GULLY EROSION THREAT AND NIGERIA ROAD TRANSPORTATION:A CASE STUDY OF SOUTHEASTERN NIGERIA.

Nigerian Society of Engineers Annual Conference Proceedings CANAAN 2011


GULLY EROSION THREAT AND NIGERIA ROAD TRANSPORTATION:A CASE STUDY OF SOUTHEASTERN NIGERIA.

C. J. OHAGWU, M. Eng1., B. O.UGWUISHIWU, Ph.D2., and J.N.NWAKAIRE,M.Eng3

Department of Agric. & Bioresources Engineering, University of Nigeria, Nsukka

E-mail:[email protected]@yahoo.co.uk, [email protected]

Abstract. Attention is drawn to gully erosion threats and problems in southeastern Nigeria with emphases in Enugu , Anambra and Imo State. The causes and gully erosion mechanism are also evaluated with the view of ascertaining the possible solutions to incessant road damage and pot-holes. Some spots of road damage and widespread of pot-holes on the roads were visited, its pictures taken as well as vehicular traffic rates. The basic steps to biotechnical gully control measures are highlighted and recommended thus appealing for Federal and international financial support for necessary research, data collection, design and construction works. Keyword: Gully Erosion, Nigeria Road, and Transportation. 1.0 INTRODUCTION. Transportation is a requirement for every nation-underdeveloped, developed /developing, regardless of its industrial capacity, population size, or technological advancement. Movement of goods and people (services) from one place to another is critical to maintain strong economic and political relationship among people within and outside the state. How these movements take place can be unique to location and technological development, but the requirement remains the same. Transportation derives demand from the things that it moves-it is only a valid economic force if there are valuable things to transport. The goods and services that are moved through transportation network could be grain silage, electronics, or business executives etc. The cost of moving things from one place to another are enormous, whether it is measured in currency or other values, it is typically stable over time, meaning that the relative cost of transporting a product decreases as the value of the product being transported increases. This phenomenon become important when examining nations with

weak economies (Nick Husher,2005). If the relative value of the goods transported is low, the cost overhead for transportation is high. The reason for the relatively high cost of transportand the low value of the products movedis partially self-fulfilling (Nick, 2005). Because there are few valuable products to transport, there will be no transportation infrastructure to transport them. Because there is no way to transport valuable products reliably and cheaply to places where they might be marketed, there is no incentive to produce valuable products. If there is a correlation between transport systems and economic strength, part of the reason for modern Nigeria's economic weakness is its lack of a strong transportation architecture ( Drummond-Thompson,1990). The current state of Nigerian transportation is a product of fifty years of colonial rule and mismanagement and another forty of relative neglect under self-rule. Civilian governments were often under-funded and their priorities were on maintaining regional divisions instead of maintaining transportation networks. This policy may have been self-fulfilling; by reinforcing regional divisions the appeal of inter-state and region transport infrastructure was further reduced. While some of the handful of military governments were interested in developing better transportation systems, they were often long term pipe dream-like solutions that would be solved with the anticipated funds. This is evident in the practice of National Development Plans that was never in place. In addition, there is an ever-increasing amount of stress on Nigerian road transport systems as the demand for transport services increases/rises (Oshin,1988). Finally, the Nigerian transport systems designed under colonial rule and maintained under civilian rule were poorly designed and are unable to scale up to meet greater demand, a design flaw which causes traffic congestion on roads, with mass-transport blind spot and pot-holes (Walker,1959). These pressures on the transport


systems degenerate over time as a result of climate changes and erosion menace in the region due to the ecological zone of the region. This work is expected to expose the causes and gully erosion mechanism as it affects road transportation, and also to evaluate its threats with the view of ascertaining the possible solutions to continuous road damages and pot-holes. 2.0 BASIS OF EROSION METAMORPHOSIS The process by which soil particles are detached from some locations, transported and deposited at other locations by climatic agents such as rain water and wind is often referred to as soil erosion. The two major types of soil erosion are geological erosion and accelerated (or man influenced) erosion. Geological erosion includes soil-formation as well as soil distribution processes that maintain the soil in a favourable balance, suitable for the growth of most plants (Schwab et al, 1981). Accelerated erosion refers to erosion process influenced by mans (human) activities. Any human activity that destroys the protective natural vegetation, leaving the soil surface bare predisposes it to accelerated erosion. Examples of agricultural activities that lead to accelerated erosion include uncontrolled bush burning, inappropriate land clearing methods as seen in road construction, improper tillage practices, over-grazing and pulverization of the soil along animal tracks by their hooves. Soil erosion by water is classified as splash, rill, gully and stream channel erosion. Splash (or rain drop) erosion results from the impact of falling rain drops directly on wet soil or thin water surfaces. As runoff from rainfall concentrates in surface depressions, sufficient soil may be removed to form small but well-defined channels. At the initial stage when these channels do not seriously interfere with normal tillage operations/ Agricultural activities, they are called rills. Rills are often ignored till they develop into gullies, the stage at which they cannot be smoothed over by normal tillage operations. Soil removal from stream banks or soil movement in the stream channel is known as stream channel erosion. 4.0 CAUSES AND MECHANISM OF GULLY EROSION Unless we clearly understand the cause and nature of any problem, any attempt to solve

the problem is usually a guess work. The major factors affecting soil erosion are climate, topography, vegetation and soils. The major climatic factors influencing runoff and erosion are rainfall, temperature and wind. Of these three, rainfall is most significant. To control any form of soil erosion by water in any location, we need rainfall data of the location. The erosivity of the rains of any location is the potential ability of the rain to detach soil particles from one part of the watershed and transport them to another part of the watershed. The erodibility of the soils in a location is the vulnerability or susceptibility of the soil particles to detachment and transportation by the erosive forces. The physical characteristics of rainfall that contribute to the erosivity include the rainfall amount, intensity, duration, drop size, drop size distribution and terminal velocity. Two major soil properties that influence the erodibility of soils are the texture and the structure. southeast region has a friable to loose texture of soil. The rate of gully erosion depends mainly on the runoff producing characteristics of the watershed, the watershed area, soil characteristics, the alignment, size, and shape of gully; and the slope of the gully bed. The main processes in the development of a gully are waterfall erosion and channel erosion. Gullies usually start with channel erosion, essentially the scouring a way of the soil by concentration of runoff as it flows over unprotected depressions. As the scouring continues, the gully becomes longer, deeper, and wider. The extension in length is usually much faster than the widening of the gully because a greater volume of runoff passes over the gully head than over the sides. Through water fall erosion, the head of the gully wade back up stream. The water fall action scours the soil where it lands and also splashes against the face of the gully head and makes an undercutting of the base. The bottom of the face is eroded away leaving the top over hanging. When the undercutting is deep enough, the overhanging breaks off, slides down to the channel bed, and is washed down the slope by runoff. The above discussed mechanism is what is prevalent and witnessed in the region as such susceptible to the gully erosion menace due to its strategic location in Nigerian as seen in table1.0.


Table 1.0: Gully Size Distribution in South-eastern States of Nigeria. S/n state Number of

Gullies Stage of Development

Control measures

1 Abia 300 Some active/some dormant

Not successful

2 Anambra 700 Mostly active Not successful 3 Ebonyi 100 Some

active/some dormant

No record

4 Enugu 600 Some active/some dormant

Not successful

5 Imo 450 Some active/some dormant

Not successful

These ecological havoc did not leave the road transportation network in these zone alone rather it metastasized into the network with unprecedented socio-economic and political divides between people and among people. These have made the zone a difficult terrain to transport goods and services to other parts of the country as such are disadvantaged with huge investment in road construction. Some of the surveyed roads that have damaged by the gully erosion are shown below in figures 1.0-9.


Table 2: Shows the Rate of Traffic On Some Selected Road in South-Eastern States. Highway Roads(trunk A) Rate of vehicular Transportation

(Traffic/12-hours-day) Federal Road Maintenance Agency

9thMile-Opi-Makurdi Express way 1600 Relative Maintenance to rehabilitation

Enugu-Okigwe-PortHarcourt Express way

1800 Relative Maintenance to rehabilitation

Onitsha-Owerri-Portharcourt Express way

1950 Complete rehabilitation

4.0 ROAD USAGE AND DEMAND The rate of traffic of goods and services across these roads understudy as seen in Table 2 above have shown that the roads are under pressure for services with 9th Mile Opi- Makurdi express way having about 1600 traffic/day, Enugu-Okigwe-Portharcourt express way having about 1800 traffic/12-hours-day and Onitsha-Owerri-Portharcourt express way having 1950 traffic/day with attendant maintenance by Federal Road Maintenance Agency. At every point in time, these roads are undergoing some levels of maintenance- from surface asphalting to complete rehabilitation. One of the major causes of road dilapidation, all things being equal, could be either the roads are always in a high demand by the road user, or that the road constructed was not properly maintained/ constructed. Of course, every well design and constructed road should have functional drainages or the inherent nature of the area if not taken into consideration also predisposes the road to damages like pot-holes, carve-in, ditches, cracks, gallops and gully erosion insurgence. Therefore, if the causes are well articulated, then the challenges of road transportation in Nigeria can now be tackled with very low traffic accidents. 5.0 BIOTECHNICAL CONTROL MEASURES FOR GULLY EROSION ON ROADS. VEGETATION IN GULLY EROSION CONTROL Vegetation can reduce gully erosion on roads as follows: I ) Interception of rainfall by vegetative canopy, absorbing the impact of falling raindrops, thereby minimizing the dispersion of soil by energy of the rain drops.

ii) Decreasing runoff velocities by well distributed close growing vegetation thus reducing the erosive capacity of the runoff. iii) Restraining of soil movement by the knitting and binding effects of root systems in soil profile. iv) Increasing soil aeration, providing better environment for beneficial bacterial activities and other biological influences enhancing the permeability of the soil. v) Restoring soil storage capacity for rain water thus decreasing runoff through transpiration vi) Adding organic matter to the soil by plant residue thus improving aggregation and porosity of the soil which reduce runoff. By the selection of suitable plants and the use of special planting techniques an erosion resistant plant cover will be established as part of gully control measures. The plants will help stabilize the gully slopes and may also offer supplementary income to the community. Planting the sides of gullies is often difficult, because they are usually steep, unstable, and eroding. When economically feasible, the gully banks can be levelled to a gentle uniform slope by heavy earthmoving machinery before seeding or planting. Since the banks are almost sure to be infertile subsoil, some extra fertility(manure) must be added. In severely eroded and gullied areas ,trees, shrubs and woody plants are used instead of crop plants or pasture. Small and medium size gullies may often be converted into grassed water ways. A practical way to transform a gully into a satisfactory water way is to shape it and seed it to adapted species of grasses. The channel cross section should be broad and flat to keep the water spread uniformly over a wide area. Soil chutes may be successfully


used to control over falls in gullies with heads less than 3m and drainage area less than 10 hectares. A sod chute merely serves the purpose of conducting runoff water through it at a safe velocity. GULLY EROSION CONTROL BY CONTROLLING RUNOFF Another major step in gully erosion control on road is to plan the control of runoff from the drainage area. Some of the methods employed in controlling runoff are as follows: i.) Runoff retention in the drainage area. ii) Diversion of runoff around the gullied area. iii) Conveyance of runoff through the gully. Runoff Retention By design and construction of earth embankment at various strategic locations, considerable amount of runoff water can be retained in the drainage area like earth pond for community water storage reservoir. Diversion Of Runoff Around The Gullied Area With the understanding that the destructive energy of water flowing on bare soil surface is the root cause of gully erosion, the most effective gully control measure is the complete elimination of runoff into the gullied area and converting the gully area into forests or grasslands (Michael and Ojha, 2003). Terraces and diversion ditches are commonly used to divert runoff from its natural outlet. Terraces are effective in the control of small gullies on cultivated fields or even medium size shallow gullies. Conveying Runoff Through Gullies If it is not possible to retain runoff in the watershed area or divert it from the gully area, then care will be exercised in conveying it through the gully. Bio-technical gully erosion control methods involve establishing vegetation on gully banks and beds designing and installing mechanical structures at critical points to give primary or supplementary control. TEMPORARY STRUCTURES FOR GULLY EROSION CONTROL Structures are used in gully erosion control especially insurgence scouring road banks to facilitate the establishment of vegetation or to provide protection at points that cannot be adequately protected in any other way. They are usually used in gullies through which the runoff must be conveyed. These structures are mostly

various types of dams constructed for the purpose of stabilizing the grade and reducing runoff velocities. When the runoff is not excessive and can be controlled by a well-stabilized vegetation, temporary structures may be used in the gullies until the vegetation is established. Temporary structures are made of locally available materials like brush, poles, woven wire, loose rock and plants or slabs ,even stockpiles of sand in bags. 6.0 CONCLUSION AND RECOMMENDATIONS Whenever the erosion power of rainfall and runoff overcome the inherent resistance of soil in any location lacking adequate vegetative cover soil erosion starts. The situation of many parts of southeastern Nigeria favour the development of gully erosion and as such the road transportation network was not left in isolation rather it is also under threat of gully erosion. Southeastern part of Nigeria needs a unique blueprint /standards for construction companies coming to execute road transportation projects in area or master plan with regards to controlling gully erosion on road transportation systems. Bio-technical control measures requires rainfall data of the runoff catchment area, design and installation of runoff collection ponds at strategic locations on the catchment areas for rural water supply and small scale irrigation purposes, investigation on suitable vegetation for gully bank stabilization in the locality and development of appropriate gully control structures from available local materials. Road construction contractors , consultants and agencies charged with responsibility for maintaining these roads should put into consideration the uniqueness of the areas and the volume of traffic the uses these road at any point in time. REFERENCES Chukwuma, G.O.1985. Bamboo as a Bio-Technical Gully Erosion Control Material. NSAE Annual Conference Paper No 25-012, Owerri. . Chukwuma, G.O. 1991 Rural Water Supply for Domestic And Small-Scale Irrigation. Book of Proceeding on International Conference by the Faculty of Engineering UNN pp.55.62.


Chukwuma, G.O. 1997. Erosion Damages and Control In Agricultural Lands. Proceedings of The First Regional Symposium on Hydrology Of Tropical Watersheds By Nigerian Society Of Agric Engineers At The University Of Nigeria Nsukka. Chukwuma, G.O. And U.G.N. Anazodo.1986. Agricultural Practices in Soil Erosion Control. An Invited Paper Presented of the National Workslop on Soil Erosion at the Federal University Of Technology, Owerri Under The Auspices Of The Federal Ministry of Science and Technology, Lagos. Donahue, R.L.., R.W. Mller and J.C. Shickluna 1977. Sails: Dr Introduction to Soils and Plant Growth. 4th Ed. Prentice-Itall, Inc., Eagle Wood Cliffs, New Jersey 07632. Drummond-Thompson, Phillip. 1990 The Rise of Entrepreneurs in Nigerian Motor Transport from The Journal of Transport History. pp. 46-63. Egboka, B.C.E. 2004. Distress Call and Plea To The Senate Committee For Urgent Actions Against Floods, Soil/Gully Erosion/Landslides Disasters In The Southeast. Paper Presented To Senate Committee On Environment: Roads/Erosion Senate Delegation To The Southeast.p30. Egboka, B.C.E. and E.I. Okpoko 1984. Gully Erosion in the Agulu-Nanka Region Of Anambra State, Nigeria. Proceedings of the Harere Symposium Falola, Toyin and S.A. Olanreqaju, 1986 ed. Transport Systems in Nigeria. Maxwell School of Citizenship and Public Affairs, Syracuse University, Syracuse. Floyd, B. (1965) Soil Erosion and Population Problems in Southeaster Ngeria. The Nigerian Geogr. J. 117, 8(1) 33-44.

Grove, A.T.(1951) Soil Erosion And Population Problems In Southeaster n Nigeria. The Nigerian Geogr. J.117, 291-306. Igbokwe, J.I., Ojiako J.C. and V.C.Nnodu. 2003. Monitoring, Characterization and Controlling of Floodwater Erosion Using Remote Sonsing Techniques. Proceedings of the Technical Session of the 38th Annual General Meeting and Conference of Nigerian Institution of Surveyors, Lokoja. Michael, A.M. and T.P. Ojha. 2003. Principles of Agricultural Engineering Vol. II 3rd Edition Jain Brothers, New Delhi. Oshin, Siji. 1988 Transport Studies In Nigeria: A Review from Odu: A Journal of West African Studies. . pp. 219-225. Oshin, Siji. 1990 Nigerian Railways Under Stress 1912-45: A Study In Colonial Transport Planning And Management from Odu: A Journal of West African Studies. pp49-71. Robinson, Hamlin et. al. 1961 The Economic Coordination of Transport Development In Nigeria. Stanford Research Institute, Menlo Park, CA.. Schwab, G.O., R.K. Frevert, T.W. Edminister and K.K. Barnes. 1981. Soil and Water Conservative Engineering, 3rd Ed. John Wile & Sons New York. Walker, Gilbert James. 1959Traffic and Transport in Nigeria; The Example of an Under Developed Tropical Territory. Her Majestey's Stationary Office, London.

GULLY EROSION THREAT AND NIGERIA ROAD TRANSPORTATION:A CASE STUDY OF SOUTHEASTERN NIGERIA.

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