THE EFFECT OF FLOOD ON ROADS DURABILITY IN NIGERIA
CHAPTER ONE
INTRODUCTION
- Background to the study
Disasters are said to have a devastating effect on economic development, livelihoods, agriculture, health, social, and human life around the world (Wood, 2005). They are unexpected events that can result in death or injury. Flooding is defined by Abam (2006) as a large volume of water arriving at and occupying the stream channel and flood plain in a time too short to prevent damage to economic activities, including homes. It is a natural hazard, similar to drought and desertification, that occurs as a result of an extreme hydrological (run off) event (Nwafor, 2006). It could also be defined as the inundation of an area that is not normally covered by water due to a temporary rise in the level of a stream, river, lake, or sea (Emodi, 2012). The most common causes of are prolonged rainfall events.
flooding worldwide. Floods are generally regarded as extreme hydrological events, where there is excess of water which may have devastating effects. Flooding in the tropics is considered partly or entirely climatological in nature, as it is caused by torrential rainfall, according to Ayoade (1988).
Flood disasters are not a new phenomenon in Nigeria, and their destructive potential can be enormous at times. Flooding is one of the major environmental crises ravaging the universe within the century and millennium, according to the United Nations Environment Program (UNEP, 2006). This is especially true in the majority of the world’s wetlands. The cause is attributed to the global rise in sea level caused by global warming, as well as the saturated nature of Nigeria’s wetlands.
Floods occur on many rivers on a regular basis, forming a surrounding region known as the flood plain. Human activities within cities, such as rapid industrialization and urbanization, population growth, natural resource exploitation, and infrastructure placement (dams, piers, and lands), exacerbate the occurrence of floods. According to Askew (1999), floods account for roughly one-third of all deaths, one-third of all injuries, and one-third of all natural disaster damages.
Floods in Nigeria can be classified into three types: coastal flooding, river flooding, and urban flooding. Coastal flooding occurs along the coast in the low lying mangrove and fresh water swamp belt (Folorunsho and Awosika 2001; Ologunorisa, 2004). It is usually caused by storm surge, waves (caused by wind), and heavy rainfall. River flooding
is determined by the amount of rainfall and runoff in the river valley. It happens in the flood plains of larger rivers, where sudden short-lived flash floods are associated with rivers in land areas, where sudden heavy rains can turn them into destructive torments in a short period of time (Folorunsho and Awosika 2001; Ologunorisa, 2004). Urban flooding, on the other hand, occurs in towns, particularly on flat or low-lying terrains where surface drainage has been neglected or where existing drainage has become clogged with municipal waste, refuse, and eroded soil sediments (Ali, 2005).
Oderrerho (2004) and Nwafor (2006) identified twelve (12) urban flooding causes. Surcharges in water level caused by natural or man-made flood construction
Paths, sudden dam failures, inappropriate land use, deforestation of catchment basins, reclamation, construction sites, and solid waste, insufficient drainage capacity to cope with urbanization, and excessive encroachment in flood ways are all examples of potential problems. The problem of urban flooding is a global one, but management practices vary depending on current technologies and adequacy in planning.
According to Nott (2006), flood events are not considered natural hazards unless they endanger human life and property. Low lying coasts and deltas, as well as small basins prone to flash floods, are the most flood-prone landscapes. Empirical studies (Okereke, 2007; Kolawole et al., 2011) have identified the primary consequences of flooding as loss of life, submergence of residences and streets, sewage inflow, municipal pollution, and property damage.
, traffic disruption, aesthetic discoloration, cleanup costs and service disruption, infrastructure damage, and economic loss.
Floods can disrupt people’s socioeconomic lives and livelihoods; in most cases, farmlands and livestock are submerged, which are the main sources of people’s income. Flood losses are devastating because many are never recovered after the flood. Floods cause significant damage to vulnerable communities, especially when the flood is unprecedented. Floods frequently cause hunger, famine, disease, and epidemic outbreaks (Mmom and Aifesehi, 2003). Malaria and typhoid outbreaks are common in tropical countries following floods. It is estimated that 300 million people in India and Bangladesh live in flood-prone areas (Nott, 2006).
It is It is well known that the water content of granular material increases the rate of road deterioration. Temperature gradients across the concrete slab can cause structural defects in rigid pavements (i.e., concrete). Diefenderfer and co. (2002). According to Diefenderfer et al. (2002), excess water has six negative effects: reduced shear strength of unbound materials, differential swelling on expansive subgrade soils, movement of unbound fines in flexible pavement base and sub base layers, pumping of fines and durability cracking in rigid pavements, frost-heave and thaw weakening, and stripping of asphalt in flexible pavements. On the plus side, ensuring proper (optimal) water content greatly improves road packing during construction and may also increase its resilience when trafficked, even though this is not proven.
The effect is frequently overlooked. Water and road construction do not get along, so it is generally preferred to keep the road as close to or less than optimum water content as possible over time. A.R. Dawson (2009).
Drainage is often described as the central and most important aspect of the design, construction, and maintenance of any road, including unsealed roads, according to McRobert, J. et al. (2000). Drainage of unsealed roads is especially important because lower quality design and construction standards and marginal materials, which are more permeable to water, are commonly used. If left unchecked, poor drainage will shorten the life of the pavement and have serious environmental consequences. There are numerous methods for reducing erosion of exposed surfaces.
Side drains, cut-off contour banks, and batter slopes are examples of unsealed road features. Any road will readily concentrate runoff, so roads must be designed and built to allow for frequent and safe discharge.
During rainstorms, some rainwater falls on the surface and some percolates through the soil mass as gravitational water until it reaches ground water. Some water is retained in the pores of the soil mass and on the surface of soil particles that cannot be drained by normal gravity, and this retained water is referred to as Held water. Surface water from the carriageway and shoulder must be effectively drained off without allowing it to percolate into the subgrade. The exterior Water from adjacent land should also be kept out of the roadway. The side drains should have enough capacity and longitudinal slopes to carry away all of the collected surface water. The failure of road pavements is caused by a variety of factors, including an increase in moisture content, a decrease in strength, mud pumping, the formation of waves and corrugations, stripping of bitumen, cutting of pavement edges, and frost action.
1.2 Statement of Problem
Flooding is not a new phenomenon for the people of Makurdi, who have lived in flood-prone areas for centuries. Makurdi, like most third-world cities, has experienced rapid population growth, which has resulted in changes in land use activities. Changes in land use, in particular, have a direct impact on flood magnitude and behavior (Civco et al 2002). Flash floods are common during the rainy season in Nigeria (May-October), but the country’s flood event in 2012 has been described as the most devastating in over 40 years.
Between September and October of 2012, two major events occurred in Nigeria: the Ladgo Dam flood in Adamawa State and the River Benue. Flooding in Niger and neighboring states (Niger and Benue States). Most of the country’s rivers were pushed over their banks, submerging hundreds of kilometers of urban and rural land. This resulted in a widespread devastating flood disaster that ravaged the country, destroying major cities in 14 states bordering the Niger-Benue River. Throughout the affected areas, the flood submerged houses and several transportation routes. An estimated 1.3 million people were displaced, 431 people were killed, and several hectares of farmland were destroyed (MISNA, 2012). Despite the fact that the unusually large flood was predicted by the Nigeria Metrological Agency NIMET, government at all levels failed to act on time, resulting in one of Nigeria’s worst humanitarian crises since the civil war in 1999. Despite the expected increase in the frequency and magnitude of floods in Nigeria, and invariably Makurdi, few impact assessment studies on people’s socioeconomic livelihoods have been conducted to determine the underlying causes of their vulnerability. In the absence of comprehensive data and information, flood-response measures have remained ad hoc.
- Objective of the study
The primary goal of this research is to investigate the impact of flooding on road durability in Nigeria. The study’s specific goals are as follows:
Determine the causes of flooding in Nigeria.
Investigate the socioeconomic impact of flooding in Nigeria.
Investigate the impact of poor drainage on flooding incidents in Nigeria.
To determine whether flooding affects road durability in Nigeria.
- Research Question
What are the reasons for flooding in Nigeria?
What are the socioeconomic effects of flooding in Nigeria?
Is a poor drainage system to blame for the floods in Nigeria?
Does flooding affect the durability of Nigerian roads?
- significance of the study
The significance of this research cannot be overstated because of its enormous importance to various groups of people who require the information that it will provide. It is significant for the following reasons:
The study will aid in flood management by providing an in-depth understanding and knowledge of the flood prevention strategies available, allowing them to effectively implement them.
The study will also serve as a source of secondary data for students and scholars planning similar research in the future.
- Scope/Limitation of the scope
The content of this study is limited to the flood effects on road durability, with a focus on Makurdi, the state capital of Benue state.