1.1 Introduction
Flood is defined as the overflow of water onto normally dry land, usually caused by heavy rainfall, river overflow, storm surges, or inadequate drainage systems, resulting in temporary submergence of land areas and disruption of human activities (IPCC, 2021). Flooding is one of the most common and destructive natural hazards globally, with increasing frequency and intensity attributed to climate variability, land use change, and rapid urbanization (UNDRR, 2022).
In Nigeria, flood disasters have become a recurring environmental challenge affecting both urban and rural communities. The impacts are particularly severe in floodplain regions where settlements are located close to major river systems. Lokoja in Kogi State is situated at the confluence of River Niger and River Benue, making it one of the most flood-prone areas in the country. Seasonal rainfall and upstream water discharge from dams and tributaries frequently lead to inundation of large portions of the floodplain, resulting in loss of lives, displacement of people, destruction of infrastructure, and economic setbacks (NEMA, 2021).
This chapter will address the background information that motivated this study, the challenges that prompted it, its aim, and its objectives as a preface to subsequent sections of the study. Additional factors include the study's significance, scope, limitations, research questions and hypotheses, and the definition of technical terms.
1.2 Background of Study
Flooding is widely recognized as one of the most devastating natural hazards affecting human settlements, infrastructure, and ecosystems across the globe. According to the Intergovernmental Panel on Climate Change (IPCC, 2021), flood events are increasing in frequency and intensity due to climate change, rising sea levels, and extreme precipitation patterns. Flooding occurs when water overflows onto normally dry land as a result of heavy rainfall, river overflow, dam failure, or inadequate drainage systems, leading to widespread environmental and socio economic disruptions. In many developing countries, the impacts of flooding are worsened by rapid urbanization, poor spatial planning, and inadequate disaster preparedness systems (UNDRR, 2022).
According to the United Nations Office for Disaster Risk Reduction (UNDRR, 2022), flood disasters account for a significant proportion of global disaster-related losses, especially in low income regions where vulnerability is high and mitigation capacity is low. The organization reported that increasing human settlement in floodplain areas significantly amplifies exposure to flood hazards, thereby increasing mortality rates and economic losses. Similarly, the National Emergency Management Agency (NEMA, 2021) stated that Nigeria experiences seasonal flooding almost every year, with varying degrees of severity affecting several states, particularly those located along major river basins.
Aderogba (2013) asserted that, urban flooding in Nigeria is largely driven by uncontrolled development, blocked drainage channels, and the encroachment of natural waterways. The author asserted that many urban settlements expand into flood-prone zones without adequate environmental assessment, thereby increasing their vulnerability to flood disasters.
Lokoja, the capital of Kogi State, occupies a unique geographical position at the confluence of River Niger and River Benue. This location makes it one of the most flood-prone areas in Nigeria. According to NEMA (2021), Lokoja has experienced severe flood events in recent years that have led to displacement of residents, destruction of homes, and disruption of transportation networks and economic activities. The agency reported that the 2012 and 2022 flood incidents were among the most devastating, affecting thousands of households and causing extensive infrastructural damage.
Olorunfemi and Adeyemi (2015) articulated that, floodplain environments are naturally susceptible to periodic inundation due to their low elevation and proximity to major water bodies. The authors asserted that sustainable flood management in such regions requires accurate mapping and continuous monitoring of flood-prone zones. They further contended that without proper delineation of flood risk areas, disaster response and mitigation strategies become less effective and reactive rather than proactive.
Remote sensing technology has emerged as a powerful tool for environmental monitoring and hazard mapping. According to Jensen (2016), remote sensing involves the acquisition of information about the Earth's surface without direct contact, using satellite or aerial sensor systems. The author stated that remote sensing provides spatial and temporal data that are essential for detecting land use changes, monitoring flood extent, and assessing environmental risks. Similarly, geophysical methods such as electrical resistivity and seismic surveys provide subsurface information that helps in understanding soil properties, groundwater movement, and infiltration characteristics that influence flooding behavior.
Sharma and Singh (2018) affirmed that, the integration of remote sensing and geophysical techniques enhances the accuracy of flood risk assessment by combining surface and subsurface datasets. The authors affirmed that remote sensing alone may not provide sufficient information on underlying soil conditions, while geophysical methods complement this limitation by revealing subsurface structures that influence water accumulation and drainage patterns. In Lokoja floodplain, the increasing pressure from population growth and urban expansion has significantly altered the natural landscape. According to Okoli and Eze (2020), unregulated construction activities and deforestation have reduced the land's natural absorption capacity, leading to increased surface runoff during heavy rainfall events. The authors reported that these human induced factors have intensified the severity and frequency of flood occurrences in the area. They further stated that poor drainage infrastructure and inadequate enforcement of environmental regulations continue to exacerbate flood risks.
This study is set against the backdrop of increasing flood vulnerability in Lokoja floodplain, rapid urban expansion, environmental degradation, and the need for improved flood risk mapping using advanced geospatial and geophysical techniques.
1.3 Statement of Problems
Investigation revealed that flood disasters have become recurrent, particularly in riverine and floodplain communities where population pressure and unregulated land use intensify exposure to risk (NEMA, 2021). Lokoja floodplain in Kogi State is a major confluence zone of River Niger and River Benue, making it highly vulnerable to seasonal flooding that often results in displacement of residents, destruction of property, and disruption of socio economic activities.
Additionally, remote sensing data provides spatial and temporal information on land use changes and flood extents, while geophysical techniques support subsurface characterization that improves understanding of groundwater flow and soil saturation patterns influencing flood occurrence (Aderogba, 2013). However, these tools are not sufficiently integrated into flood risk studies in the area, leading to gaps in reliable hazard mapping and planning.
Furthermore, rapid urban expansion within Lokoja floodplain has intensified surface runoff due to increased impervious surfaces and reduced natural drainage capacity. This situation worsens flood intensity during peak rainfall periods. On the other hand, insufficient enforcement of environmental regulations and poor urban planning contribute significantly to the continued occupation of high risk flood zones, thereby increasing vulnerability among residents. It is against this backdrop that this study seeks to delineate flood prone areas using remote sensing and geophysical methods in the Lokoja floodplain of Kogi State.
1.4 Aim and Objectives of Study
The aim of this study is to delineate flood prone areas using remote sensing and geophysical techniques in Lokoja floodplain, Kogi State.
The specific objectives of the study are to:
- Identify land use and land cover changes influencing flood occurrence in Lokoja floodplain
- Analyze topographical and hydrological characteristics of the study area
- Determine subsurface soil and groundwater conditions using geophysical methods
- Map and delineate flood prone zones using remote sensing data and GIS techniques
- Evaluate the relationship between surface conditions and flood vulnerability in the study area
1.5 Research Questions
The study came up with research questions so as to be able to ascertain the above stated objectives. The specific research questions for the study are stated below as follows:
- What land use and land cover changes contribute to flood occurrence in Lokoja floodplain?
- What are the topographical and hydrological characteristics influencing flooding in the study area?
- What subsurface soil and groundwater conditions affect flood behavior in Lokoja floodplain?
- How can remote sensing and GIS be used to map flood prone zones in the study area?
- What is the relationship between surface conditions and flood vulnerability in Lokoja floodplain?
1.6 Significance of Study
It is believed that at the completion of the study, the findings will provide accurate flood prone maps that will support disaster preparedness and planning in Lokoja floodplain. The study will also assist government agencies in developing improved flood mitigation strategies that will reduce loss of lives and property in Kogi State.
Furthermore, the study will support urban planners in regulating settlement expansion into high risk flood zones in the area under study. In addition, this research will provide geospatial and geophysical data that will enhance flood monitoring and early warning systems in Nigeria.
Lastly, the study will contribute to academic knowledge on the integration of remote sensing and geophysics in flood risk assessment.
1.7 Scope and Limitations of the Study
The study is focused on Lokoja floodplain under the administrative jurisdiction of Kogi State Government and utilizes satellite imagery and geophysical survey data to assess flood vulnerability patterns.
1.8 Definition of Terms
Flood:
Flood is the overflow of water onto normally dry land caused by excessive rainfall, river overflow, or drainage failure, leading to temporary inundation of land areas (IPCC, 2021).
Delineation:
Delineation refers to the process of identifying and mapping boundaries of specific geographic or environmental features such as flood prone zones using scientific tools (Jensen, 2016).
Remote Sensing:
Remote sensing is the acquisition of information about the Earth's surface without physical contact using satellite or aerial sensor systems (Jensen, 2016).
Geophysics:
Geophysics is the study of the Earth's physical properties using methods such as electrical resistivity and seismic surveys to analyze subsurface conditions (Sharma & Singh, 2018).
…