Effective Ways of Controlling Erosion in a Building Site in Selected Sites

EFFECTIVE WAYS OF CONTROLLING EROSION IN A BUILDING SITE IN SELECTED SITES IN EKWULOBIA ANAMBRA STATE

Bernard Huss (1953) defines erosion as something that takes away the five soil rich in plant-food. The word erosion means” gnawing away” and has the same root as hats or mice, but in soil erosion the thing which is engaged in gnarring is the farmers greatest friend, the water which however, can also become his greatest energy. If not properly managed. Thing which is being gnawed away by water is the soil. It is done by the water flowing over loose soil and taking it along with it. It is usually the line soil, rich in plant-food. That is carried away and this we can say that with every rain the cream of our soil is being slowly taken off and carried away down to the sea never to return.

According to Robert. M. (1984) opined that erosion is manifested by the deterioration of soil surface effected by exogenous forces. Especially water, ice wind and man as the significant anthropogenic factor. The disturbance of the soil surface accompanied by the removal of the detached soil particles by the force of kinetic energy of some of the erosion agents, namely water and wind and the deposition of this matter with a decrease in this energy.

2.2     CLASSIFICATION OF EROSION

Turn bull W.J. classified erosion as follows in the year (1987).

i         Erosion by water

ii        Erosion by glacier

iii       Erosion by snow

iv       Erosion by wind

v        Anthropogenic erosion

The said types of erosion may occur separately or in combination causing erosion of varying intensity. On the word scale greatest damage to the economy comes form water and wind erosion whose unfavorable effects are increased by anthropenic erosion.

A       WATER EROSION

Water erosion is caused by the kinetic energy of rain drop impinging on the soil surface and by the mechanical force of surface nun off. Surface nun off is caused by heavy rainfall, of long duration snow water form spring throw and the concentration of water in the natural or artificial hydrographic network. Bank erosion is effected by the water of sacs, lakes and pounds, ground waters, namely water form karsts formation cause not only mechanical but also chemical erosion other types of mechanical erosion are evolution and abrasion of the bank and bed rock water flows, lakes and seas.

B       GLACIER EROSION

Glacier erosion is caused by a glacier moving by force of gravity into the valley, thereby eroding the bedrock which it grinds and wears, and cuts by boulders frozen in the glacier. It removes and transports into the valleys detached weathered rock which when deposited from moraines. Are transported into water flow by water from throwing glacier considerably contributing to the salting of these flows

C       SNOW (RIVAL) EROSION

Is caused by the movement of show in form of avalanches whose erosion activity takes place high pressure and velocity. The avalanche usually devastates the affected area show erosion may also be caused by the slow movement of a layer show along on unfrozen soil surface during the spring throw. This type of erosion mainly affected sub mountain area.

D       WIND EROSION

Is evident by the removal soil particles by the force of the kinetic energy of wind. These soil particles are transported and deposited when the energy of wind flow drops.

2.3     CLASSIFICATION OF EROSION BY FORM

The form of erosion are derived from the effort of exogenous agent on the soil surface  erosion and under the soil surface – sub-surface erosion.

Surface water erosion

–        Sheet erosion

–        Hill and gully erosion

–        Stream erosion

A       SHEET EROSION

Sheet erosion is characterized by the detachment and removal of soil more or less evenly over the whole affected area. The first stage of sheet erosion is selective erosion when surface num-off removes fine soil particles and the chemical substances which they bind. The soil texture changes as done the soil nutrient content. Soils exposed to selective erosion becomes coarse grained and have a significantly lower nutrient content while the soil enriched by the sediments are fine grained and rich in soil nutrient selective erosion is a low process, very often inconspicuous and without any visible enacies. It becomes obvious when fine grained material accumulates in the lower part of slopes namely often heavy rain  this fine grained material often silts ditches and communication. Selective sheet erosion causes an uneven development of the vegetation which is manifest in its growths. Colour and quality on those parts of the slope which have been exposed to the washing of fine grained soil particles and nutrients and in the lower part of slope where washed fine grained soil particles have accumulated. Selective erosion may reliably be ascertained by the texture analysis of the soil and by the measurement of changes in the soil nutrient content in different point of the slope the removal of soil in thin lay is caused by num-off with a higher kinetic energy and the unfouorable formation of soil profile, ie the alternation of soil wash is evident either evenly on the whole slope or in broad strips depending on the soil surface relief. It usually results in the total loss of top soil concentrated surface num-off hills and grooves the soil surface and gradually cuts deep gullies into the soil surface.

In the first stage small narrow channel are cut into the soil surface which create a sense network on the affected slope or shallow winder channels which are so dense continuing erosion and the further concentration of surface num-off cuts deeper channels into the soil surface i.e hills which gradually merge and deeper and become gullies.

Gullies erosion may then gradually develop into dangerous and devastating ravine erosion.

There are basically two types of gullies. In areas where the sub soil layers and the bedrock are more resistant to be effect of water than are the surface layers, gullies and navies are format with sloping side v-shaped bottom. In area with equally resistant layers in the wholes soil profile, e.g in alumna clays or Aeolian loess soil gullies and navies are formed which have verticals sides with broad U-shaped bottom water flowing over the heads and side of gullies and having is termed water fall erosion and it often depend on the channel of the foot of the water fall and bank owe undermined and caved in. gullies and navies often affect aquifer reducing the ground water level and drying up the surrounding area. Stream erosion is caused by the stream in water causes the stream will either crude the bad or the bank of the stream channel bad erosion is a form of longitude erosion proceeding along the longitudinal axis of water flow while bank erosion is a form of universal erosion proceeding normally to the flow axis. The stream erosion is most evident in torrent which usually carry large amount of sediments.

2.4     CLASSIFICATION OF EROSION BY INTENSITY

Erosion intensity is usually expressed by the detachment and transport of soil in weight or volume units, in some cases by the thickness of the layers of transported water per unit of area per unit of time. The intensity of gully erosion is often measured by the density of hills, gullies and navies expressed by their length per unit of area. By its intensity erosion may be classified as normal and abnormal i.e accelerated. In normal erosion process intensity is low and loss of soil particles is offset by the formation of new soil particles form paternal substrate. The thickness of the soil profile is not reduced and the texture of the surface soil  changes and becomes course grained. Normal erosion include seasonal manifest when soil is covered with crops that gives small protective cover and micro erosion which causes the detachment of soil particles and plant nutrient form local elevation and their transportation to smaller distance. Seasonal erosion is manifest by a temporary decrease in soil fertility micro erosion by a varied yield of crops. The wash of soil particles caused by accelerated erosion is such that there can no longer be any natural soil replacement from the paternal substrate. The result is a sharply modeled surface. It is extremely difficult to determine the permissible erosion rate which is given by erosion intensity because it must always be considered with regard to the possible consequence of the erosion process in the condition.

In agriculture the permissible erosion limit is considered as being that intensity which allows the formation of new soil and does not reduce current soil fertility.

2.5     CAUSES OF EROSION

Erosion is caused by surface num-off and result complex natural process. Erosion is caused by rainfall and by surface num-off and is affected by a number of natural and anthropogenic agent it may be expressed as the relation between the erosive of rain fall, i.e the susceptible of the soil to erosion.

Water erosion is caused by precipitation. Area with a low precipitation usually have  small surface num-off because precipitation water infiltrates into the soil is consumed by vegetation.

In mountainous area erosion may be caused by over gazing which result in the denudation of the soil surface. Grazing live stock, especially sheep. Trail the land these trials become num-off path hills, which further erosion turn into gullies and navies high ways roads and rail ways also         contribute to the development of erosion their unconsolidated and often sheep embankment and shoulder are significantly disturbed by num-off.   The detached particles are transported into drainage ditches where they are deposited thereby silting and dogging them.

Urbanization and the construction of housing estate often result in more intensive erosion than does intensive agriculture. The soil surface is denuded on large area. It is trampled and compacted to such an extent that no longer allows water to infiltrate into the deeper layers heavy machinery disturbs the surface even more and groove the whole building site which result in even more intensive erosion. Erosion is caused by running (water and wind erosion in area with open cost running) it is also caused by waste disposal heaps, to rest passes cut for the construction cable-line ski-tous in mountains area.

Planted with vegetation which gives the soil small protection these areas are exposed to the kinetic energy of rain drupe and affected by surface num-off which result in intensive erosion mainly on land slopes, heavy machinery used on the farm disturbs the soil structure and diminishes the infiltration capacity of soil. Unsuitable designed road network form num-off paths for water and are the basis for future hills and gullies. Unsuitable built drainage system in hill area have similar negative effects. Mineral fertilizers, pesticides and other chemical which are washed and blown into resources which they pollute.

Erosion may also be broadly cause by a natural factor organ

–        The nature of land scope

–        The nature of the soil

–        The nature of the rock or geologic unit

–        The nature of the surface water or ground water.

A       THE NATURE OF THE LAND SCOPE

Whether the area is lily or sloppy area it is usually gully erosion (it is usually  referred to as the   to zoography of the soil e.g where a slop exceeds 1:10 in gradient, it become dangerous in building one to con means that tan o = 1/10 problem of  such is excessive num-off force. Flood water erode the area are in tow forms of erosion types. One is sheet erosion while the other is gulley erosion. Both of which are dangerous. Sheet erode the whole area sheet by sheet until the soil expose. While gully erosion eaves out channels which widen and depend to a dangerous depth forest and building cave in that area are swallowed by the gully. (check the case of Ekwulobia erosion site).

B       THE NATURE OF SOIL

For the nature of soil we have different types of soil such as sandy clay. Limestone. Chalk formation etc the porosity and permeability of the erosion e.g clay will be eroded more compare to sandy soil while lime stone. Chalk formation is the most dangerous type of soil.

Limestone is calcium carbonate (ca C03) while chalk is derived from calcium oxide (CaO) both of these are soluble in water. When there is a large scale formation of either underground. It is a dangerous area to build on this is because of action of rain and food water this formation is gradually dissolved away leaving a very deep hallow space.

 

C       THE NATURE OF THE ROCK OR GEOLOGIC UNIT

Such as igneous, sedimentary and metamorphic rock. The sedimentary rock will be prone to erosion because they are made of soluble material and arranged in layers which can be easily broken down. The geological unit simply mean. What the rock is made up of, the rock may be made of clay or sand. They made up of sand is more prone to erosion.

D       THE NATURE OF THE SURFACE WATER OR GROUND WATER

The nature of the surface H2O and grand H20 charactistics are embodied in the hydrologic cycle. So the intensity of precipitation of water (H20) which normally affect the rate of surface erosion is connected with the hydrologic cycle pure water pressure, seepage factor that contribute to surface erosion

–        Anthropogenic erosion is caused intensified agriculture, the building of communication and urbanization rank, mining deforestation etc.

2.6     THE REMEDIES FOR SOIL EROSION

1)      Conservation of bush and a forestation.

According to Bernard Huss 1953, 61 He said we should save the native bush and forest from being destroyed. Nature has provided our beautiful country with all necessary natural means of keeping the soil intact by covering it with bush and forest.

In many places. Therefore, any further thoughtless destruction should stopped and tree-planting be more and more encouraged and extended.

2)      Cutting instead of Burning Grass.

Grass burning should be reduced in extent and where necessary carried out more judiciously. As the country becomes more heavily stocked it will be necessary to preserve as hay or winter fodder much of the grass which is so extravagantly burned to day.

3)      Protect the River Banks

In nutrias every rive is protected, and according to its flow a belt raining from 25 to 50 feet on each side is preserved by low. The natural vegetation growing on river bank is a protection wisely provided by nature against erosion in time of flood.

4)      Not too many footpaths.

Roads should be properly drained, and formers should compel evaveller to use the public road or properly hoarded footpath.

B       DAMMING THE DONGAS

Any dongas or gully already existing and not quite beyond human control should be blocked by darus of earth or stories placed  across it, or by planning willow posts. Popular suckers and other things at the bottom end of the shut, as than sand and nebbish will bank up against these and gradually fill up the deep channels. Here as in other case it is good to remember that prevention is better than cure.

 

 

C       EROSION CONTROL

According to Milosholy (1950-154) He said that Erosion control is indispensable in view of the expanding economic activity of society and the endeavour to use natural resources purposefully and economically. The object of erosion contact is to protect the two mostly valuable natural resource. The water and soil and to prevent the occurrence of the unfavorable consequence which their deterioatetion could have for various branch of the natural economic, namely for agriculture and water management and for the human environment.

The basic demand placed on erosion control is that it should be comprehensive. Any evaluation of water erosion process and any erosion control scheme should conceive that catchment as being the basic unit in which an organic system of measures may suitable modify num off condition.

D       AGRICULTURAL AND FORESTRY MEASURE

Agricultural and forestry techniques used for erosion control exist in the correct location of cultures a well designed layout of plots and communication system, correct cultivation of field and forest solid and the use of the protective effects of the vegetative cover.

The location of culture has immense influence on the origination and course of surface nun off and on soil erosion resistance.

Different culture provide different condition for infiltration of precipitation into they soil by their root systems, they enrich it with organic residues thereby upgrading its physical chemical and biological properties they shade the soil prevent the occurrence of excessive evaporation they affect wind flow in the ground layer of the atmosphere etc. in on area susceptible to erosion the location of culture must therefore be totally subordinated to the demand of erosion control. This is affected by the relief of the area. Water divide area slopes and valleys have different hydrological and soil properties which determine the suitability of culture and choice of cultivation techniques used. After divides which cover the highest affected areas are characterized by rough grained permeable soil which absorb precipitation which infiltrate into the deeper layers and flows out as subsurface nun off the water divide is therefore on suitable site for deep rooting culture such as forests and groves which by turning surface nun off into subsurface nun off effective erosion control. Soil permeability usually decrease down hill and surface nun off occurs no larger.

The smallest recommended depth of terrace is 0.5m bank slope 1.5 (or better 1:10) to allow machinery to traverse and the minimum area of the cross profiles 0.8m2. Standard rain is usually selected with periodicity.

P       =       0.1     duration

+       =       is min and nun off coefficient 0 is obtained from equation cultivated broad base terrace are established along the contour or are parallel and installation may be built to limit the longitudinal movement of water the choice of terrace is given by the configuration of the terrain figure 8 and 9.

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