Reclamation Measures for Gully Erosion Site. A Case Study of Obollo-etiti Udenu Local Government Area, Enugu State
Objectives of the Study
- To determine the cause of the gully erosion in the Obollo-Etiti, Udenu L.G.A. gully site.
- To construct maintain and unrest in the study are unfrustural works like roads, water schemes and gradual transfer of these to benefiting communities to engage in other activities that will increase agricultural production in the soil.
- To design appropriate soil erosion control structures for gully erosion site.
REVIEW OF RELATED LITERATURE
Soil erosion is a common term used to either mean soil degradation or the physical removal of soil. Soil erosion is the detachment and transportation of soil particles by agents such as wind or water (Toy et al. 2002). This term can apply easily to gullies because soil is removed and is usually caused by some sort of soil degradation. However, most classify the type of erosion by the erosive agent, wind or water, which causes the erosion. Water erosion can be caused by rainfall, surface runoff from rainfall, and surface runoff from irrigation. Runoff occurs once the precipitation rate exceeds the infiltration rate of the soil. As precipitation continues to exceed infiltration, water begins to move down slope as overland flow or in defined channels (Ward and Stanley W. Trimble 2004). The detached soil particles that result from runoff and erosion are deposited in receiving water bodies, which has led to a higher impairment of water quality. Erosion is more likely to take place on lighter textured soils and on slopes rather than in valley floors (Boardman and Favis-Mortlock 1998). Soils containing more fine sand are more likely to give way and erode, which results in sedimentation (Dvořák and Novák 1994). Sedimentation is a major problem causing pollution in streams and rivers. Sediment does not only carry soil particles but also carries nutrients that are found in the soil such as large amounts of phosphorous. These excess nutrients can cause overgrowth of algae, leading to the depletion of oxygen and ecosystem disruption (USEPA 2007a). Sedimentation caused by erosion can alter aquatic habitat, suffocate fish eggs and bottom-dwelling organisms, and impair drinking water treatment processes and recreational use (USEPA 2007a). Erosion and nonpoint source pollution are interrelated. As erosion increases, so does nonpoint source pollution while water quality decreases. Therefore, if erosion can be controlled, nonpoint source pollution can be minimized and water quality can be improved. This can be done by gaining a better understanding of the causes of and processes involved in the formation of erosion.
MATERIALS AND METHODS
Traverse method of survey was employed to gain access to sample locations. Soil samples were obtained from incipient gullies at depths of 0.5m and 3.0m, wrapped in polythene bags and taken to the laboratory for Atterberg limits determination. In addition, particle size analysis for the soil samples was carried out using the American type of standard sieve (Half-phi ASTM Stand) and a digital weighing balance. Furthermore, compaction test was done with the aid of a BS1377 mould and a 2.5 hammer.
Geology of the study area
Study area: The study area is Udenu local Government Area of Enugu State, Nigeria. Obollo-Afor is the administrative headquarter of the Local Government Area. The study area lies approximately at latitudes 6°481N and 6°581N and Longitudes 7°261E and 7°401E. It covers an area of 248 km2.
Causes of gully erosion in Obollo-Etiti Udenu Local Government Area, Enugu State:
Some of the most likely causes of gully erosion in Obollo-Etiti Udenu Local Government Area, Enugu Stateare:
The liquid and plastic limits were used to obtain the plasticity index which is a measure of the plasticity of the soils Onwemesi (1990). A plasticity chart was plotted. From the plasticity chart (table 1), all the soil samples from the various gully sites have their plots clustered within the low plastic range (Figure 3), hence they are cohensionless. The values of the plastic index obtained ranged from 1.2% to 5.2% which is very low. Therefore the noncohesive or the friable nature of the soils in the area account for the gully erosion problems because water flows through the soil with ease and move the soil particles down slope with increase in velocity of motion of the water.
The causes and impacts of gully erosion in obollo-etiti had been investigated using various techniques highlighted in this work and others from previous works on gully erosion in obollo-etiti. It was observed that both anthropogenic and the human-induced factors were responsible for the phenomenal, which has resulted in devastating impacts on the residents, property and their environment. Field observations by this study had shown that local geology, run-off as encouraged by most residents of community in the affected areas, nature of the soil porosity and loose sands, as well as the condition of groundwater at the sites were prominent contributors to the rates and magnitude of gullying in parts of obollo-etiti community. By way of proffering tangible measures that would help in no small measures in tackling the menace of gully erosion in obollo-etiti community, Governments at all levels should collaborate to find a lasting solution to the phenomenal by adopting recommendations contained in this study as well as integrating other ones not mentioned here but would complement the efforts of an holistic tackling of the menace.
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