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Background of the Study
Erosion is the action of exogenic processes (such as water flow or wind) which remove soil and rock from one location on the earth’s crust and transport it to another location where it is deposited . It is equally a natural process by which the surface of the earth gets ice. But anyone who has ever seen a picture of the Grand carryon knows that nothing beats the slow steady movement of the water when it comes to changing the earth (Blanco and Lal, 2010). Excessive (or accelerated) erosion causes both ‘on site’ and ‘off site’ problems. On site impacts include decrease in agricultural productivity and (on natural landscapes) ecological collapse, both because of loss of the nutrient-rich upper soil layer. In some cases, the end result is desertification. Off-site effects include sedimentation of water ways and entrophication of water bodies as well as sediment-related damage to roads and houses. Water and wind erosions are the two causes of land degradation when combined; they are responsible for about 84% of the global extent of degraded land, making excessive erosion one of the significant environmental problems world-wide (Toy and Terrance, 2002). Generally, gullies are formed by an increase in surface run-off.
Therefore minimizing surface run-off is essential in gully control. Water sheds deteriorate because of man’s misuse of the land, short intensive rainstorms, prolonged rains and moderate intensity and rapid snow melts. These precipitation factors also turn into high run-off which causes flooding and forms gullies (Blanco and lal, 2010).
Gullies erosion is the removal of soil along drainage lines by surface water run-off. Once started gullies will continue to move by head ward erosion or slumping of the side walls unless steps are taken to stabilize the disturbance. Gully erosion occurs when run-off water accumulates and rapidly flows in narrow channels or immediately after heavy rains or melting snow removing soil to a considerable depth (Christensen, 2003). A gully is a landform created by running water, eroding sharply into soil, typically on a hillside. Gullies resemble large ditches or small valleys but are meters to tens of meters in-depth and width (Costard et al, 2009).when the gully formation is a process, the water flow rate can be substantial which causes the significant deep cutting action into soil (Poesen and Jean, 2002). A gully may grow in length by means of head ward (i.e. upstream) erosion at a knick point. This erosion can result from interflow as well as surface runoff. Gullies reduce the productivity of farmland where they cut in into the land and produce sediment that may clog downstream water bodies. Because of this, much effort is invested into the study of gullies within the scope of geomorphology, in the prevention of gullies landscapes. The total soil loss from gully formation and subsequent downstream river sedimentation can be sizeable. Gullies are formed where many hills join and gains more than 30cm depth. The rate of gully erosion depends on the run-off producing characteristics of the watersheds: the drainage area; soil characteristics, the alignment, size and shape of the gully and the gradient of the gully channel. Gullies are very destructive and cannot be eliminated by telling or ploughing because of their depth (Albert et al 2009). However, a lot of measures have been embarked upon to reduce the impact of gully erosion in many communities in Nigeria.
In Uli community in Ihiala Local Government Area of Anambra State, the history of erosion disaster is dated back to the 1930’s when gully sites were first observed (Onwuka and Okoye, 2009). As of today, about nine villages in Ihiala Community are affected with one form of erosion or the other, Uli community which is one of the major communities in Uli Local Government area is now known as one of the major erosion prone areas in South-East Nigeria and the causes of the gully have been traced to the fragile geological for formation and soil type of the area, which only requires the top soil to be removed for gully to begin (Egboka 1995). The social and anthropological impact of gully erosion in Uli in Ihiala Local Government Area can be great and sometimes grave as it may affect the soil resources and may significantly alter productivity and life sustenance of the area especially its rural settlement which promotes subsistence farming as the major occupation of the people.
1.2 Statement of the problem
The more pressure continues to exert on the land due to increase in population and topography of the area, the more gullies continue to spread. However, several efforts of the community in trying to contend the situation have proved abortive, thereby rendering the area useless to agriculture, affecting many socio-economic and physical activities in the affected environment, as well as destruction and check of lands for various uses (Egboka 1995).
Moreover, the intervention of the colonial officers during 1940’s through construction of dams and vegetation planting went a long way in slowing down the rate of development of the gully’s and recently, modern erosion control measures are being put in place while some are well coordinated and are effective. Others are discovered to be exerbating the disasters. The colonial officers also introduced the means of checking flood speed by digging sumps and tree planting.
These also helped at that time to check the spread of the gully erosion but unfortunately the government failed to deploy maintenance workers permanently on sites as advised by the colonial officers thereby creating a situation that worsened the gully erosion condition in Uli Ihiala Local Government Area of Anambra State (Igboka 2007). However, the researcher wonders if these could have a great impact on the livelihood of the people of the area. Hence the researcher sought to find out the impact of gully erosion in Uli Ihiala L. G. A. of Anambra State.
1.3 Aim and Objectives of the study
The aim of this study is to determine the impact of gully erosion in Uli, Ihiala L. G. A. of Anambra State. Specifically, the study sought to:
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