Introduction
The environment today is in a dynamic state (always changing) due to man’s various activities. Man has the ability to alter the natural state of the environment but he cannot do without the environment as a result of finding means of survival and also performing his socio-cultural activities. However, these various activities of man lead to degradation and erosion which has resulted to loss of lives and properties in various parts of the world. It is important to note that without the land (soil), plants cannot survive, without plants life cannot be sustained and without land, man cannot survive.
Umoru (2001) observed that man has contributed greatly to this environmental problem in many ways by constructing road without drainage system, indiscriminate disposal of solid waste and also building houses against the wind and water channels resulting to several collapse of buildings, loss of lives and properties including flooding etc. Soil erosion has being in existence since the evolution of the earth and it has existed for as long as water has been on earth. The bid to maintain a sustainable environment has been the priority of man despite finding means of survival.
Therefore in other to examine and find solution to the problem of land (soil erosion)erosion in man’s environment, efforts should be made, using the available and affordable materials to study and access the prevailing situation so as to provide a satisfactory and lasting solution to avert its health implication.
The word erosion is derived from the Latin word “erosio” meaning “to gnaw away”. In general terms, soil erosion implies the physical removal of topsoil by various agents including rain, water flowing over and through the soil profile, wind, ice or gravitational pull. The consequences of soil erosion can be seen both on-site and off-site. On-site effects are the loss of soil, the breakdown of the soil structure and the decline in organic matter. Erosion also reduces available soil moisture, resulting in more draught prone conditions. Off-site effects or problems result for sedimentation downstream or downwind which reduces the capacity of rivers and drainage ditches, increases the risk of flooding, blocks irrigation canals, and shortens the design life of reservoirs. The effects of soil erosion although temporarily masked by modern technologies are evident by the high cost of producing and maintaining waterways, reservoirs and harbours. Therefore, for erosion control measures, it is necessary to know why and how erosion occurs.
Definition of soil erosion
According to Ojebor (1996), soil erosion is the removal of uppermost layer of the earth surface. This process is carried out by agent of denudation e.g. water, wind, wave etc. it has led to flooding which invariably lead to disaster. Umoru (2001) defines soil erosion as the wearing away of the land surface by various natural agent such as water (e.g. sea, river rain) ice and wind. It is the wearing away of the topmost part of the earth crust.
Soil erosion is the process by which soil and rock are removed from the earth’s surface by exogenic process such as wind, ice, water, etc. It is part of the process of denudation which besides the wearing away of rock and also involved the transportation and eventually depositing the sediments. Encyclopedia American Int. (2004). Olemeforo and Obasi (1999) gave their own perspective that soil erosion is one of the most visible land degradation features in Nigeria with; particular reference to the southern and eastern part of Nigeria.
Man due to his quest for survival and also performing his socio-cultural activities has degraded the environment where he lives and it is now increasingly evident that more and more disease form from the degradation caused by man and its environment. Therefore all over the world, it is now recognize that the use of soil (land) must be planned and that land must be properly managed. It is to continue to support its (soil) existence, its properties, and livestock and give the maximum yield of crops that can sustain man.
Causes of soil erosion
In Nigeria various factors are contributing to soil erosion. Olemeforo and Obasi (1996) opine that the causes of erosion may be classified into two (2):
- Physical and natural factors
- Dull ropogenic or man—induced causes.
However, none of the above factors is naturally exclusive in its operation or operates in isolation without the other, rather both factors operates together in most places where soil erosion is identified.
Among the physical factors, the following sub-factors are often identified.
- The characteristics and structure of rock
- Climate
- Hydro geological condition
- Flood and Topography
- Climate
- Hydro geological condition
- Flood and Topography
According to Ojebor and Ilayah (1996), human activities which have accelerated soil erosion in Nigeria include wrong crops cultivation or agronomy practices, quarrying and some other mining operation road construction without provision for drainage system, deforestation, use of footpath, over grazing, tramping by livestock and uncontrolled bush burning to mention but a few.
Umoru (2001) opined that coastal erosion may be caused by the following factors:
- Removal of sand from the beach
- Heavy rainfall
- Blockage of drain and leads of drainage channels.
Effects of soil (land) erosion
According Ajayi (1998) soil or land erosion leads to loss of lives and properties as it happened in Ibadan in recent years. It can also lead to the land and water pollution through dispersal of waste indiscriminately. According to Ojugbeli (2004), to identify water pollution, it is good to know the source of water supply and types of water borne diseases which are dangerous to health of man such as cholera, typhoid fever, dysentery etc. the effects of soil erosion thus include;
- Destruction of feeder road
- Reduction of nutrient in soil.
- Damage to building, property, water and farmland.
- Damage to building, property, water and farmland.
- Destruction of lives and properties
- Unwanted spending of money through the relocation of people who live near erosion places.
Health hazards that are associated with soil erosion
According to Ichidi (2008) the health hazards associated with soil erosion are:
- Disease infestation
- Flood
- Physical disaster
- Disease infestation: Erosion and its association pollution and dirt (refuse), have been veritable actors in the spread of infestation of diseases. The pollution of water by soil erosion has consequently made water to be unfit for human consumption. So lat any attempt made by using the polluted water is always resulting to disease infestation.
- Flooding: According to Olemeforo (1999), the term flooding can be described as a situation where a river channel is inadequate to accommodate discharge from the catchments. Flooding has become a common feature in all the geographical region of Nigeria in recent time as well as other part of African and the entire world.
- Physical disaster: Soil erosion in Nigeria and beyond has caused a lot of physical disasters. Examples include the collapse of Bagade Dam near Kano as reported in National Concord of August 19, 1988; in which 18,000 houses were destroyed and over 10,000 people were rendered homeless and similar incidence also occurred in Ibadan where 30 people lost their lives and 10 houses destroyed about 15,000 people homeless. A global record of devastating effect of erosion has been kept. In November, 1999, it was reported by Guardian News paper that erosion in Vietnam devastated the central province of the region and about 550 people lost their lives and properties worth 200 million dollars.
Control measures for soil erosion
These include the following;
- Health education to the public on the harmful effects of erosion.
- Making ridges and cross slopes
- Controlling overgrazing of lands
- Use of environmental laws and policies
- Planting cover crops such as legumes, melon and cowpea
- Fallowing of farmland should be encouraged
Ojewale (2003) said that there is need to protect health and environment, to minimize the burden of future generations and that government should intensify environmental education more than ever before, to curb environmental degradation, destruction, distraction and disruption resulting in land erosion desertification and other natural health hazards and risk. Finally, Jeered (1997) opined that erosion is sometimes difficult to control because of inefficient tools, labour force and poor planning strategies but proper town planning through the help of town planners will help to control soil erosion.
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