Causes Of Gully Erosion In Nigeria And Possible Solutions

Project and Seminar Material for Civil and Environmental Engineering

Causes Of Gully Erosion In Nigeria And Possible Solutions


Abstract


Gully erosion, the most impressive and striking erosion type, has been recognized as one of the major global environmental problems. This study therefore sought to address the causes of gully erosion in Nigeria and possible solutions. Many States in Nigeria are currently under the threats of this phenomenal process, south-eastern part of the country being the most affected. It has numerous causes; and these causes can be both naturally and artificially-induced, but the underlying geology and the severity of accompany surface processes play a key role. Observations have shown clearly that gully erosion is more prevalent in sedimentary terrain than in the basement complex of Nigeria. This erosion activity at various scales has resulted in the loss of lives and properties almost on a yearly basis. Solutions that have been proffered include public awareness campaign, improved farming techniques, cultural method of gully control, enactment of laws against any activities that favour gully growth, and thorough implementation of suggested solutions.

 


Table of Content


Chapter One

1.0 Introduction

  • 1.1 Background of the Study
  • 1.2 Statement of Problem
  • 1.3 Objective of the Study
  • 1.4 Research Questions
  • 1.5 Hypothesis
  • 1.6 Significance of the Study
  • 1.7 Scope of Study
  • 1.8 Limitation of the Study
  • 1.9 Definition of Terms
  • 1.10 Organization of the Study

Chapter Two

2.0 Review of Related Literature

  • 2.1 Conceptual Review
  • 2.2 Factors of Gully Erosion Formation
  • 2.3 Types of Gully Erosion
  • 2.4 The Impacts of Gully Erosion
  • 2.5 Gully Erosion Processes
  • 2.6 How Gullies Develop
  • 2.6.1 A Four Meter Deep Gully Advancing into Grazing Land
  • 2.6.2 Dispersible Sub-Soils
  • 2.6.3 Tunneling
  • 2.6.4 Cracking Clay Soils
  • 2.6.5 Saline Areas
  • 2.6.6 Triggers for Gully Development
  • 2.7 Socio-Economic Effects of Gully Erosion: A Global Perspective
  • 2.8 Theoretical Framework
  • 2.8.1 The Davison Theory

Chapter Three

3.0 Methodology

  • 3.1 Research Design
  • 3.2 Data Collection
  • 3.3 Data Analysis

Chapter Four

4.0 Results and Discussion

  • 4.1 Causes of Erosion
  • 4.2 Impacts of Gully Erosion
  • 4.3 Proposed Solutions to Gully Erosion in Nigeria

Chapter Five

5.0 Summary, Conclusion and Recommendation

  • 5.1 Summary
  • 5.2 Conclusion
  • 5.3 Recommendation
  • References

Chapter One


1.0 Introduction

1.1 Background of the Study

Soil erosion is widely recognized as a major environmental and agricultural problem affecting many parts of the world. Estimates suggest that, each year, as much as 75 billion ton of soil are removed from the land by wind and soil erosion, with most of it coming from agricultural land (Pimentel et al., 1995). While the rates at which soil erosion occurs vary over time between different locations, it has intensified in recent years, causing great concern in developing countries. The “on- site” impacts of soil erosion are commonly associated with shortages of arable land that is capable of supporting agricultural production, common in Asia and Africa, but also in Europe. While 0.5/ha of arable land per capita is deemed necessary to ensure people are given a diverse diet, Pimentel et al. (1995) in (Mbaya 2013) estimates that about one-half of this is currently available. The short and medium term consequences for developing countries are evidenced by the widespread prevalence of food shortages and malnutrition. Within the next forty years, he further predicts that the effects of soil erosion and rapid population’s growth could mean that a little over a quarter of the arable land per capita deemed necessary to ensure people diverse diets, will be available.
There are also downstream or “off-site” impacts of soil erosion. For instance, eroded sediments can be deposited in reservoirs, reducing hydro-electric generation and the flow of water supplies for irrigation and residential uses (Mbaya 2013). The use of large amounts of fertilizers, pesticides and irrigation to help off-set the deleterious effects of soil erosion have the potential to create pollution and health problems, as well as destroying natural habitats and this contribute to high energy consumption and unsustainable agricultural systems (Pimentel et al., 1995) in (Mbaya. 2013).

The World Bank (1990) in (Mbaya, 2013) recognized three main environmental problems facing Nigeria: soil degradationand loss, water contamination and deforestation. Gullyerosion contributes to each of the three main problems and causes damage with an annual cost to the nation, estimated at $100 million in1990.Unfortunately, the situation has not changed significantly in recent years. As at 1997, there were 5,700 gully erosion sites nationwide (Agagu, 2009) in (Mbaya 2013). This figure has certainly increased. For example in 2009, the World Bank Country report on Nigeria still listed gully erosion as one the top five major hazards threatening the Nigerian environment. Numerous new gullies have emerged and many of old gullies have grown rapidly to disaster levels. Accelerated erosion with its effects on agriculture in Nigeria is well documented, but the fact that several Nigerian towns facing gully erosion is far less well known. Urban gully erosion affects only 18,517km2, representing only 2% of the total area of Nigeria (Titilola et al., 2008) and so tends to be ignored in the literature. However, the area of land affected by gullies is not the sole criterion for estimating the damage they inflict on the national economy. The value of the lands they destroy and the cost of protective measures should be considered.

Gully erosion in towns, destroys valuable land, communications facilities, lives and buildings. This involves expensive control measures and requires more research work. The expansion of concreted surfaces in towns, heightened volume and velocity of runoff that is generated have tended to make many Nigerian towns increasingly susceptible to gully formation. When most of the available land in an urban area is built-up, increased pressure on land might lead to extension of urban land use to the stream channels, flood plains and restriction of streams to artificial channels.This is the situation being experienced in most towns and rural areas in Nigeria. Gully erosion is a major problem in Nigeriatown since 1980s. The infrastructural development coupled with demographic increase, have no doubt heightened the problems of gully erosion in the country.

Residents of towns and rural areas have expressed concern over accelerated erosion rates. These concerns addresses not only the loss of personal property, but also that gully erosion is causing functional and structural damage to infrastructures such as culvert outlets and roads within the stream channels as well as other public and private structures along the channel. The Federal and State Governments have attempted to solve the problem through numerous contracts awarded for gully erosion project at some key sites in Nigeria. However, the economic practicalities and engineering control measures has not met people’s expectation, owing to lack of adequate information on the gully morphological parameters. Therefore, solving the gully erosion problem in Nigeria requires concerted research efforts.


1.2 Statement of Problem

Gully Erosion is caused by unwise human activities such as deforestation, over- grazing, and unplanned construction activities. Gully erosion problems whether they are huge or small can definitely be controlled and prevented. Gully erosion control measures are usually grouped into two categories: agronomic and engineering. Agronomical control method provides the soil with physical protection against scour and in slowing down the velocity of flow by increasing the hydraulic resistance of the channel (Lal,1988). Controlling of erosion means reducing the rate of eroded soil to it barest minimal. According to Abubakar (1996), before any actions are taken to correct soil erosion, there is need for proper understanding of the causes. Without understanding the causes of soil erosion, any control measures taken may be waste of time and money which may even worsen the problem. Lal (1988) observed that experts from the field of Conservation, Geomorphology, Soil Geography, Forestry and Agriculture have recommended some control measures in various parts of the world. These control measures have been successful in some areas and unsuccessful in other areas. The need for sustainable soil erosion control depends on the study and understanding of several conservation strategies. Soil erosion is a serious problem in Africa due to several factors responsible.

Soil erosion as a problem in Africa has been attributed to numerous causes such as tropical deforestation, overgrazing, agricultural intensification, urbanization and low soil fertility (Lal, 1988). With the continue consequences of soil erosion problems, assessing merits and limitations of different control measures is a topical issues that are of great concern because of the ever-shrinking prime land resources and deteriorating environmental quality. This global concern for soil erosion problem is because soil as a resource is non-renewable in the human time scale. From an ecological and economic standpoint, soil erosion is probably the most serious environmental problem facing land resources in Nigeria. Dudley (2000) suggests that the dangers have become progressively more serious as there are undue pressures on land by agriculturist. This is as a result of increase in both human and animal population with consequent urbanization, deforestation and over exploitation of land resources. Studies of soil erosion in the country have been undertaken by different researchers. According to Areola (1999) much has been said and written about soil erosion in different parts of Nigeria. Blaikie (1991) observed that there are areas where the causes and impact are the major concern but there is need to look at the effectiveness of the control measures that are put in place.

The control and prevention of soil erosion rely upon the selection of appropriate control measures and conservation strategies. Gully erosion as a form of soil erosion is an environmental disaster currently plaguing lands that would have otherwise been used for infrastructural developments. Eseigbe, and Ojeifo (2012) observed that the handling, controlling and monitoring of soils in Benin City must be geared towards achieving quality environment for man.

This is because soil erosion in the area is caused by a multidimensional factor. One of the main causes of gully erosion in is road construction with inappropriately terminated drainage network. This is because gullies that develop due to this poor road construction are allowed to get to a worst state before solutions are sorted for by individuals, corporate organizations and government. This study therefore seeks to address the causes of gully erosion in Nigeria and possible solutions.


1.3 Objective of the Study

The main aim of this study was to address the causes of gully erosion in Nigeria and possible solutions. The specific objectives are outlined as follows;

  1. To determine the causes of erosion in Nigeria
  2. To determine the impacts of gully erosion in Nigeria
  3. To identify solutions and control measures of gully erosion in Nigeria

1.4 Research Questions

In other to achieve the objective of the research, the following research questions were formulated:

  1. What are the causes of erosion in Nigeria?
  2. What is the impact of gully erosion in Nigeria?
  3. What are the solutions and control measures of gully erosion in Nigeria?

1.5 Hypothesis

  • HO1: There is no significant impact of gully erosion in Nigeria
  • HA1: There is a significant effect of gully erosion in Nigeria

1.6 Significance of the Study

Information derived from the evaluation of the degree of environmental degradation caused by gully erosion in Nigeria will facilitate the assessment of the possible effects gully erosion would have on the environment. It will enlighten the public on the inherent dangers associated with areas that are prone to gully erosion. It will also help in classifying the land in terms of degradation.

The study will help to create awareness on the need for a considerable improvement on the gully erosion development and management practices, and equally offer some significance to academic community in understanding the operational mechanism of gully erosion.

The affected areas are part of the economic hub of the country, and this study will also provide a reference point for future researchers in the country.


1.7 Scope of Study

The study is limited to towns and rural areas in Nigeria. The study is restricted to address the causes of gully erosion in Nigeria and possible solutions.


1.8 Limitation of the Study

The limitation of the study includes: Some baselines data and maps that ought to have been provided by the government were not available and even the government officials were not free enough to release information because the believed that the research was politically motivated even when there was an evidence to show that it was purely an academic exercise.

Accessibility into the gully areas was a big limitation due to shortage of personnel to help in undertaking the measurements of the width and length of the gully. The unwillingness of some of the respondents to give information required about the gully and unavailability of the required instruments for the measurements of the gullies are some of the obstacles surmounted while carrying out the study.


1.9 Definition of Terms

Causes:

Is the reason or origination of something, in this case the origin if gully erosion in Nigeria.

Gully Erosion:

Gully erosion is the removal of soil along drainage lines by surface water runoff. Unless steps are taken to stabilise the disturbance, gullies will continue to move by headward erosion or by slumping of the side walls. Large gullies that have been left unchecked are difficult and costly to repair.

Solutions:

A means of solving a problem or dealing with a difficult situation, in this study, means of solving gully erosion.


1.10 Organization of the Study

This study is divided into five chapters. The first chapter is the introduction which contains the background, research problems and objectives. The second chapter is the literature review and the third chapter is the methodology. In the fourth chapter, the researcher analyses the data and discusses the results. The fifth chapter is the last chapter which presents the summary, conclusion and recommendations.


Chapter Five


5.0 Summary, Conclusion and Recommendation

5.1 Summary

The study was carried out to address the causes of gully erosion in Nigeria and possible solutions. Gully erosion has been on increase and advancing at alarming rates over the past few decades in Nigeria, causing untold hardships, misery, loss of houses, lives and other properties worth millions of naira. As human population within the study area rises, more land is cleared of its available natural vegetation and replaced with impervious surfaces leading to low infiltration-runoff ratio. The situation is further worsened by rise in value of urban land due to population increase. These force people to erect buildings on floodplains, consequently increasing the magnitude and frequency of gully erosion in response to high storm water runoff and channel concentration, this led to more destruction of lives and properties as observed in the study area. There exist no significant structures of protection instituted by government for victims of the menace. The affected population is almost left to cope with and manage the disaster on their own.

Solving the problem of gully erosion in Nigeria therefore; requires adequate funding, committed political will (not lip-service) and well-articulated sustainable policies. The development of an effective gully erosion control/prevention management programme must be based on accurate scientific and engineering data on the size of the gullies, the engineering geological properties of the soils, the characteristics (volume/velocity) of the surface run-off and the associated human activities. The implementation of the adopted remedial management programme, must be holistic in approach, (preferably on watershed basis), with well-coordinated participation of government, private sector and the affected communities.


5.2 Conclusion

Nigeria and elsewhere in the world suffer from the havocs of gully erosion. The causes of gully erosion in Nigeria include both natural and anthropogenic sources. The impacts include loss of human and animal lives, loss of properties and land resources. Some of the solutions that are proffered include improved farming techniques, cultural method of gully control, and enactment of laws against any activities that favour gully growth. The government at all levels in Nigeria and the stakeholders in environmental management such as State Ministry of Environment and Federal Ministry of Environment should also sensitize Nigerians on the causes, impacts and problems of gully erosion. However, poor or lack of implementation of research findings and recommendations seem to hinder complete evaluation of proposed solutions. For instance, in some cases where an effort is made, poor quality of work usually lead to even greater erosion, as in the case of road construction probably due to poor supervision, poor funding and corruption.


5.3 Recommendation

Though we have little or no control on the natural causes of gully erosion especially those related to the underlying geology, the individuals and relevant stakeholders should discourage all practices that are capable of initiating or speeding the phenomenon in Nigeria. If all the suggested solutions are carefully looked into, it is believed that the incidence of gully erosion in Nigeria would be drastically reduced and the security of the lives of Nigerians and their properties will be guaranteed.

Furthermore, a scientific and systematic approach which integrates the influence of all factors responsible for gully development and growth should be adopted for the control of gullies within the state and region. These control measures should be extensively applied and monitored for effectiveness


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