Project – Assessment of Urban Flood Vulnerability Using GIS and Remote Sensing in Selected Flood-Prone Areas of Lagos State

CHAPTER ONE

INTRODUCTION

1.1 Background of the Study

Flooding has become one of the most frequent and destructive natural hazards affecting urban centres across the world, especially in rapidly growing cities within developing nations. In recent decades, the increase in flood events has been strongly linked to climate change, poor urban planning, unregulated land-use conversion, and population growth in hazard-prone zones (Adelekan, 2016). Globally, urban flooding affects over 2.3 billion people annually, causing significant economic, social, and environmental losses (UNDRR, 2020). The situation is particularly severe in coastal cities where low-lying terrains, high rainfall intensity, and sea-level rise converge to intensify flood vulnerability.

Lagos State, Nigeria’s economic hub and one of the fastest-growing megacities in Africa, is extremely susceptible to recurrent flooding due to its unique physiographic and socio-economic characteristics. Approximately one-third of Lagos lies less than two metres above sea level, making many communities heavily exposed to storm surges, intense rainfall, overflowing drainage channels, and tidal backflow (Aderogba, 2012). Rapid population increase—estimated at over 20 million residents—has led to extensive land reclamation, informal settlements, and encroachment on wetlands. These changes disrupt natural water flows and greatly reduce the capacity of the urban environment to absorb floodwaters (Oduwaiye et al., 2019).

In recent years, several parts of Lagos such as Ikorodu, Lekki, Ajegunle, Victoria Island, Agege, and Lagos Mainland have experienced severe flood events that resulted in loss of lives, property destruction, traffic gridlock, business disruptions, pollution, and forced displacement of residents. The inadequacy of drainage infrastructure and the poor enforcement of physical planning regulations continue to worsen the situation (Ishaya & Ifatimehin, 2018). As flood events increase in magnitude and frequency, the need for reliable spatial assessment tools becomes more urgent.

Advances in Geographic Information Systems (GIS) and Remote Sensing (RS) now offer powerful analytical tools for assessing spatial patterns of flood vulnerability. GIS enables the integration and analysis of multiple environmental factors such as elevation, slope, land-use, hydrology, and population density, while Remote Sensing provides timely and accurate satellite-based observations of surface conditions (Jeb & Aggarwal, 2008). These technologies allow researchers and urban planners to produce vulnerability maps, identify high-risk zones, predict future flood scenarios, and strengthen disaster-risk preparedness.

Despite the increasing availability of spatial datasets in Nigeria, there remains a limited application of integrated GIS-RS-based flood vulnerability assessments in many flood-prone areas of Lagos. Existing studies often focus on general flood risk, without providing detailed vulnerability zoning based on multi-criteria spatial analysis. Therefore, an assessment using GIS and Remote Sensing tools is needed to generate reliable spatial information that can support policymakers, emergency managers, and community stakeholders in developing effective flood-mitigation strategies.

This study therefore seeks to assess urban flood vulnerability using GIS and Remote Sensing in selected flood-prone areas of Lagos State. The results are expected to provide a scientific basis for improving flood management, guiding infrastructure planning, and reducing the socio-economic impacts of flooding in Lagos.

1.2 Statement of the Problem

Urban flooding has become a recurring challenge in Lagos State, causing extensive destruction and disrupting the socio-economic life of residents. Despite ongoing efforts by government agencies, the impacts of flooding continue to worsen due to rapid urbanization, poor drainage maintenance, uncontrolled construction on floodplains, and limited early-warning systems. Many communities remain highly vulnerable because of inadequate spatial information about flood exposure, sensitivity, and adaptive capacity.

Most flood-risk management in Lagos still relies on reactive emergency responses rather than preventive, data-driven planning. In several flood-prone communities, accurate maps showing high-risk zones, drainage patterns, land-use changes, and elevation models are either outdated or unavailable. This makes it difficult for policymakers to make informed decisions on where to allocate resources, upgrade infrastructure, or implement relocation plans.

Additionally, Lagos has witnessed increasing rainfall variability and more frequent extreme weather events, further straining already overburdened drainage systems. Residents in densely populated informal settlements face particularly severe risks because their homes are built on low-lying reclaimed land, coastal wetlands, or alongside blocked canals. The socio-economic consequences—ranging from property loss to disease outbreaks and livelihood disruptions—underscore the urgent need for a systematic and spatially explicit vulnerability assessment.

GIS and Remote Sensing offer the ability to integrate multiple flood-inducing factors such as rainfall intensity, elevation, land-use change, slope, drainage density, soil type, and proximity to water bodies. However, these tools are underutilized in many parts of Lagos, and existing assessments do not sufficiently capture the multi-dimensional nature of flood vulnerability.

Given these gaps, there is a critical need to assess urban flood vulnerability using GIS and Remote Sensing to generate accurate spatial information for selected flood-prone areas of Lagos State. This study seeks to fill this knowledge gap by producing a comprehensive vulnerability map that can guide planners in reducing the recurrent impacts of flooding.

1.3 Objectives of the Study

The main objective of this study is to assess urban flood vulnerability using GIS and Remote Sensing in selected flood-prone areas of Lagos State.

The specific objectives are to:

1. Identify and map the major environmental and human-induced factors responsible for flooding in the study areas.

2. Analyze land-use/land-cover changes and their influence on flood vulnerability.

3. Use GIS and Remote Sensing techniques to develop a spatial flood vulnerability map.

4. Classify the selected areas into different vulnerability zones (low, moderate, high, and very high).

5. Provide recommendations for improving flood mitigation and land-use planning in Lagos State.

1.4 Research Questions

1. What are the major environmental and anthropogenic factors influencing flooding in the selected areas?

2. How have land-use and land-cover changes contributed to increased flood vulnerability?

3. What does the GIS-RS-based vulnerability map reveal about spatial variations in flood exposure?

4. Which areas fall within low, moderate, high, and very high vulnerability zones?

5. What mitigation strategies can reduce flood impacts in Lagos State?

1.5 Research Hypothesis

To guide the study, the following hypothesis was formulated:

H0: GIS and Remote Sensing analysis does not significantly identify spatial variations in flood vulnerability across selected flood-prone areas of Lagos State.
H1: GIS and Remote Sensing analysis significantly identifies spatial variations in flood vulnerability across selected flood-prone areas of Lagos State.

1.6 Significance of the Study

The study is significant because it:

• Provides scientific evidence to support flood-risk reduction policies.

• Helps government agencies identify high-risk locations for targeted interventions.

• Supplies spatial data for urban planners, environmental managers, and disaster-response teams.

• Enhances community awareness and preparedness for flood hazards.

• Contributes to academic literature on GIS-RS applications in hazard management in Nigeria.

1.7 Scope of the Study

The study focuses on selected flood-prone areas within Lagos State. It uses GIS and Remote Sensing datasets such as satellite imagery, digital elevation models (DEM), hydrological layers, and land-use maps. The analysis covers vulnerability assessment only; it does not implement mitigation infrastructure.

1.8 Operational Definition of Terms

• Flood: Overflow of water submerging normally dry land.

• Vulnerability: The degree to which people, infrastructure, or the environment are susceptible to harm from flooding.

• GIS: A computer-based system for capturing, analyzing, and displaying spatial data.

• Remote Sensing: Acquisition of information about the Earth’s surface using satellite or airborne sensors.

• Flood-Prone Area: A location that frequently experiences or is likely to experience flooding.

• Land-Use/Land-Cover: Human activities and physical features on the Earth’s surface.

Project – Assessment of Urban Flood Vulnerability Using GIS and Remote Sensing in Selected Flood-Prone Areas of Lagos State