Flood Risk Analysis of Ganges BasinThesis Student: Mufazzal Hossain Registration Number: 09205046

Flood Risk Analysis of Ganges Basin

Introduction Literature Review and Methodology

Data Analysis and Discussion

Conclusion and Recommendation

Introduction: Background Flood in the Past:

Lesser population in the floodplain

Lesser development in the floodplain

More benefits than risks Social Benefit Economical Benefit Environmental and

Agricultural Benefit

Flood in the Present: With time floodplain

population has increased. Amount of development has

increased in floodplain. Risks started to become more

visible than benefits. Some response and

prevention measures are: Structural Defenses Upstream Storages Land-use Controls

To calculate the discharge by flood frequency analysis, generate hydrographs by using the concept of synthetic unit hydrograph for 5, 10, 15, 25, 50 and 100 years return period.

Calculate the probability of occurrence at least once of such floods within 2063.

To identify the various risks such floods poses in the study area. To present the flood effect mitigation measures and emergency

response for planning purpose at the study area.

Introduction: Objectives

Introduction to Ganges Basin

Figure: Ganges, Brahmaputra & Meghna River Watershed (Rahaman, 2006)

Literature Review and Methodology

Flood Risk Analysis can be defines as the process of analyzing the risk due to flood in order to find out the probable impact level and then preventing irreversible changes and mass damages from happening or mitigate with the adverse impacts.

Flood Risk Analysis

Literature Review and Methodology

Determine the Causes of Flood

Risk Based Approach to

Flood Management

Reviewing the Strategy and

Policy Framework

Flood Risk Assessment and

Mapping

Planning and Development

Protecting Communities in

Floodplain

Defending Individual Properties by

Resistance and Resilience

Forecast and

Warning Systems

Flood Response and Recovery Insurance

Funding to Support Flood Risk

Analysis and Management

Protecting Communities at

Risk in the Longer Term

Literature Review and Methodology

Methodology

Data Analysis Methods

Rational Method

Flood Frequency Analysis

Snyder’s Synthetic Unit Hydrograph

Risk Analyzing Methods

Risk Identification Method

Risk Rating Method

Risk Level Determining Method

According to the Royal Academy of Engineering of United Kingdom, the Prevention and Emergency Response Measure can be implemented in the 5 following ways. Avoid Reduce Mitigate Transfer Do Nothing

Prevention and Emergency Response

Literature Review and Methodology

Data Analysis and Discussion

1 10 10018,000,000,000.0019,000,000,000.0020,000,000,000.0021,000,000,000.0022,000,000,000.0023,000,000,000.0024,000,000,000.0025,000,000,000.00

f(x) = 2233203565.957 ln(x) + 16669474605.17R² = 0.999826155803164

Gumbel’s Probabil-ity Paper

Return Period (T)Dis

char

ge, Q

(m

3/Fl

ood

perio

d)Return Period in

YearsDischarge (m3/Flood

Period)

5 20,240,964,312

10 21,835,839,289

15 22,735,654,274

25 23,365,681,657

50 27,824,046,011

100 29,210,340,372

Discharge Frequency Curve Calculated Discharge for Different Return Period

Data Analysis

0 100 200 300 4000

100000200000300000400000500000600000700000800000900000

1000000

Flood Hydrograph for the Return Period of 5 YearsFlood Hydrograph for the Return Period of 10 YearsFlood Hydrograph for the Return Period of 15 YearsFlood Hydrograph for the Return Period of 25 YearsFlood Hydrograph for the Return Period of 50 YearsFlood Hydrograph for the Return Period of 100 Years

Time (Hours)Dis

char

ge, Q

(m3 /s

)

Hydrograph for Each Return Period

Data Analysis and Discussion

Data Analysis

Flood Events Probability

5 Years Return Period Flood 1

10 Years Return Period Flood 0.99

15 Years Return Period Flood 0.96

25 Years Return Period Flood 0.87

50 Years Return Period Flood 0.64

100 Years Return Period Flood 0.39

Probability of Various Flood Events

Data Analysis and Discussion

Data Analysis

RiskLikelihood Consequences Risk

RatingCategory Level Description Category Level Description

Damage of Houses and Household Products A 6 Likely II 5 Major 30

Inundation of Road Networks and Their

Damage & DestructionA 6 Likely II 5 Major 30

Damage of Crops and Losses of Live Stocks A 6 Likely III 4 Serious 24

Erosion of Agricultural Land and Problems in Relocation of People

A 6 Likely I 6 Catastrophic 36

Spread of Diseases and Affect on Health A 6 Likely I 6 Catastrophic 36

Risk Rating Table

Data Analysis and Discussion

Risk Analysis: Risk Rating

Risks Risk Rating Risk Level Color CodeRemarks on Prevention and

Emergency Response Measures

Damage of Houses and Household

Products30 High Red

Requires emergency prevention measures,

mitigation and management measures, evacuation of people along with food

supply and treatment facility supplies.

Inundation of Road Networks and Their

Damage & Destruction

30 High Red

Damage of Crops and Losses of Live

Stocks24 High Red

Erosion of Agricultural Land and Problems in

Relocation of People36 High Red

Spread of Diseases and Affect on Health 36 High Red

Risk Analysis: Risk Leveling and Remarks

Risk Level of Identified Risk and Remarks

Data Analysis and Discussion

Current Mitigation Measures Structural Mitigation

Non-Structural Mitigation

Legislation, Policy and Planning

Training & Public Awareness

Institutional Arrangements

Warning Systems

Local Disaster Action Plans

Coordination Mechanism

Comprehensive Disaster Management Program

Suggested Mitigation Measures Environmental Management

Mangrove Preservation

Afforestation

Waste Management

Water Resource Management Drainage

Rain Water Harvesting

Infrastructural Measures Road Networks

Building & Houses

Agricultural Mitigation Measures Mitigation Related to Fisheries

Development of Storm Resistant Boats

Conflict Resolution Between Shrimp & Rice Farmers

Discussion on Prevention & Emergency Response Measures

Data Analysis and Discussion

By using the flood frequency analysis the flood discharge for 5, 10, 15, 25, 50 and 100

years return period has be calculated to be 20.24 × 109 m3/Flood period, 21.84 × 109

m3/Flood period, 22.74 × 109 m3/Flood period, 23.37 × 109 m3/Flood period, 27.82 ×

109 m3/Flood period and 29.21 × 109 m3/Flood period respectively and by using the

synthetic unit hydrograph the peak discharge during each event has been calculated to

be 639775.8 m3/s, 690186.5 m3/s, 718627.8 m3/s, 753880.7m3/s, 879461.6 m3/s and

923279.5 m3/s respectively. The probability of the floods with the various return

period stated above has found to be 1, 0.99, 0.96, 0.87, 0.64 and 0.39 respectively. The

hydrographs was shown in slide 15.

The probability of the floods with the various return period stated above has found to

be 1, 0.99, 0.96, 0.87, 0.64 and 0.39 respectively.

Conclusion & Recommendation

The identified risks which is posed by various flood events are Damage of Houses and

Household Products, Inundation of Road Networks and Their Damage/Destruction,

Damage of Crops and Losses of Livestock and Spread of Diseases and Effects on

Health.

Suggested mitigation measures are Environmental Management, Water Resource

Management, Infrastructural Measures, Agricultural Mitigation Measures and

Mitigation Measures Related to Fisheries.

Conclusion & Recommendation

In order to make an improvement of this study one can do the followings,

Obtain the unavailable data & information and overcome the disadvantage of not

having high technological software.

By completing the Flood Frequency Analysis by Log-Pearson Type III distribution

and Log Normal Distribution for comparison with Gumbel’s Extreme-Value

Distribution method results

Conclusion & Recommendation

Recommendation