Application of Geoinformatics Techniques in Controlling Flooding in Vulnerable Roads and Buildings in Nigeria
Chapter One
Aim and Objectives
The aim of this research is to employ Geoinformatics (Geographical Information System (GIS), remote sensing and cartographic) techniques to generate flood vulnerability map showing buildings and roads that are susceptible to flooding in the study area of Port Harcourt at different buffer distances.
The following specific objectives were pursued in order to achieve the above aim:
- Conversion of existing analogue map to digital format by digitizing (creating spatial database).
- Creating a suitable attribute database for the study area.
- Link both spatial and attribute database.
- To generate buildings in the study area to ascertain those that are vulnerable to flooding.
- To produce vulnerability maps of the study area.
- To identify the impact which floods will have on the socio-economic livelihoods of the people.
- Make recommendations based on the findings.
CHAPTER TWO
LITERATURE REVIEW
Theory of Flooding
A flood is defined by the Oxford English Dictionary as an overflowing or irruption of a great body of water over land in a built-up area not usually submerged. Floods are natural phenomena, but they become a cause for serious Indirect flood damages are damages caused by disruption of physical and economic linkage of economy and the extra costs of emergency and other actions taken to prevent flood damage and other losses. But damages which can be specified in monetary terms such as loss of production are called tangible damages and those that cannot be valued in monetary terms such as casualties, health effects and damages to ecological goods which are not traded in the market are for more difficult to assess in monetary terms.
Quantification of flood damages is quite difficult as it has other developed issues year after. But flooding and its damages in global, national and district perspectives are discussed below.
Flooding in Global Perspective
According to Cunningham and Cunningham (2011) flood occur when it’s flow of a stream becomes so great that it exceeds the capacity of its channel and overflows it’s banks. They further concern when they exceed the coping capacities of affected communities, damaging lives and property. Globally floods are the most frequently occurring destructive natural event affecting both rural and urban settlements (Jha et al., 2012).
Understanding Flood Damages
Flood damages refer to all varieties of harm caused by flooding. It encompasses a wide range of harmful effects on humans, their health and their belongings on public infrastructure, cultural heritage, ecological system, industrial production and the competitive strength of the affected economy. Flood damages differ occasionally but are mostly categorized firstly into direct and indirect damages and secondly, Tangible and intangible damages (Parker et al., 1987; Pennizing Rowsell et al., 2003; Messner and Meyer , 2005).
The research works of (Parker et al., 1987; Penning Rowsell et al., 2003; Messuler and Meyer, 2005) explain that direct flood damage covers all varieties of harms which relate to the immediate physical contact of flood water to humans property, and the environment. This includes for example damage to buildings, economic assets, loss of standing crops and livestock in agriculture, loss of human life, immediate health impacts and loss of ecological goods. indicated situation where torrential rains in June 2008 caused massive flooding across the American Midwest, where many cities in Lowa, Wisconsin, Illinois and Indiana experienced their highest water levels in more than a century. In Cadar Rapids, Lowa, for example, almost the entire downtown was inundated by the over flowing Cadar River,
Flooding in Nigeria
Floods are an extreme naturally occurring weather event that result in an overflowing of large amount of surface water over land that is not always inundated (Adeoye et al., 2009). It is considered to be the worst natural disaster in the world and it is responsible for a third of all natural problems and half of damage on facilities around the globe. It has become one of the most frequent natural occurrences in the last few decades (Jeb and Aggarwal, 2008).
Floods have cost damages to societies totalling more than 250 billion dollars and the intensity and frequency of floods are increasing globally. It is gradually becoming a common phenomena around the world, caused by increase in global temperature that result in torrential rains and rise in sea level that over flowed their banks and flood surrounding coastal lands (Jeb and Agigarwal, 2008).
In Nigeria, aside from droughts, floods cause almost 90 percent of damages resulting from natural hazards (Adeoye et al., 2009). Floods that occur in Nigeria are as a result of extensive rainfall, drainage blockage and dam failure (Jeb and Aggrawal, 2008). The effect of floods in Nigeria has been on the increase especially in the last three decades. It has become a life threatening concern to the citizenry and the number of deaths and damages caused by this perennial disaster are alarming.
The Federal Government of Nigeria in its own part has invested millions of dollars both on the relief and compensation as well as rehabilitation of flooded area yet the menace is still unabated (Jeb and Aggarwal, 2008). These days, flooding is fast becoming a serious environmental problem resulting in huge loss of lives, property price less arable land. Floods have rendered many people homeless and disrupted a lot of socio – economic activities in both urban and at rural areas. Various flood plains and land along the Atlantic Ocean coast, raves or lake are affected by flooding yearly in Nigeria (Jeb and Aggarwal, 2008).
CHAPTER THREE
METHODOLOGY
It involves the overall methods, approaches and materials adopted. It mainly explains the data sources and types, methods of field data collection, reference data used, identification, image classification technique, weighted Analysis employed, accuracy assessment, statistical analyses and list of software packages used to achieve the research objective.
Data Requirement
Data required in this research includes:
- Landsat 8 OLI imagery covering the study area
- Shuttle radar topographic mission (SRTM) covering the study area.
- Shape file of the administrative boundary of Rivers State
Data Acquisition
Acquisition of Primary Datasets
These data were obtained through field visits peculiar to the research at hand. They include
- The coordinates of sample points of land cover/ landuse to be used for accuracy assessment was obtained using handheld GPS.
- Non-spatial (attribute) data describing the characteristics of Land cover/ land use identified on the scene was collected.
Acquisition of Secondary Datasets
The secondary datasets needed was obtained from already existing medium. They include:
- Shape file of the administrative Rivers State, which was obtained from the Department of Surveying & Geoinformatics, Nnamdi Azikiwe University Awka.
CHAPTER FOUR
RESULTS PRESENTATION AND DISCUSSION
In this section, results of image analysis as obtained from the classification procedure of supervised classification and flood mapping are presented. Most of the discussions are supported by maps, tables and illustrative graphs.
Land cover / Land use Mapping
Land cover / Land use Distribution of Rivers State 2019
In mapping land cover/land use, four different classes were identified to include Built up areas, vegetation, open space, farmland, mangrove and water bodies. The classified image of Rivers State is shown in figure 4.1
CHAPTER FIVE
CONCLUSION AND RECOMMENDATION
Conclusion
This study aimed at investigating flood vulnerability in parts of Rivers State using flood Remote Sensing and GIS. Its objectives were to delineate different vulnerability levels of flooding in the study area, to determine the effect or impact of flooding on different land cover types and to produce flood vulnerability map of the study area. The methodology involves data acquisition, data processing and reclassification and overlay analysis. This study has been able display the usefulness of Remote Sensing and GIS technologies in classifying and in identifying areas with high, moderate, low vulnerability of flooding within the study area.
The classification achieved an overall Classification Accuracy of 85.99% and kappa statistics of 0.8992. The image classification results indicate that vegetation accounted for the largest land cover/use of about 37.23 % with an area of 4096 km2 while built up area had the second largest with 31.48 % and an area of 3463 km2, water body had 11.51 % with an area of 1267 km2, open space had 9.78 % with an area of 1076 km2 and mangrove had 9.98 % with an area of 1098 km2. The flood vulnerability mapping results also indicated that high- vulnerability zone occupied 28.60% of the entire study area, covering an area of 3147km2, while moderate vulnerability zone occupied 27.28%, covered an area of 3001km2. Low vulnerability zone occupied 27.05% covering 2976km2 while no vulnerability zone occupied 17.05% covering an area of 1876km2.
Recommendations
Based on the results and analysis obtained, the following recommendations were made:
- the vulnerability maps produced in this research are beneficial and are recommended that they be used in encouraging vulnerability zone residents to prepare for the occurrence of flooding.
- It is recommended that the results achieved in this research can be used as a base to help identify areas at vulnerability of being flooded in the study area.
REFERENCE
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