# Flood Hazard and Natural Risk Assessment: A Case Study of Bangladesh

Polina Lemenkova

► To cite this version:

Polina Lemenkova. Flood Hazard and Natural Risk Assessment: A Case Study of Bangladesh. Doctoral. Course 24S796912 'Disaster Risk Management with Geoanalytics', Salzburg (Austria), Austria. 2024, pp.10. hal-04620677

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# Flood Hazard and Natural Risk Assessment: A Case Study of Bangladesh

Polina Lemenkova

<figure><img src="image_2.png" /></figure>

► To cite this version:

Polina Lemenkova. Flood Hazard and Natural Risk Assessment: A Case Study of Bangladesh. Doctoral. Course 24S796912 'Disaster Risk Management with Geoanalytics', Salzburg (Austria), Austria. 2024, pp.10. hal-04620677

HAL Id: hal-04620677

https://hal.science/hal-04620677v1

Submitted on 21 Jun 2024

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_3.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
# Flood Hazard and Natural Risk Assessment:
A Case Study of Bangladesh

## Assignment 4 for the Course 24S796912
'Disaster Risk Management with Geoanalytics'

Polina Lemenkova

Paris Lodron University of Salzburg, Department of Geoinformatics
Salzburg, Austria

June 7, 2024

## Introduction

Floods in the World

Floods in Asia

## Bangladesh

Factors of flood risks in
Bangladesh and Impacts of
Flood Hazards

Socio-Economic
Vulnerability

## Impacts of the Flood
Hazards in Bangladesh

Major Floods in Bangladesh

Mapping flood hazard and
shelter suitability in
Bangladesh

Mapping flood hazard in
Bangladesh using Deep
Learning

<figure><img src="image_2.png" /></figure>
# Flood Hazard and Natural Risk Assessment:
A Case Study of Bangladesh

## Assignment 4 for the Course 24S796912
'Disaster Risk Management with Geoanalytics'

Polina Lemenkova

Paris Lodron University of Salzburg, Department of Geoinformatics
Salzburg, Austria

June 7, 2024

## Introduction

Floods in the World

Floods in Asia

## Bangladesh

Factors of flood risks in
Bangladesh and Impacts of
Flood Hazards

Socio-Economic
Vulnerability

## Impacts of the Flood
Hazards in Bangladesh

Major Floods in Bangladesh

Mapping flood hazard and
shelter suitability in
Bangladesh

Mapping flood hazard in
Bangladesh using Deep
Learning

<figure><img src="image_4.png" /></figure>
# Floods in the world

Figure: Source: Dartmouth Flood Observatory. Global Active Archive of Large Flood Events, 1985-Present

<figure><img src="image_3.png" /></figure>

* Water is a resource but also can be a threat: flood risk management involves segments of water use (potable water, industrial use, irrigation, recreation, energy production)

* Flood risk analysis in terms of the risk equation: hazard, vulnerability, exposure and capacity.

* Flood correlates with large-scale events and climate change => multi-hazard scenarios.

* Flood reasons: heavy rainfall when land surface lacks the capacity to convey excess water.

* Flooding can also result from other phenomena, storm surge, tropical cyclone, tsunami, high tide.

* Flood types: riverine floods, flash floods, urban floods, glacial lake outburst floods and coastal floods (climatic and non-climatic processes cause these different types of floods)

* Globe coverage: Floods are the natural hazard with the highest frequency and the widest geographical distribution worldwide.

* Scale: although most floods are small events, monster floods are not infrequent.

* The human and economic losses caused by floods are impressive (Thousands of life losses + up to dozens of US $ billions)

## Flood Hazard and Natural Risk Assessment: A Case Study of Bangladesh

Polina Lemenkova

### Introduction

#### Floods in the World

Floods in Asia

#### Bangladesh

Factors of flood risks in Bangladesh and Impacts of Flood Hazards

Socio-Economic Vulnerability

### Impacts of the Flood Hazards in Bangladesh

Major Floods in Bangladesh

Mapping flood hazard and shelter suitability in Bangladesh

Mapping flood hazard in Bangladesh using Deep Learning

<figure><img src="image_4.png" /></figure>

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# Floods in the world

<figure><img src="image_5.png" /><figcaption>Figure: Source: Dartmouth Flood Observatory. Global Active Archive of Large Flood Events, 1985-Present</figcaption></figure>

* Water is a resource but also can be a threat: flood risk management involves segments of water use (potable water, industrial use, irrigation, recreation, energy production)

* Flood risk analysis in terms of the risk equation: hazard, vulnerability, exposure and capacity.

* Flood correlates with large-scale events and climate change => multi-hazard scenarios.

* Flood reasons: heavy rainfall when land surface lacks the capacity to convey excess water.

* Flooding can also result from other phenomena, storm surge, tropical cyclone, tsunami, high tide.

* Flood types: riverine floods, flash floods, urban floods, glacial lake outburst floods and coastal floods (climatic and non-climatic processes cause these different types of floods)

* Globe coverage: Floods are the natural hazard with the highest frequency and the widest geographical distribution worldwide.

* Scale: although most floods are small events, monster floods are not infrequent.

* The human and economic losses caused by floods are impressive (Thousands of life losses + up to dozens of US $ billions)

## Flood Hazard and Natural Risk Assessment: A Case Study of Bangladesh

Polina Lemenkova

### Introduction

#### Floods in the World

Floods in Asia

#### Bangladesh

Factors of flood risks in Bangladesh and Impacts of Flood Hazards

Socio-Economic Vulnerability

### Impacts of the Flood Hazards in Bangladesh

Major Floods in Bangladesh

Mapping flood hazard and shelter suitability in Bangladesh

Mapping flood hazard in Bangladesh using Deep Learning

<figure><img src="image_6.png" /></figure>

<figure><img src="image_7.png" /></figure>

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Floods in Asia

<figure><img src="image_24.png" /></figure>

The map shows the distribution of the major floods in Asia on the part of the International Federation of Red Cross and Red Cross Societies (IFRC) concerning the legal rights of a country or a nation.

Flood Hazard and Natural Risk Assessment: A Case Study of Bangladesh

Polina Lemenkova

Introduction

Floods in the World

Floods in Asia

Bangladesh

Factors of flood risks in Bangladesh and Impacts of Flood Hazards

Socio-Economic Vulnerability

Impacts of the Flood Hazards in Bangladesh

Major Floods in Bangladesh

Mapping flood hazard and shelter suitability in Bangladesh

Mapping flood hazard in Bangladesh using Deep Learning

► Flood magnitude depends on precipitation intensity, volume, timing and phase.

► Hydrogeological parameters increasing flood force: riverbed structure and drainage basins (frozen or not or saturated soil moisture or unsaturated) and status.

► Climatological parameters: precipitation (intensity and period), windstorms, storm surges and sea-level rise.

► Climate change has a prominent role when assessing flood risk

► Environmental factors increasing floods: deforestation, relief (topography),

► Human factors and interactions: collapsed dams and land-use activities such as urbanization which increases run-off volume and rate

<figure><img src="image_25.png" /></figure>

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# Bangladesh

<figure><img src="image_22.png" /><figcaption>Figure: Flood-prone regions of Bangladesh and areas vulnerable to flooding. Source: Based on BCA Drought Maps</figcaption></figure>

## Key points on Bangladesh:

* Bangladesh is among the countries that are the most affected by climate change

* Frequent natural disasters, loss of life, damage to infrastructure and economic assets, impacts on lives and livelihoods

* Floods, tropical cyclones, storm surges and droughts are likely to become more frequent and severe in the coming years

* Lies in the delta of three of the largest rivers in the world – the Brahmaputra, the Ganges and the Meghna

* Mostly low and flat topography, susceptible to river and rainwater flooding

* More than 50 million of people still live in poverty

* Many people live in remote or ecologically fragile parts of the country, e.g. river islands

* Approximately one quarter of the country inundated each year

* The poorest and most vulnerable living in the exposed areas suffer the most

* High population density and poverty

* Nature-dependant traditional agriculture

* Population at risk: elderly, women, disable, children and poor people

<figure><img src="image_23.png" /></figure>

## Flood Hazard and Natural Risk Assessment: A Case Study of Bangladesh

Polina Lemenkova

### Introduction

Floods in the World

Floods in Asia

### Bangladesh

Factors of flood risks in Bangladesh and Impacts of Flood Hazards

Socio-Economic Vulnerability

### Impacts of the Flood Hazards in Bangladesh

Major Floods in Bangladesh

Mapping flood hazard and shelter suitability in Bangladesh

Mapping flood hazard in Bangladesh using Deep Learning
# Bangladesh

<figure><img src="image_40.png" /><figcaption>Figure: Flood-prone regions of Bangladesh and areas vulnerable to flooding. Source: Based on BCA Drought Maps</figcaption></figure>

## Key points on Bangladesh:

* Bangladesh is among the countries that are the most affected by climate change

* Frequent natural disasters, loss of life, damage to infrastructure and economic assets, impacts on lives and livelihoods

* Floods, tropical cyclones, storm surges and droughts are likely to become more frequent and severe in the coming years

* Lies in the delta of three of the largest rivers in the world – the Brahmaputra, the Ganges and the Meghna

* Mostly low and flat topography, susceptible to river and rainwater flooding

* More than 50 million of people still live in poverty

* Many people live in remote or ecologically fragile parts of the country, e.g. river islands

* Approximately one quarter of the country inundated each year

* The poorest and most vulnerable living in the exposed areas suffer the most

* High population density and poverty

* Nature-dependant traditional agriculture

* Population at risk: elderly, women, disable, children and poor people

<figure><img src="image_41.png" /></figure>

## Flood Hazard and Natural Risk Assessment: A Case Study of Bangladesh

Polina Lemenkova

### Introduction

Floods in the World

Floods in Asia

### Bangladesh

Factors of flood risks in Bangladesh and Impacts of Flood Hazards

Socio-Economic Vulnerability

### Impacts of the Flood Hazards in Bangladesh

Major Floods in Bangladesh

Mapping flood hazard and shelter suitability in Bangladesh

Mapping flood hazard in Bangladesh using Deep Learning
# Factors of flood risks in Bangladesh

## Factors of risks in Bangladesh increasing vulnerability to flood hazards:

### ► Geographic location

* long coast line: floods more affect coastal and rural areas

* effect of saline water intrusion in the estuaries

* vast low-lying landmass

* extremely dynamic coastal geomorphological processes

### ► Socio-demographic and economic features

* Initial economic conditions (poor / non-poor)

* One of the poorest and the most flood-prone areas worldwide and in Asia

* Gender and general health condition (capacity to resist illnesses, stresses)

* Poorer segments of society live closer to the river: residents are mostly farmers cultivating rice, wheat, vegetables, oil seeds

### ► Environmental facts

<figure><img src="image_24.png" /></figure>

Bangladesh - one of the highest flood hazard area in the world;

<figure><img src="image_25.png" /></figure>

Location: coastal, Ganges River Delta, rural or urban

<figure><img src="image_26.png" /></figure>

Floods => reduced livelihood options, e.g. loss of agriculture, restriction of movement

<figure><img src="image_27.png" /></figure>

<figure><img src="image_28.png" /><figcaption>Flood in rural Bangladesh. Source: CNRS, Dhaka.</figcaption></figure>

In April 1991, a cyclone struck Bangladesh, claiming lives and leaving destruction in its path. The satellite image on top shows the eye of the catastrophic storm. The worst cyclone in recorded history on mortality count struck Bangladesh in November 1970.

Image source: NOAA

<figure><img src="image_29.png" /><figcaption>River Bank Erosion after Flood in Bangladesh.
Source: CNRS, Dhaka.</figcaption></figure>

## Flood Hazard and Natural Risk Assessment: A Case Study of Bangladesh

Polina Lemenkova

### Introduction

Floods in the World

Floods in Asia

### Bangladesh

Factors of flood risks in Bangladesh and Impacts of Flood Hazards

Socio-Economic Vulnerability

### Impacts of the Flood Hazards in Bangladesh

Major Floods in Bangladesh

Mapping flood hazard and shelter suitability in Bangladesh

Mapping flood hazard in Bangladesh using Deep Learning

<figure><img src="image_30.png" /></figure>
# Factors of flood risks in Bangladesh

## Factors of risks in Bangladesh increasing vulnerability to flood hazards:

### ► Geographic location

* long coast line: floods more affect coastal and rural areas

* effect of saline water intrusion in the estuaries

* vast low-lying landmass

* extremely dynamic coastal geomorphological processes

### ► Socio-demographic and economic features

* Initial economic conditions (poor / non-poor)

* One of the poorest and the most flood-prone areas worldwide and in Asia

* Gender and general health condition (capacity to resist illnesses, stresses)

* Poorer segments of society live closer to the river: residents are mostly farmers cultivating rice, wheat, vegetables, oil seeds

### ► Environmental facts

<figure><img src="image_42.png" /></figure>

Bangladesh - one of the highest flood hazard area in the world;

<figure><img src="image_43.png" /></figure>

Location: coastal, Ganges River Delta, rural or urban

<figure><img src="image_44.png" /></figure>

Floods => reduced livelihood options, e.g. loss of agriculture, restriction of movement

<figure><img src="image_45.png" /></figure>

<figure><img src="image_46.png" /><figcaption>Flood in rural Bangladesh. Source: CNRS, Dhaka.</figcaption></figure>

In April 1991, a cyclone struck Bangladesh, claiming lives and leaving destruction in its path. The satellite image on top shows the eye of the catastrophic storm.

The worst cyclone in recorded history on mortality count struck Bangladesh in November 1970.

*Image source: NOAA*

<figure><img src="image_47.png" /><figcaption>River Bank Erosion after Flood in Bangladesh.</figcaption></figure>

Source: CNRS, Dhaka.

## Flood Hazard and Natural Risk Assessment: A Case Study of Bangladesh

Polina Lemenkova

### Introduction

Floods in the World

Floods in Asia

### Bangladesh

Factors of flood risks in Bangladesh and Impacts of Flood Hazards

Socio-Economic Vulnerability

### Impacts of the Flood Hazards in Bangladesh

Major Floods in Bangladesh

Mapping flood hazard and shelter suitability in Bangladesh

Mapping flood hazard in Bangladesh using Deep Learning

<figure><img src="image_48.png" /></figure>
# Bangladesh: Socio-Economic Vulnerability

## Repeatability of hazards:

* Population suffered from devastating floods over the past 20 years in 1988, 1996, 1998 and 2004

* Indundation levels significantly higher for poorer households

* Impoverished face a higher risk of flooding and are more vulnerable

## Inequality of diverse social groups and their exposure to flood hazards:

* The higher the exposure level and income inequality, the less access to a natural resources

* Average damage costs and coping capacity higher for wealthier households

* Households with higher income take preventive measures and have significantly lower damage costs

* Unequal income distributions in villages with higher risk exposure

* The least well prepared at household- and community level face the highest risk of flooding

<table><caption>Table 2. Causes of Impacts, Vulnerable Areas and Impacted Sectors in Bangladesh:</caption><thead><tr><th>Climate and Related Elements</th><th>Critical Vulnerable Areas</th><th>Most Impacted Sectors</th></tr></thead><tbody><tr><td>Sea Level Rise and Salinity Intrusion</td><td>Coastal Area Island</td><td>Agriculture (crop, fisheries, livestock)<br>Water (water logging, drinking water)<br>Human settlement<br>Energy<br>Health</td></tr><tr><td>Floods</td><td>Central Region<br>North East Region Char land</td><td>Agriculture (crop, fisheries, livestock)<br>Water (urban, Industry)<br>Infrastructure<br>Human settlement</td></tr><tr><td>Temperature rise and drought</td><td>North-west</td><td>Agriculture (crop, livestock, fisheries)<br>Water<br>Energy<br>Health</td></tr></tbody></table>

## Introduction

Floods in the World

Floods in Asia

## Bangladesh

Factors of flood risks in Bangladesh and Impacts of Flood Hazards

Socio-Economic Vulnerability

## Impacts of the Flood Hazards in Bangladesh

Major Floods in Bangladesh

Mapping flood hazard and shelter suitability in Bangladesh

Mapping flood hazard in Bangladesh using Deep Learning

<figure><img src="image_31.png" /></figure>
# Bangladesh: Socio-Economic Vulnerability

## Repeatability of hazards:

* Population suffered from devastating floods over the past 20 years in 1988, 1996, 1998 and 2004

* Indundation levels significantly higher for poorer households

* Impoverished face a higher risk of flooding and are more vulnerable

## Inequality of diverse social groups and their exposure to flood hazards:

* The higher the exposure level and income inequality, the less access to a natural resources

* Average damage costs and coping capacity higher for wealthier households

* Households with higher income take preventive measures and have significantly lower damage costs

* Unequal income distributions in villages with higher risk exposure

* The least well prepared at household- and community level face the highest risk of flooding

<table><caption>Table 2. Causes of Impacts, Vulnerable Areas and Impacted Sectors in Bangladesh:</caption><thead><tr><th>Climate and Related Elements</th><th>Critical Vulnerable Areas</th><th>Most Impacted Sectors</th></tr></thead><tbody><tr><td>Sea Level Rise and Salinity Intrusion</td><td>Coastal Area Island</td><td>Agriculture (crop, fisheries, livestock)<br>Water (water logging, drinking water)<br>Human settlement<br>Energy<br>Health</td></tr><tr><td>Floods</td><td>Central Region<br>North East Region Char land</td><td>Agriculture (crop, fisheries, livestock)<br>Water (urban, Industry)<br>Infrastructure<br>Human settlement</td></tr><tr><td>Temperature rise and drought</td><td>North-west</td><td>Agriculture (crop, livestock, fisheries)<br>Water<br>Energy<br>Health</td></tr></tbody></table>

## Introduction

Floods in the World

Floods in Asia

## Bangladesh

Factors of flood risks in Bangladesh and Impacts of Flood Hazards

Socio-Economic Vulnerability

## Impacts of the Flood Hazards in Bangladesh

Major Floods in Bangladesh

Mapping flood hazard and shelter suitability in Bangladesh

Mapping flood hazard in Bangladesh using Deep Learning

<figure><img src="image_49.png" /></figure>
# Impacts of the Flood Hazards in Bangladesh

Impact of Event = Σ Intensity of Event * Σ Baseline Conditions * Σ Adaptive Capacity
In the coastal areas of Bangladesh communities are impacted by the following factors:

<figure><img src="image_32.png" /><figcaption>Destructions in Bangladesh after flood.</figcaption></figure>

Photo: Dev Sajid, Martin Isidore

Sasikar Maiti's, local estimator by OJK, source: www.ojk.org

<figure><img src="image_33.png" /></figure>

The Sunderbans - the world's largest tropical mangrove forests - is already losing islands from climate change impacts including coastal erosion and sea level rise. The forest has a unique ecosystem and rich in biodiversity.

<figure><img src="image_34.png" /></figure>

<figure><img src="image_35.png" /><figcaption>Flood in Bangladesh, June 11, 2007. Photo taken from http://www.bangladesh.gov.bd/press/press.html</figcaption></figure>

<figure><img src="image_36.png" /><figcaption>Udaya satellite in southern Bangladesh, Agrosofta et al. (2006)</figcaption></figure>

<figure><img src="image_37.png" /><figcaption>Flood in main road of Dhaka.</figcaption></figure>

Source: www.pofflet.net

<figure><img src="image_38.png" /><figcaption>Boats on a city road in Bangladesh.</figcaption></figure>

Source: CNRS, Dhaka.

<figure><img src="image_39.png" /><figcaption>Flood-prone area in Bangladesh, 1996</figcaption></figure>

## Flood Hazard and Natural Risk Assessment:

A Case Study of Bangladesh

Polina Lemenkova

### Introduction

Floods in the World

Floods in Asia

### Bangladesh

Factors of flood risks in Bangladesh and Impacts of Flood Hazards

Socio-Economic Vulnerability

### Impacts of the Flood Hazards in Bangladesh

Major Floods in Bangladesh

Mapping flood hazard and shelter suitability in Bangladesh

Mapping flood hazard in Bangladesh using Deep Learning

<figure><img src="image_40.png" /></figure>

<figure><img src="image_41.png" /></figure>

<figure><img src="image_42.png" /></figure>

<figure><img src="image_43.png" /></figure>

<figure><img src="image_44.png" /></figure>

<figure><img src="image_45.png" /></figure>

<figure><img src="image_46.png" /></figure>

<figure><img src="image_47.png" /></figure>

<figure><img src="image_48.png" /></figure>

<figure><img src="image_49.png" /></figure>

<figure><img src="image_50.png" /></figure>

<figure><img src="image_51.png" /></figure>

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<figure><img src="image_55.png" /></figure>

<figure><img src="image_56.png" /></figure>

<figure><img src="image_57.png" /></figure>
# Impacts of the Flood Hazards in Bangladesh

Impact of Event = Σ Intensity of Event * Σ Baseline Conditions * Σ Adaptive Capacity
In the coastal areas of Bangladesh communities are impacted by the following factors:

<figure><img src="image_50.png" /><figcaption>Destructions in Bangladesh after flood.
Photo: Dev Sajid, Martin Isidore
Source: Martin Isidore, a local artist by GOK, source: www.gok.org</figcaption></figure>

<figure><img src="image_51.png" /><figcaption>The Sunderbans - the world's largest tropical mangrove forests - is already losing islands from climate change impacts including coastal erosion and sea level rise. The forest has a unique ecosystem and rich in biodiversity.</figcaption></figure>

<figure><img src="image_52.png" /></figure>

<figure><img src="image_53.png" /><figcaption>Flood in Bangladesh, June 11, 2007. Photo taken from
http://www.rejoiceblog.com/2007/06/11/2007061107.html</figcaption></figure>

<figure><img src="image_54.png" /><figcaption>Udaya satellite in southern Bangladesh.
Agrodisc in (2006).</figcaption></figure>

<figure><img src="image_55.png" /><figcaption>Flood in main road of Dhaka.
Source: www.pofflet.net</figcaption></figure>

<figure><img src="image_56.png" /><figcaption>Boats on a city road in Bangladesh.
Source: CNRS, Dhaka.</figcaption></figure>

<figure><img src="image_57.png" /><figcaption>Flood-prone area in Bangladesh, 1996</figcaption></figure>

## Introduction

Floods in the World

Floods in Asia

## Bangladesh

Factors of flood risks in Bangladesh and Impacts of Flood Hazards

Socio-Economic Vulnerability

## Impacts of the Flood Hazards in Bangladesh

Major Floods in Bangladesh

Mapping flood hazard and shelter suitability in Bangladesh

Mapping flood hazard in Bangladesh using Deep Learning

<figure><img src="image_58.png" /></figure>

<figure><img src="image_59.png" /></figure>

<figure><img src="image_60.png" /></figure>

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# Impacts of the Major Floods in Bangladesh

Major floods in Bangladesh during the last 50 years and their consequences:

<table><thead><tr><td>Event</td><td>Impact</td></tr></thead><tbody><tr><td>1954 floods</td><td>Affected 55% of country</td></tr><tr><td>1974 flood</td><td>Moderately severe, over 2,000 deaths<br/>affected 58% of country<br/>followed by famine with over 30,000 deaths</td></tr><tr><td>1984 floods</td><td>Indurated 52,520 km²,<br/>cost estimated at US$ 378 million</td></tr><tr><td>1987 floods</td><td>Indurated over 50,000 km², estimated damage US$ 1.0 billion,<br/>2055 deaths</td></tr><tr><td>1988 floods</td><td>Indurated 61% of country,<br/>estimated damage US$ 1.2 billion,<br/>more than 45 million homeless,<br/>between 2,000-6,500 deaths</td></tr><tr><td>1998 floods</td><td>1,100 deaths,<br/>indurated nearly 100,000 km²,<br/>rendered 30 million people homeless,<br/>damaged 500,000 homes,<br/>heavy loss to infrastructure, estimated damage US$ 2.8 billion</td></tr><tr><td>2004 floods</td><td>Indurated 38%, damage US$ 6.6 billion, deaths 700,<br/>affected people nearly 3.8 million</td></tr></tbody></table>

General impacts of flood hazards on the population: Particular impacts of flood hazards on human health:

* temperature rise and widespread malnutrition (due to shortage of water)

* degrading water quality and quantity => illnesses: cholera, diarrhoea, dysentery, malaria, typhoid

<figure><img src="image_58.png" /></figure>

Flood Hazard and Natural Risk Assessment: A Case Study of Bangladesh

Polina Lemenkova

## Introduction

Floods in the World

Floods in Asia

## Bangladesh

Factors of flood risks in Bangladesh and Impacts of Flood Hazards

Socio-Economic Vulnerability

## Impacts of the Flood Hazards in Bangladesh

Major Floods in Bangladesh

Mapping flood hazard and shelter suitability in Bangladesh

Mapping flood hazard in Bangladesh using Deep Learning
# Impacts of the Major Floods in Bangladesh

Major floods in Bangladesh during the last 50 years and their consequences:

<table><thead><tr><td>Event</td><td>Impact</td></tr></thead><tbody><tr><td>1954 floods</td><td>Affected 55% of country</td></tr><tr><td>1974 flood</td><td>Moderately severe, over 2,000 deaths<br/>affected 58% of country<br/>followed by famine with over 30,000 deaths</td></tr><tr><td>1984 floods</td><td>Induced 52,520 km²,<br/>cost estimated at US$ 378 million</td></tr><tr><td>1987 floods</td><td>Induced over 50,000 km², estimated damage US$ 1.0 billion,<br/>2055 deaths</td></tr><tr><td>1988 floods</td><td>Induced 61% of country,<br/>estimated damage US$ 1.2 billion,<br/>more than 45 million homeless,<br/>between 2,000-6,500 deaths</td></tr><tr><td>1998 floods</td><td>1,100 deaths,<br/>induced nearly 100,000 km²,<br/>rendered 30 million people homeless,<br/>damaged 500,000 homes,<br/>heavy loss to infrastructure, estimated damage US$ 2.8 billion</td></tr><tr><td>2004 floods</td><td>Induced 38%, damage US$ 6.6 billion, deaths 700,<br/>affected people nearly 3.8 million</td></tr></tbody></table>

General impacts of flood hazards on the population: Particular impacts of flood hazards on human health:

* temperature rise and widespread malnutrition (due to shortage of water)

* degrading water quality and quantity => illnesses: cholera, diarrhoea, dysentery, malaria, typhoid

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Flood Hazard and Natural Risk Assessment: A Case Study of Bangladesh

Polina Lemenkova

## Introduction

Floods in the World

Floods in Asia

## Bangladesh

Factors of flood risks in Bangladesh and Impacts of Flood Hazards

Socio-Economic Vulnerability

## Impacts of the Flood Hazards in Bangladesh

Major Floods in Bangladesh

Mapping flood hazard and shelter suitability in Bangladesh

Mapping flood hazard in Bangladesh using Deep Learning
# Mapping flood hazard and shelter suitability in Bangladesh

<figure><img src="image_59.png" /><figcaption>Figure: Priority area for flood shelter construction based on the bivariate choropleth analysis</figcaption></figure>

## Hazard assessment:

* Flood hazard assessment includes inundation and flood hazard maps

* Different methodologies are needed to define flood hazard when different scales are considered

* ✓ Historic flood risk assessment: information on floods that have occurred in the past

* ✓ Predictive analysis assessing the areas that could be prone to flooding

* ✓ Modelling of the potential consequences

* ✓ Expert opinions: locals / departments / agencies to identify areas prone to flooding

* ✓ Probabilistic quantitative risk approaches and prognosis

* Heavy monsoon rainfall generates excessive flows in the rivers and causes floods almost every year

## Flood Hazard and Natural Risk Assessment: A Case Study of Bangladesh

Polina Lemenkova

### Introduction

Floods in the World

Floods in Asia

### Bangladesh

Factors of flood risks in Bangladesh and Impacts of Flood Hazards

Socio-Economic Vulnerability

### Impacts of the Flood Hazards in Bangladesh

Major Floods in Bangladesh

Mapping flood hazard and shelter suitability in Bangladesh

Mapping flood hazard in Bangladesh using Deep Learning

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# Mapping flood hazard and shelter suitability in Bangladesh

<figure><img src="image_90.png" /><figcaption>Figure: Priority area for flood shelter construction based on the bivariate choropleth analysis</figcaption></figure>

## Hazard assessment:

* Flood hazard assessment includes inundation and flood hazard maps

* Different methodologies are needed to define flood hazard when different scales are considered

* ✓ Historic flood risk assessment: information on floods that have occurred in the past

* ✓ Predictive analysis assessing the areas that could be prone to flooding

* ✓ Modelling of the potential consequences

* ✓ Expert opinions: locals / departments / agencies to identify areas prone to flooding

* ✓ Probabilistic quantitative risk approaches and prognosis

* Heavy monsoon rainfall generates excessive flows in the rivers and causes floods almost every year

### Introduction

Floods in the World

Floods in Asia

### Bangladesh

Factors of flood risks in Bangladesh and Impacts of Flood Hazards

Socio-Economic Vulnerability

### Impacts of the Flood Hazards in Bangladesh

Major Floods in Bangladesh

Mapping flood hazard and shelter suitability in Bangladesh

Mapping flood hazard in Bangladesh using Deep Learning

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# Mapping flood hazard in Bangladesh using Deep Learning

Reference: Lemenkova, Polina. 2024. "Deep Learning Methods of Satellite Image Processing for Monitoring of Flood Dynamics in the Ganges Delta, Bangladesh" Water 16, no. 8: 1141. DOI: 10.3390/w16081141

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Figure: Algorithms of Deep Learning by GRASS GIS for mapping flood hazards using satellite images

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Figure: Cartographic mapping of vulnerable area in Bangladesh by GRASS GIS

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# Mapping flood hazard in Bangladesh using Deep Learning

Reference: Lemenkova, Polina. 2024. "Deep Learning Methods of Satellite Image Processing for Monitoring of Flood Dynamics in the Ganges Delta, Bangladesh" Water 16, no. 8: 1141. DOI: 10.3390/w16081141

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Figure: Algorithms of Deep Learning by GRASS GIS for mapping flood hazards using satellite images

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Figure: Cartographic mapping of vulnerable area in Bangladesh by GRASS GIS

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