unprecedented flood causing
significant loss of human lives,
assets and livelihoods.
 36 out of 77 districts affected,
18 of them severely
 About 1.7 million people
affected
 161 people died, 29 people
missing and 46 people injured
 More than 190,000 houses
destroyed or partially damaged
 Total damage USD 584.7
million, about 3% of GDP
 Glimpse of Terai Flood 2017
Source: PFRNA, 2017

5. Causes of Floods in Nepal
 Natural
 High intensity, continuous rainfall
 Glacial lake outburst
 Landslide dam outburst
 Non-natural
 Land degradation, soil erosion,
deforestation and unmanaged
agricultural practices resulting
siltation and rising of river bed
and banks
 Urbanization and other
development activities
 Increased exposure and vulnerability
 Congestion of urban drainage system
 Decreased infiltration, Increased
runoff
 Obstruction of natural drainage by
the embankments on the Indian
side of the border

6. What happens when there is
flooding?
 Flooding greatly increases the river’s energy so it can
do more work. The deeper and faster flowing river can
carry more load.
 Most rivers turn brown because of the large amount of
sediment carried in suspension.
 The amount of erosion carried out by hydraulic action
and abrasion is greatly increased.
 The sediments are deposited in the channel and flood
plain and the flood water overflows to the adjacent
areas causing damage to properties and destruction of
infrastructure.

7. Flood Management Practices
 Engineering approach = infrastructure to protect against floods
 Traditionally focused on flood control with structural measures such as
 embankments to better control streams and prevent flooding of land adjacent to a
river (may include bio-engineering works);
 solid spurs or groynes to deflect the flow away from the river bank;
 anti-flood sluices;
 check dams to control sediment transport
Embankment Spur

8. Flood Management Practices
 Limited, if any, consideration of alternative/ complementing solutions
such as :
 Green infrastructure (forests, vegetation engineering)
 Behavior change campaigns
 Institutional/management improvements
 Engineering Solutions Often Fail to Understand that:
 Flood issues have social, economic, environmental and institutional
dimensions that are inter-dependent
 Flood problems are complex, and sometimes “wicked” i.e. difficult to
formulate, evaluate and solve
 Past solutions may not replicate well and past conditions may not be good
predictions of future
 Flood Forecasting and Early Warning System and Community Based
Disaster Management are also gaining popularity in recent years.

9. Flood Forecasting and Early Warning System
 Flood forecasting and early warning system has been
proved an efficient and cost effective method for
minimizing the negative impacts of floods.
 The purpose of flood forecasting and warning is to
give advice about impending flooding so that people
can act to minimize the flood’s negative impacts.
Warning information should consists of
 Time of flood onset
 Magnitude of flood (water levels, discharges at key
locations)
 Location and extent of flooding
 Duration of flooding
 Likely impacts

10. Elements of Flood Forecasting
and Early Warning System
 Risk Assessment
 Real-time monitoring system
 Forecasting system
 Numerical Weather Prediction (NWP) system
 Data preprocessing system
 Hydrological modeling system
 Hydraulic modeling system
 Error correction system
 Warning system
 Web based Decision Support System (DSS)
 Dissemination and communication
 Preparedness and response
NMHS
NDMA

11. Elements of People Centered
End-to-End Early Warning System
Risk Assessment
•HVR assessment
•Target area
•Evacuation route
•Shelter
Monitoring
•Rainfall monitoring
•Water level monitoring
Dissemination and Communication
•Website of FFWC (Tables , Graphs, Bulletin)
•Newspaper
•Radio/TV
•Flags/Sirens/Phone/Mega-phone
Preparedness and Response
•First aid kits
•Foods, Water, Utensils
•Blankets
•boats, ropes, shelter
•alternate livelihood
People

Warning
•Warning formulation (Bulletin,
Advisory)
•Potential impact assessment
Forecasting
•Rainfall forecasting
•Flood level/discharge
forecasting

12. Risk Assessment
• Assessment of historical flood
depth, extent, duration
• Development of HVR map
• Assessment of local threshold
values for warning
• Assessment of lead time
• Identification of evacuation route
and shelter
• Participatory approach

13. Real Time Monitoring System
 Purpose
 to allow staff to monitor the situation in general terms;
 to give warnings against indicator or trigger levels for
rainfall intensity and/ or accumulation; and
 to provide inputs to forecast models, particularly for
rainfall–runoff models
 Components
 Sensors
 Data logger (DCP)
 Communication system
 Accessories (solar panel, battery, cables & connectors)

14. Real Time Monitoring System
Radar
Tipping bucket
Shaft encoder Bubbler
Staff gauges

15. Data Transmission System
VHF Radio at Station VHF Radio at Forecasting Center
Satellite
Mobile

16. Real Time Data Transmission System
Tipping Bucket Rain
gauge
Data
Wireless Connection
CDMA ModemData is stored in
the data logger
which is posted
in the server
through the
CDMA Modem
Getting the Data from the Rain Gauge
Database Server
Data
Wireless Connection
CDMA ModemData is stored in
the data logger
which is posted
in the server
through the
CDMA Modem
Water Level Sensor
Getting the data from the Water level sensor
Internet
Internet

17. Web Based Dissemination System

18. Numerical Weather Prediction System

19. Hydrological Model for Flood Forecasting
 Where, when, how large, how long ?
 Where will it flood?
 When will it flood?
 How large will the flood be?
 How long will the flood last?
 Simulated flow peaks, volumes and hydrographs at the
outlets of subbasins and the points of special interest
such as reservoirs, weirs or other hydraulic structures
 Simulated extent of flooded areas for different
precipitation events and various antecedent basin
conditions

20. Hydrologic processes that need to be
captured by the model
 Rainfall-runoff transformation
 Snow accumulation and melt
 Interception, infiltration, soil moisture accounting
 Evapotranspiration
 Regulated reservoir operation, diversion of flow

21. HEC-HMS Model for Narayani
 56 sub-basins
 Sub-basin created based on hydrometric stations.

22. Calibration Result at Devghat
Calibration Period: 2008 to 2011
Observed Precipitation Bias Corrected D1 Forecast Precipitation
Model Error Correction
Model Error Correction

23. Validation Result at Devghat
Validation Period: 2012 to 2013
Observed Precipitation Bias Corrected D1 Forecast Precipitation

24. Hydraulic Modelling using HEC-RAS
Geometric data preparation
• Devghat Hydrological
Station for Narayani and
Rajaiya Hydrological
station is taken as
Upstream Boundary
• Gandak Barrage at Indo-
Nepal Boarder is the
downstream Boundary
• 198 Cross Sections are
generated from the 30m
SRTM DEM

25. Hydraulic Modelling using HEC-RAS
Geometric data
preparation
• One Bridge of
600m width
digitized
• The ineffective
flow areas are
digitized to u/s
and d/s of the
bridge in both
banks

26. Inundation Map for Warning Level
7.5m for Narayani and 3m for East Rapti

27. Inundation Map for Danger Level
8.3m for Narayani and 3.4m for East Rapti

28. Inundation Map for 100 Year Flood

29. Dissemination Techniques
 Website
 E-mail
 SMS
 Voice Message Broadcast : TV,
Radio, mobile phones
 Newspaper
 Siren
 Megaphone etc.

30. Successful EWS
Warning received Warning understood and shared
Warning trusted and responded to

31. Community Based Disaster Management
 Active participation of people in each component
 Community empowerment to protect, prepare
themselves and make them resilient against the
disasters
 Government – NGO – Media- Community
Collaboration
 Formation of Community Based Organization
e.g. Disaster Management Committees

32. Ways Forward: Integrated Flood
Management
Flood Management in the context of
Integrated Water Resources
Management, aiming at:
 Sustainable development: balancing
development needs and flood risks
 Maximizing net benefits from floodplains:
ensure livelihood security and poverty
alleviation thereby addressing vulnerability
 Minimizing loss of life: in particular through
end-to-end FFEW Systems and
preparedness planning for extreme events
 Environmental preservation: ecosystem
health & services

33. IFM: Key Elements
 Adopting a mix of measures, both structural and
non-structural
 Managing the Water Cycle as a whole (flood/
drought, surface water/ground water)
 Integrating land and water management (river basin
as a planning unit, upstream-downstream linkage)
 Part of a Risk Management System adopting multi-
hazard approach (address all components of disaster
risk management)
 Participatory approach (community based disaster
risk management)

34. Flood Risk
 Hazard: probability of a particular
discharge or water level at a particular
place
 Exposure: Land and assets in the
inundation area of that flood
 Vulnerability: ability/disability of the
people or assets to withstand, cope with
or recover from the negative effects of
that flood
• Risk = Hazard x Exposure x Vulnerability

35. Measures for Risk Reduction
Reduce Hazard Reduce Exposure Reduce Vulnerability
 Retaining water where it falls
(increasing infiltration, rooftop
storing)
 Retention basins (natural wet
lands or depressions, man
made e.g., school play grounds,
household underground tanks
 Dams and reservoirs
 Diversion channel
 Land use management (e.g.,
house building codes in urban
areas, infrastructure building
practices, appropriate
landscape planning)
 Structural measures on the river
(Dykes, river training work such
as channelization, flood walls,
raised infrastructures such as
roads and railways)
 Structural and non-structural
measures/actions by individual
(flood proofing)
 Land regulation
 Flood emergency measures
(flood warning and evacuation)
 Physical: by improving the
infrastructure, well-being,
occupational opportunities and
living environment
 Constitutional: by facilitating
equal participation
opportunities, education and
awareness, providing adequate
skills and social support system
 Motivational: by building
awareness and facilitating self
organisation

36. Thank you for your attention!