The document provides a comprehensive overview of flood forecasting, its importance in flood mitigation, and the methodologies used in Bangladesh and England & Wales. It emphasizes the need for accurate meteorological and hydrological data, as well as the significance of effective dissemination of warnings to the public. Challenges such as limited resources and data quality in Bangladesh highlight the complexities of implementing effective flood forecasting systems.

1. Presented By:
Group X
Shazzadur Rahman – 1116016
Abir Mohammad – 1116017
Sabiha Tabassum - 1116025
FLOOD FORECASTING
Presented To:
Dr. Md. Mostafa Ali
Associate professor,
Department of Water Resources
Engineering, BUET.

2. Overview
Introduction
Role of Flood Forecasting in Flood Mitigation
Design Considerations
Data Requirements
Flood Forecasting Methods & Models
Challenges in Bangladesh
Case Studies

3. Introduction

4. What is Flood Forecasting?
Flood forecasting is the use of forecasted precipitation and streamflow data
in rainfall runoff and streamflow routing models to forecast flow rates and water
levels for periods ranging from a few hours to days ahead.

5. What is Flood Warning?
Flood warning is the task of making use of these forecasts to make decisions about
whether warnings of floods should be issued to the general public or whether
previous warnings should be rescinded or retracted.

6. Relation Between Flood Forecasting and Flood Warning
Flood forecasting is the prerequisite for flood warning.
Flood warning is the outcome of flood forecasting.

7. Components of Flood Forecasting & Warning System
Collection of Real
Time Data
Preparation of
Forecast Warning &
Information Messages
Communication &
Dissemination of
Such Messages
Interpretation of The
Forecast & Flood
Observations
Response to The
Warnings
Review &
Improvement of The
System

9. Role of Flood Forecasting in Flood Mitigation

10. Prerequisite for successful mitigation of flood damage.
Can be effectively combined with other measures for flood prevention such
as retention, land use and structural measures, flood emergency and public
awareness.
Plays vital role in flood management when no preventive or defence
measures can be completely effective.
Increases flood resilience of the flood affected people.

11. Evacuation of Vulnerable Groups And Moving of Assets
Shelter

12. Installation of Flood Resilience Measures (e.g. Sandbags, Property Flood Barriers)

13. Temporary Flood Defence

16. Design Considerations

17. Basic Consideration
Hydromorphological Characteristics of The Basin, Topography, Geology
Shape, Boundaries And Content of A
Water Body.

18. Main Physical Processes Occurring During Hydrometeorological Events

19. The Type of Service That is Required or Can be Achieved Technically And
Economically
Threshold-based flood alert: qualitative estimation of the increase in river flow or level
Flood forecasting: more definitive service based on the use of simulation tools and modelling
Vigilance mapping: development of the site-specific warning approach
Inundation forecasting: It requires the combination of a hydrological or hydrodynamic level-and-flow
model with digital representation of the flood plain land surface

20. Forecast Lead Time
Basic Principle: minimum period of advance warning necessary for preparatory
action to be taken effectively
Concept of lead time has to be flexible

21. DATA REQUIREMENTS

22. Hydrological data
Meteorological data
Topographic data
Other information and data

23. Hydrological Data
Discharge & Water level

24. Stream Gauge

25. Meteorological data
Rainfall intensity and duration,
precipitation forecasts and past data

26. RAINGAUGE

27. 56 Raingauge stations
of Bangladesh

28. Rainfall Measurement Using Radar

29. Topographic data
Information about the elevation of
the surface of the Earth

30. Topographic map of
Bangladesh

31. DEM of Bangladesh

32. (a) Population and demographic data to indicate settlements at risk;
(b) Inventories of properties at risk;
(c) Reservoir and flood protection infrastructure control rules;
(d) Location of key transport, power and water supply infrastructure;
(e) Systematic post-flood damage assessments.
Other information and data

33. FLOOD FORECASTING METHODS AND
MODELS

35. The “multi-model” approach to rainfall–runoff modelling and forecasting

37. SPECIAL-CASE MODELS
Storm surge
Two types of models, statistical and dynamic, can be used to forecast storm surges
Flash floods
distributed hydrological models
Urban Flooding
very high spatial and temporal resolution in data, models
Reservoir flood control
Estimates incoming flood and incorporates it with d/s riparian area

38. Examples
MIKE FLOOD
Delft-FEWS

39. MIKE FLOOD
Includes 1D and 2D flood simulation engines
model any flood problem
three-way coupled modelling tool
MIKE HYDRO River + MIKE URBAN + MIKE 21

40. Delft-FEWS
provide an open shell for managing
the data handling and forecasting
process

42. In Bangladesh, FFWC
• uses GIS techniques extensively to display water level and
rainfall status
• flood forecast model MIKE 11 FF

43. LIMITATIONS
• not sufficient on its own to reduce risk
• Models require continuous improvisation (calibration)
• Cost of running the system
• Cost of sourcing meteorological data
• system inaccuracies may lead to complacency
• availability of communication channels requires resource

44. Challenges in Bangladesh

45. Data Collection
57 transboundary river
Location of Bangladesh in GBM
basin

48. Tidal Influence on River
Uncertainty in Forecast of Rainfall

49. Other Challenges
Limited Resource
Limited Skilled Manpower

50. Case Studies

51. Case Study: BANGLADESH

52. Study Area: Bangladesh
Performed by: FLOOD FORECASTING & WARNING CENTRE (FFWC) of BWDB
Model Based on: MIKE11 FF conceptual Hydrodynamic model
DEM Used: 300m SRTM

53. Objectives of FFWC
 Forecasting: Predicts the occurrence/magnitude of flood.
 Interpretation: Warn people about the extent of flooding.
 Dissemination: Communication/distribution of warning messages to
disaster management agencies & vulnerable communities.
 Response: Preparation/action by concerned agencies and threatened
communities for protection against flood hazards.
 Review & Analysis: Continuous monitoring of the performance of the
various components.

54. Stations
WL STATIONS = 95 (50 Rivers)
Brahmaputra
Basin(35
Stations)
Ganges
Basin(25
Stations)
Meghna
Basin(27
Stations)
South Eastern
Hill Basin(8
Stations)
Rainfall Stations: 56

56. Overview of Flood Forecasting
Indian Data
WMO
JRC
WARPO
F F WC R a d io To we r
FFWC Satellite dish
24, 48, 72 hr
forecasts
water level
flood extent
m aps
thana
inundation
m aps
Telephone
Fax
Fax Modem
Modem
Telev ision
Bulletine
GIS data lay ers
Radio
wirelesscommunication
via modem
manual entry
Telemetry/Databox/Voice
SPARRSO
Sattelite images
BMD
Weather f orecast
Sy noptic charts
Boundary estimation
Rainf al,
Water lev el
Data Entry & Processing Modelling & Mapping
R iv er stage
R ainf all
R
e
a
l
T
i
m
e D a t a
D i s s e m i n a ti o n
t o th e pu bl i c
D i s s e m i n a t i o n
t o va ri o u s a g e n c i e s
Internet

57. Data Entry & Retrieval System

61. Water Level Status shown in FFWC Website

62. Types of Flood Forecasting
Probabilistic Method (10 days)
Deterministic Method (5 days)

63. FLOOD FORECAST EVALUATION, 2014
EVALUATION CRITERIA OF FLOOD FORECAST PERFORMANCE:
Two statistical criteria considered:
 Mean Absolute Error, MAE
 Co-efficient of Determination, r2
MAE: Mean of absolute difference between Observed and Forecast levels.

64. r2: Co-efficient of Determination for the correlation of Observed and Forecast water
levels.

65. PRE-DEFINED SCALES TO EVALUATE
FORECAST PERFORMANCE

66. Simulations were made for maximum 120 hrs.
Flood Forecast generated at 54 stations/points.
For 1-day forecast 98.15% for the stations are within
the range of Good and Average.
For 5-days forecast 59.26% stations are in the range of
Good and Average.
Deterministic Forecast Performance (2014)

69. Weaknesses
 Estimation of upstream inflows from India
 Quality of the data
 Inadequate rainfall radar stations
 Flood mapping accuracy limited by DEM resolution of 300m
 Modest investment in software and staff resources
 Upstream boundary estimation
 Lack of integration between the organizations
 Forecast lead time 3-5 days, for rural areas to support
agricultural activities, long term forecasts needed.

70. Case Study: ENGLAND & WALES

71. Study Area: England & Wales
 Performed by: Flood Forecasting Centre (FFC), a partnership between the
Environment Agency & the Met Office.
Separate operational forecasting rooms in each of the eight Environment
Agency Regions.
 Warning Time: 30 minutes to 72 hours.

72. Objectives
 Monitoring of environmental variables that may lead to flooding
 Forecasting of possible flood
 Warning, in the sense of decision making when flooding risks are
realizable
 Dissemination of warning messages
 Response to the threat.

73. Monitoring Network
4500 locations across England.
 1100 Rain gauges
 1300 River flow
 2000 River level

74. Performance Evaluation (2013-14)
FIG: Flood Risk Matrix & Probability of Detection (Hits & Misses) for
2013/14

75. Coastal Flood Forecasting on 5 & 6 December,
2013
 The largest coastal flood for 60 years on the east coast and for 30 years on
the west coast.
 A deep Atlantic storm brought severe gale force winds with gusts up to
100mph forcing a huge surge down both the west and east coasts of the UK.
 Increased WL & wave heights over three successive tides starting on the
afternoon of Thursday, 5 December until Saturday, 7 December.

76.  Potential surge was first spotted 7 days ahead.
 The risk level in the Flood Guidance Statement was escalated during
that week up to high likelihood of severe flooding (red).
 Government contacts & emergency responders were given good
notice of the developing situation.
 Coastal surge & wave models developed were hosted on the Met
Office supercomputer, helped inform critical decision-making.
 As the surge moved down the North Sea the FFC maintained a round
the clock commentary on live observations against the forecast.

77. How Flood Forecast Saves Lives
1953 2013
307 people dead No Death
24,000 properties flooded along the East
Coast.
Only one tenth of the level of property
flooding.

78. Thank You