This document provides an introduction to flood modeling. It discusses the different types of floods including river/fluvial floods caused by excessive rainfall, pluvial/surface floods from heavy urban rainfall, and coastal floods from extreme tidal conditions. It also describes how flood risk analysis uses modeling to support insurance schemes, simulate historical flood patterns, define risk zones and critical rainfall thresholds. The document outlines principal modeling approaches including hydrological models of water movement, hydraulic models of river/canal flow, and hydrodynamic models that simulate river flow in 2D or 3D. It discusses using decision support systems to manage data and models for planning and real-time applications like flood forecasting and early warning systems. Finally, it notes challenges like obtaining

1. Flood Modeling- An Introduction
Rajesh Kumar Mahana

2. Flood
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A flood is an overflow of water that
submerges land that is usually dry.

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4. Types of Flood
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 Fluvial (River Flood)
Excessive rainfall over an extended
period of time causes a river to
exceed its capacity (Overbank
Flooding & Flash Flooding)
Pluvial (Surface Flood/Urban
Flood)
Heavy rainfall creates a flood event
independent of an overflowing water
body
Coastal (Surge Flood)
Extreme tidal conditions caused by
severe weather

5. Flood Risk Analysis
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 Support design of an insurance scheme
 Simulate historical patterns of floods
 Define flood risk zones
 Define critical rainfall thresholds for floods
 Loss assessment with remote sensing
 Assess agricultural losses

6. Flood Modelling
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 Support design of an insurance scheme
 Simulate historical patterns of floods
 Define flood risk zones
 Define critical rainfall thresholds for floods
 Loss assessment with remote sensing
 Assess agricultural losses

7. Principal types of computer numerical models
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 Hydrological models
 Hydraulic models
 River basin planning models
 Hydrodynamic models
 Groundwater models
 Ecological models
 Other IT tools used in water resources planning
– Geographic Information Systems (GIS)
– Decision support and data management systems
– Cost-benefit and multi-criteria analysis tools

8. Hydrological Models
 Used to simulate movement of water through the hydrologic cycle
 Often used to simulate rainfall-runoff processes, including impacts
of land use change on runoff
 Also used to simulate surface water-groundwater interaction
 Sometimes used to simulate irrigation water use
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9. Hydraulic models
 Simulate flow of water in rivers and canals
 Also simulate alluvial floodplain processes
 Sometimes used to simulate water quality processes in rivers
 Also used for sediment transport modeling
 Can be integrated into hydrological models
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10. Hydrodynamic models
 In contrast to hydraulic models, simulate river flow in two or three
dimensions
 Used for detailed water quality and sediment transport studies
 Also used to simulate water quality and sediment transport
processes in lakes and reservoirs
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11. Decision support and data management systems
 Used to manage data and models
 Can be used in planning applications to develop different scenarios
of future conditions and facilitate comparison of model results
across scenarios
– Useful when there is uncertainty about future conditions
 Can be used in real-time applications as a centralized platform for
automating model runs and data management
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12. USE OF MODELS
 Planning applications
 Real-time applications
 Planning applications
– Long-term or seasonal time scales
– Used to support decision-making about infrastructure projects,
management policies, etc.
 Real-time applications
– Time scales ranging from minutes to days
– Used to support real-time operation of water management
infrastructure including dams and canals
– Also used to support warning systems, such as flood early-warning
systems
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13. Flood forecasting
 Real-time forecasts of river flooding are valuable for alerting
affected populations about flood events.
 Hydrological models can be used to forecast runoff if the catchment
area is large and there is a lag between rainfall events and
downstream runoff
 Hydrological models can also be used to forecast runoff in smaller
catchments if precipitation forecasts are available
 Hydraulic models can be used to forecast the extent of the
inundated area if runoff forecasts are available or if there is a lag
between runoff generation and downstream flooding
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14. Numerical Tools on Flood Modelling
 Open Source :
HEC-HMS, HEC-RAS, HEC-RTS, HEC-SSP, SWAT, ModFlow
 License:
Mike Suite, Deltares, Tuflow
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15. Flood Hazard Assessment
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16. Challenges
 Digital Terrain Data
 Hydro-meteorological and streamflow data
 Calibration and Validation
 Computation and Model Choice
 Flood Risk Zoning
– Design of an Insurance Scheme
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