General

The role of indiscriminate refuse disposal in soil erosion

Introduction

Soil erosion is the displacement of the upper layer of soil, one form of soil degradation. A low level of erosion of soil is a naturally occurring process of all land. The agents of soil erosion are water and wind, each contributing a significant amount of soil loss each year. Soil erosion may be a slow process that continues relatively unnoticed, or may occur at any alarming rate causing a serious loss on topsoil. The loss of soli from farmland may be reflected in reduced crop production potential, lower surface water quality and damaged drainage networks (Akolkar, 2008).

Asani (2014) stated that human activities have increased by 10-40 times the rate at which erosion is occurring globally. Excessive (or accelerated) erosion causes both “on- site” problems. On site impacts include decreases in agriculture productivity and (on natural landscapes) ecological collapse, both because of loss of the nutrient-rich upper soil layers. In some cases, the eventual end result is desertification. Off site effects including sedimentation of waterways and eutrophication of water bodies as well as sediment related damage to roads and houses. Water and wind erosion are the two primary causes of land degradation; combined, they are responsible for about 84% of the global extent of degraded land, making excessive erosion one of the most significant environmental problems worldwide.

Intensive agriculture, deforestation, roads, anthropogenic climate change and urban sprawl are amongst the most significant human activities in regard to their effect on stimulation erosion. However there are many prevention and remediation practice that can curtail or limit erosion of vulnerable soils. (Barbalace, 2009).

Refuse refers to solid waste materials generated by man from day to day activities. This refuses if not properly handle can trigger the occurrence of erosion (Ajabor,2016).

Physical processes of soil erosion

According to Davidson (2011) the physical processes of soil erosion encompasses the following:

1 Rainfall and surface runoff

2 Rivers and Streams

3 Floods

Rainfall and surface runoff

Rainfall and the surface runoff which may result from rainfall, produces different types of soil erosion (Davidson, 2011).

River and streams

Valley or streams erosion occurs with continued water flow along a linear feature. The erosion is both downward, deepening the valley, and head ward, extending the valley into the hillside, creating head cuts and steep banks. In the earliest stage of stream erosion, the erosion activity is dominantly vertical, the valleys have a typical v cross section and the stream gradient is relatively steep. When some base level is reached, the erosion activity switches to lateral erosion, which widens the valley floor and creates a narrow floodplain. The stream gradient becomes nearly flat, and lateral deposition of sediments becomes important as the stream meanders across the valley floor. In all stages of stream erosion, by far the most erosion occurs during times of flood, when more and faster moving water alone that erodes: suspended abrasive particles, pebbles and boulders can also act erosively as they traverse a surface, in a process known as traction (Lardionois, 2008).

Bank erosion is the wearing away of the banks of stream or river. This is distinguished from changes on the bed of the watercourse, which is referred to as scour. Erosion and changes in the form of river bank may be measured by inserting metal rods into the bank and marking the position of the bank surface along the rod at different times (Pierre, 2010).

Floods

At extremely high flows, kolks, or vortices are formed by large volume of rapidly rushing water. Kolks cause extreme local erosion, plucking bedrock-cut basins. Examples can be seen in the flood region result from local glacial Lake Missoula, which created the channeled scablands in the Colombia Basin region of eastern Washington (Destiny, 2016)

Mass movement of sediment

Mass movement is the downward and outward movement of rock and sediments on a sloped surface, mainly due to the force of gravity. Mass movement is an important part of the erosional process, and often the first stage in the breakdown and transport of watered materials in mountainous areas. It moves material from higher elevations to lower elevations where other eroding agents such as streams and glaciers can then pick up the material and move it to even lower elevations. Mass- movement processes act very slowly; others occur very suddenly, often with disastrous results. Any perceptible down-slope movement of rock or sediment is often referred to in general terms as a landslide. However, landslides can be classified in a much more detailed way that reflects the mechanisms responsible for the movement and the velocity at which the movement occurs. One of the visible topographical manifestations of a very slow form of such activity is a screen slope (Ministry of urban development and Poverty Alleviation [MOUDPA], 2011).

Types of erosion

According to Destiny (2016), there are four main types of erosion which include;

Splash erosion
Sheet Erosion
Rill Erosion
Gully Erosion

Splash erosion

In splash erosion, the impact of a falling raindrop creates a small crater in the soil, ejecting soil particles. The distance these soil particles travel can be as much as 0.6m (two feet) vertically and 1.5m (five feet) horizontally on level ground. If the soil is saturated or if the rainfall rate is greater than the rate t which water can infiltrate into the soil, surface runoff occurs. If the runoff has sufficient flow energy, it will transport loosened soil particles (sediment) down the slope.

Sheet erosion

Sheet erosion is the transport of loosened soil particles by overland flow.

Rill erosion

Rill erosion refers to the development of small, ephemeral concentrated flow paths which function as both sediment source and sediment delivery systems for erosion on hill slopes. Generally, where water erosion rates on disturbed upland areas are greatest, rills are active. Flow depths in rills are typically of the order of a few centimeters (about an inch) or less and along-channel slopes may be quite steep. This means that rills exhibit hydraulic physics very different from water flowing through the deeper, wider channels of streams and rivers.

Gully erosion

Gully erosion occurs when runoff water accumulate and rapidly flows in narrow channeled during or immediately often heavy rains or melting snow removing soil to a considerable depth.

Factors affecting soil erosion

Climate

The amount and intensity of precipitation is the main climatic factor governing soil erosion by water. The relationship is particularly strong if heavy rainfall occurs at times when or in locations where the soil’s surface is not well protected by vegetation. This might be during period when agricultural activities leave the soil bare, or in semi-arid regions where vegetation is naturally sparse. Wind erosion requires strong winds particularly during times of drought when vegetation is sparse and soil is dry (and so is more erodible). Other climatic factors such as average temperature and temperature range may also affect erosion via their effect on vegetation and soil properties (Olojoba, 2009).

Soil structure and composition

Vegetative cover

Vegetation acts as an interface between the atmosphere and the soil. It increases the permeability of the soil to rainwater, thus decreasing runoff. It shelters the soil from winds, which results in decreased wind erosion, as well as advantageous changes in micro climatic. The roots of the plants bind the soil together and interweave with other roots, forming a more solid mass that is less susceptible to both water and wind erosion. The removal of vegetation increases the rate of surface erosion (Unuraye, 2007).

Topography

The topography of the land determines the velocity of which surface runoff will flow, which in turn determines the erosivity of the runoff. Longer steeper slopes (especially those without adequate vegetative cover) are more susceptible to very high rates of erosion during heavy rains than shorter, less steep slopes. Steeper terrain is also more prone to mudslides, and other forms of gravitational erosion processes (Unuraye, 2007).

Human activities that increase soil erosion

Agricultural practices

Unsustainable agricultural practices are the single greatest contributor to the global increase in erosion rates. The tillage of agricultural lands, which breaks up soil into finer particles, is one of the primary factors. The problem has been exacerbated in modern times, due to mechanized agricultural equipment that allows for deep plowing, which severely increases the amount of soil that is available for transport by water erosion. Others include mono-cropping, farming on steep slopes, pesticide and mechanical fertilizer usage (which kill organisms that bind soil together), row-cropping, and the use of surface irrigation. A complex overall situation with respect to defining nutrient losses from soils could arises as a result of the size selective nature of soil erosion events, loss of total phosphorus for instance in the finer eroded fraction is greater relative to the whole soil (Blanco & Lal, 2010).

Deforestation

In the undisturbed forest, the mineral soil is protected by a layer of leaf litter and humus that cover the forest floor. The two layers form a protective mat over the soil that absorbs the impact of rain drop. They are porous and semi permeable to rainfall, and allow rain water to slow percolate into the soil below, instead of flowing over the surface as runoff. The roots of the trees and plants hold together soil particles, preventing them from being washed away. The vegetative cover act as reduced the velocity of the raindrops that strike the foliage and stems before hitting the ground, reducing their kinetic energy. However it is the forest floor, more than the canopy that prevents surface erosion (Torrence, 2012).

Roads and urbanization

Urbanization has major effects on erosion processes first by denuding the of vegetative cover, altering drainage patterns, and compacting the soil during construction, and next by covering the land in an impermeable layer of asphalt or concrete that increases the amount of surface runoff from urban areas( especially roads) is highly contaminated with fuels, oil, and other chemicals. This increased runoff, in addition to eroding and degrading the land that it flows over, also causes major disruption to surrounding watersheds by altering the volume and rate of water that flows through them, and filling them with chemically polluted sedimentation. The increased flow of water through local waterways also causes a large increase in the rate of bank erosion (Destiny, 2016).

Climate change

The warmer atmospheric temperatures observed over the past decades are expected to lead to a move vigorous hydrological cycle including more extreme rainfall events. The rise of sea levels that has occurred as a result of climate change has also greatly increased coastal erosion rates. Studies on soil erosion suggest that increased rainfall amounts and intensities will lead to greater rate of soil erosion. Thus, if rainfall amounts and intensities increase in many parts of the world as expected, erosion will also increase unless amelioration measures are taken. Soil erosion rates are expected to change in response to changes in climate for a variety of reasons (Borah, 2008).

Environmental impact of soil erosion

Due to the severity of its ecological effects, and the scale on which it is occurring, erosion constitutes one of the most significant global environmental problems we face today and these include;

Land degradation: water and wind erosion are now the two primary causes of land degradation; combined, they are responsible for 84% of degraded acreage. Each year, about 75 billon tons of soil is eroded from the land a rate that is about 13- 40 times as far as the natural rate of erosion. Approximately 40% of the world’s agricultural land is seriously degraded. According to the United Nations, an area of fertile soil the size of Ukraine is lost every year because of drought, deforestation and climate change. In Africa, if current trend of soil degradation continues the continent might be able to feed just 25% of its population by 2025, according to UNU’s Ghana- based institute for national Resources in Africa. The loss of soil fertility due to erosion is further problematic because of response is often to apply chemical fertilizers, which leads to further water and soil pollution, rather than to allow land to regenerate (Ritter, 2008).

Sedimentation of aquatic ecosystems: soil erosion (especially from agricultural activity) is considered to be leading global cause of diffuse water pollution, due to the effects of the excess sediments flowing into the worlds waterways. The sediments themselves act as pollutants. As well as being carriers for other pollutants. Such as attached pesticide molecules or heavy metals. The effect of increased sedimentation loads on aquatic ecosystems can be catastrophic. Silt can smoother the spawning beds of fish, by filling in the space between gravel on the stream bed. It is also reduces their food supply, and causes major respiratory issues for them as sediment enters their gills, the biodiversity of aquatic plant and algal life is reduced, and invertebrates are also unable to survive and reproduce. While the sedimentation event itself might be relatively short-lived, the ecological disruption caused by the mass die off often persists long into the future(Borah, 2008).

Airborne dust pollution: Soil particles picked up during wind erosion of soil are a major source of air pollution, in the form of air particulates “dust”. These airborne soil particles are often contaminated with toxic chemicals such as pesticides or petroleum fuels, posing ecological and public health hazards when they later land, or are inhaled/ingested. Dust from erosion acts to suppress rainfall and changes the sky color from blue to white. Which leads to an increase to red sunsets? Dust events have been linked to a decline in the health of coral reefs across the Caribbean and Florida, primarily since the 1970s. Similar dust plumes originate in the Gobi desert, which combined with pollutants, spread large distances downwind, or east wind, into North America (Ritter, 2008).

The role of indiscriminate refuse disposal in soil erosion

Refuse result from man’s day to day activities and its effect on man and the environment is critical. Flooding happens from time to time either due to heavy rainfall or overflows of dams or rivers which eventually results to soil erosion. The mass generation of refuse by man is a major concern as it results to soil erosion indirectly (Destiny, 2016).

Refuse are dumped indiscriminately into water bodies, around the environment and end up in our drainage systems. When refuse are dumped indiscriminately in drainage systems, they accumulate and result to blocked drains thereby preventing the free flow of water which eventually will lead to accumulation of water and then to soil erosion. When drains which are supposed to arrest waste water are covered by refuse the water tends to flow across the soil leading to soil erosion (Herbert, 2016).

More so, dumping of refuse into water bodies gradually increases water level as much refuse may not dissolve in water, when this continues for so long, the water level of such water body increases gradually and sooner or later it will overflow and lead to soil erosion.

Again, the indiscriminate disposal of refuse will restrict the movement of water to a particular channel and thus cutting into the soil, when refuse occupy areas where water should have passed into seas and ocean, the water flows right back into the environment and causes soil erosion (Blaco & Lal, 2016).

Factors that attributed to indiscriminate refuse disposal, which influence soil erosion

According to Unuraye (2007) the following factors attribute to indiscriminate refuse disposal;

Nonchalant attitude of the public: The care free attitude of people in the society today result to indiscriminate refuse disposal in the environment because people do not care about the implications that such particular refuse will result in the environment neither do they worry about their health.

Population Explosion: The rapid growth in population today in our urban cities also leads to the indiscriminate refuse dumping. The more increase of population, the more waste are generated through the activities of man.

Absence of sanitary site: The absence of refuse disposal site also leads to this problem. For instance if there is sanitary site where government approved for the public each household and individual will go and empty their dustbin in such site at regular interval which would have help to reduce the indiscriminate dumping of refuse in the environment.

Lack of law enforcement in the society: lack of implementation of environmental rules and regulations which safe guarding the health of the public in the society. Also give room to this indiscriminate disposal of refuse. This is because even if people are violating the laws, government agencies will do nothing because of bribery and corruption and lack of law enforcement.

Effective refuse disposal methods to prevent soil Erosion

According to Olojoba (2009) there are many ways by which refuse can be disposed of, these depend on the nature of refuse in the locality and availability of labor and finance. These methods includes

Sanitary landfill or controlled tipping: As the name implies it is sanitary tipping of refuse to reclaim pit low land pools ditches and well in such the deposition of the refuse is deposited in the pit and earth is also used to cover the surface at the end. It reduces the risk of fire hazard and there is no air pollution, it requires large space of land skill personal for operation.

Composting: The process of composting is the attempt to control the natural decomposition of organic matter in a warm moist environment through the action of bacteria, fungi, most other organism present in the reuse, Remnant of food is dump into a pit that is about 3 to 4 pits 1.5 meter deep to allow for rotation, It requires low capital and as a source of resource revenue to owner also manure can be used as fertilizer.

Incineration: Incineration is the burning of refuse in high temperature in a furnace called incinerator, incineration take care of only combustible refuse while the non- combustible are separated out for recycling and reuse before burning combustible material. It is an effective method to dispose hospital waste. However the residue called as that arises from the incineration should be disposed off sanitary landfill.

Others are methods of Refuse disposal but are not approved by World Health Organization these include;

Burying: Refuse like broken bottles, pots and things of all kinds etc., could be buried in a premises, one need to dig a hole sufficient to contain the refuse to be dispose of and the hole should be properly covered with earth to prevent domestic animal from rooting them up.

Burning: This method require low temperature burning of combustible refuse and this is the most frequent methods of refuse disposal on a small scare such as paper, rags, dry leaves etc mostly at the backyard. It is cheap and simple to operate; it can as well result to fire outbreak, smoke and odor Nuisance contributing to air pollution.

Conclusion and recommendations

Soil erosion is a global phenomenon, and it is triggered by certain environmental factors resulting from man’s activities and negligence of environmental concepts. If waste can be properly managed it will help to reduce the soil erosion. Waste results to blocked drains and causes soil erosion by flooding. It is therefore recommended that:

Proper health education should be done to create awareness on the need of proper refuse disposal.
Government should ensure to create a wastes management and reuse facility to encourage the recycling and reuse of waste.
Individuals should avoid disposal of waste indiscriminately in water bodies and the environment.
Adequate supervision should be carried out to ensure strict compliance with waste disposal.
Waste collectors should be constituently collect refuse from collections point at least four times a month which will help to reduce the indiscriminate dumping of refuse and maintain the aesthetic nature of the environment.

References

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Blanco, H. & Lal, (2010). Principles of Soil Conservation and Management. Accra: Springer.

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