CHAPTER ONE
1.0 INTRODUCTION
1.1 BACKGROUND OF THE STUDY
Soil erosion is a naturally occurring process whether it is by water, wind or ice, involves the actions of soil detachment, movement and deposition. It could be a slow process that continues relatively unnoticed or can occur at an alarming rate, causing serious loss of top soil (Jim, 2012). Loose soil, low organic matter, loss of soil structure, poor internal drainage, salination and soil acidity problems are other serious soil degradation conditions can accelerate the soil erosion process.
Erosion is a natural process that is prompted by man-made human (anthropogenic) activities such as deforestation that involves the removal of vegetation, overgrazing, unmanaged construction of building and roads. Excessive erosion can produce ecosystem damage, loss of soil and receiving water sedimentation. The effect of soil erosion is sometimes linked to over population (Cohen, 2007). He further stated that erosion tends to remove topsoil at a faster rate than soil is accumulated in an area. This results in collapse of buildings, especially those of poor foundation. This affects settlement development by residents within the study area. However, increased soil erosion at a much faster rate than soil is accumulated materially or artificially is a recent problem due to mankind’s conservation which in action makes the land unprotected and vulnerable to degradation. Other natural causes are occurring adduced the rainfall with wind storms to make wreck havoc on the environment. This ugly effects occurs both in residential and agricultural/farming areas as well as the natural environment. The effects of soil erosion are found insitu (on-site) where the soil become detached), as well as off-site where the eroded soil is transported. Also, in form of the high rainfall, storms obviously cause deep gullies, but erosion due to smaller events can seem in form of sheets with no consequence, but in fact there is a cumulative effect on a long-term basis.
Cohen (2007) stated that, the most serious consequence of soil erosion globally is the treat to long-term sustainability of agricultural productivity and hindrance to settlement development. This eventually leads to development of rugged terrain and collapse of buildings. The destructive impact of erosion is felt on developing countries such as Africa and Asia, and developed countries for which there is a huge environmental concern.
Soil erosion results in the loss of soil fertility that makes the land barren that accumulate more than 25 million hectares of barren lands in the world and to desertification (Tutor Vista, 2013). High rainfall of short duration and torrential downpour results in flash floods that make rivers overflow their banks, destroy foundation and collapse buildings, washed away live stock and act as hindrance to settlement development (Adelye and Rustum, 2011). Also, it could damage bridges and causes a dam to overflow to submerging buildings, displace people from homes, with attendant loss of personal valuables and ongoing psychological fear and insecurity caused by such event (Bariweni, Tawari and Abowei, 2012). Like wind and water, coaster erosion is a natural process but can be exacerbated by human activities. Activities that can influence Agbor erosion of river droughts, include, mining of sand for construction purposes, building on the beach, to interfere natural movement of sand and impedes beach recovery, removal of vegetation from sand dunes, to destabilize protective barriers, from waves and currents. Erosion not only cause damages to the immediate area where it occurs but also have negative effects on the surrounding environment. Water erosion often destroys buildings, roads and fences and other type of structures, including bridges, cars, buildings, sewage systems, roadways and canals, etc.
The economy can also be severely affected by flooding. Businesses may lose stock, patronage, data and productivity and cause disruption to utilities and transport infrastructure with knock-on effects to a wider area. Tourism, farming and livestock’s can equally be affected. The built environment may be damaged or destroyed as a result of erosion and flooding with high repair costs and long periods required for reinstatement. The public realm is often badly affected through damage and deposit of potentially large quantities river accumulated of debris. Land contamination may occur and spread during erosion. Individual properties and vital infrastructure may also be damaged or disrupted, communication, electricity and gas supplies can be interrupted, to wider communities if sub stations and transport are eroded. Road links, railways, canals, etc, may be blocked causing disruption to the wider transport network and accessibility and also result in severely disrupted local inhabitants settings, especially amongst those considered most vulnerable (Bariweni, Tawari and Abowei, 2012). This phenomenon is a common site in Agbor and its environs, posing direct threat to settlement development in the area and the destructions of building infrastructures in its surrounding rural areas. Cohen (2007) said that improved land use techniques such as terracing, of building and tree planting can limit erosion. It is against this background that this study is carried out to find lasting solution to curb the problems caused by soil erosion especially as it affects settlement in the study area.
1.2 STATEMENT OF PROBLEM
Environmental hazards including erosion gave rise to lopsided concentration of vehicles in some of the roads thus making the roads, a place of great conflict between man and the environment.
It has also been observed that improper planning in Agbor has resulted to in erosion, streets flooding, because in most areas, it was observed that settlements, buildings and other structures were built across River Plains and along flood water path as well as erosion sites and flood plains, thus obstructing the free flow of run-off result causing erosion.
Soil erosion has posed a serious threat to Agbor and its environs, facing the problems resulting from erosion. During the wet or raised season, some areas are become inundated to uninhabitable and unmotorable. Local Government and individual in affected areas, have tried to control erosion problem without professional input by filling up the affected areas with gravel, building embankment, placing sand bags and planting trees.
Erosion is now synonymous with disaster, dangers, despair, destruction, death and damage to economic properties. Environmental problems caused by urbanization, removal of the natural cover exposes the soil to the action of running water. This greatly reduces the fertility of the soil to cause development of monstrous soil gullies in the land.
Though, there is no statistics data on the extent of soil erosion and fertility in degraded areas of Agbor, there is enough evidence to show that, the topsoil is increasingly depleted by soil erosion though outdated and unscientific practices. The impact of unchecked settlement development as a result of rapid urbanization has further aggravated the problem.
Some of the natural factors which tends to increase soil erosion in Agbor include: soil type, soil slope and topography. The inherent low statues of soil has much impact on the effects of organic matter on soil properties. Soil is also lost when it is down slope, road network, commercial places, building which result from urbanization and other life and properties.
It has been observed that the dual factors of topography and heavy rainfall affect the entire land area of Agbor. That is, most part of the region has been plagued and subjected to erosion which has resulted to menace to her inhabitants. A lot of studies have been carried out by scholars on the causes of erosion and this research will therefore focus on the effects and solution to soil erosion on settlement in Agbor and its environs.
1.3 RESEARCH AIMS AND OBJECTIVE
The major purpose of this study is to determine. The effective way of controlling erosion in a construction site prone to erosion problem.
1) Identity the various causes of erosion in settlements.
2) Examine the appropriate materials and (new and old) used in controlling the erosion.
3) Determine the most appropriate materials and techniques required for the controlling it.
4) To recommend measure if implemented will lead to effective control of erosion in a construction
1.4 RESEARCH QUESTIONS
The study sought to answer the following research questions
1) What are nature and various causes of erosion in settlements in Agbor?
2) What are the process to be applied in erosion control?
3) What are the various types of materials to be used in controlling erosion?
4) If implemented will lead to effective control of erosion in an erosion prone site?
1.5 SIGNIFICANT OF THE STUDY
The significance of this study shall include the follow:
1) Contractors and engineers shall know how to control erosion in an erosion prone site.
2) The engineers and the general public will because more aware on the importance of erosion control in a site.
3) Lecturers, students consultants and other stakeholders in the construction industry will be theoretically & technically equipped on how to control erosion in an erosion prone construction site.
1.6 STUDY OF AREA
This study was delimited to the problem of erosion in a site prone to erosion. It focused on the type and magnitude of erosion at site in Delta state and also looked at the specific remedial techniques to that building site will function effectively and efficiently. Attempt should be made to look into laboratory experimentation of the material used for effective control of erosion in settlements prone to erosion. Agbor erosion is gully erosion-gully erosion is of concern due to periodically intense rainfall and a large average of erodible soils. Effective design of gully control system must consider the gully network as a whole and be based on geomorphologic indicators such as type of network, order and stage of development.
1.7 DEFINITION OF TERMS
According to Grolie (1990). Erosion is the wearing away of the earth surface by the action of water.
According to Milos Holy (1987). Building is permanent or temporary structure enclosed within exterior walls and a roof and including all attached apparatus. Equipment and fixtures that cannot be removed without cutting into ceiling floors or walls. In the year 1960 Bernard Huss define soil as the top layer of the earths surface in which plants an grow consisting of rock and mineral particles mixed with decayed organic matter and having the capability of retaining water.