Effectiveness of New Map Water Retention Techniques on Erosion Control in Garden Street and the Adjoining Areas of Calabar South LGA, Cross River
Chapter One
Study Objectives
In addressing the research questions in the Calabar South, the objectives were to determine:
- Factors that cause soil erosion.
- Geomorphologic landforms resulting from soil erosion.
- The impact of soil erosion on crop production, especially maize.
- New map water retention techniques used in Calabar South to control soil erosion.
CHAPTER TWO
LITERATURE REVIEW
Introduction
The objective of this review was to highlight some important scientific works that are available on Soil erosion and its impact in the World, Africa, Nigeria, Cross River, and Calabar sub-location. This was deemed necessary in revealing trends in research activities on causes of soil erosion, its impact on landforms and crop yields and new map water retention techniques, which were considered useful to this study. The review was also meant to reveal new map water retention techniques. The review is organised into topical issues based on the study problems, objectives and hypotheses.
Soil Erosion
Soil erosion is a naturally occurring process that affects all landforms, by the natural physical forces of water and wind. Soil erosion can be a slow process that continues relatively unnoticed or can occur at an alarming rate, causing serious loss of topsoil. It involves three distinct actions; soil detachment, movement and deposition. A great deal of research work has been done over the years on soil erosion and its impact on the earth surface. The problem is more pronounced in the marginal lands due to cultivation and overgrazing (Denga et al; 2000). Denga et al; (2000) citing the UNEP report (1987) noted that the problem of soil erosion as had a long history in Nigeria, where by 1935 it had become a major environmental problem, increasing in the 1960s when the nature of approach to soil conservation changed from enforcement to advisory, which led to a temporary breakdown of soil conservation activities but this changed in the 1970s when attention focused on land management and conservation practices, with a view to reducing the problem of soil erosion.
Erosion problem in Nigeria has mainly been considered in terms of water movements as shown in the work of Dunne et al; (1976), Dunne et al; (1978), Ongwenyi (1978, 1979), Edwards (1979) and Waine (1983) where the focus was on erosion by water with a general conclusion that soil erosion rates in Nigeria were increasing leading to surface degradation, which they considered as an environmental problem. Stockdale (1937), Sutherland (1990), Thomas et al; (1997) all indicated that soil erosion in Nigeria was one of the most serious land problems. The present study was focused on soil erosion problem in the Calabar South in Central Division of Cross River, Nigeria.
Factors Influencing Soil Erosion
Several studies have examined various factors that influence soil erosion. Wischmeier et al; (1965) examined factors that influence soil erosion within a catchment. They developed a model referred to as Universal Soil loss Equation which is important in evaluating the problem of soil erosion within a catchment. Margareta (1982) working on soil erosion by water in different climates found that the major factors which affect soil erosion were climate, relief, soil and vegetation. Kitheka (2000) found important factors accelerating soil erosion to be slope or gradient, ground cover, soil/rock type, land use and climatic factors. Mbuvi et al; (2000) found climate, relief, soil erodibility, land use and surface cover to be the main factors considered for erosion susceptibility. This study used Margareta`s classification and grouped factors influencing soil erosion into three categories of physical, geological and human activities.
Physical Factors
Physical factors include rainfall, wind, and vegetation cover. Rainfall is the amount and intensity of precipitation, seasonality, and storm frequency in an area. Rainfall intensity generally refers to the amount of rainfall that is recorded within a given period of time. Rainfall amount is an important factor in causing soil erosion in a catchment. The importance of rainfall amount in causing soil erosion is in connection with storm duration and intensity. Several studies have attempted to define the most erodible climatic environments in terms of annual sediment output from catchments of varying sizes, (Langbein et al; 1958; Wilson 1973; Walling et al; 1979). The above studies found complex interrelationship between sediment yields and climatic characteristics. Langbein et al; (1958) related sediment yields to annual precipitation within a range of climatic zones. Their study found that, high rainfall leads to high runoff in arid regions which causes increased rates of soil erosion. Douglas (1967) in his study also related sediment yields to annual runoff.
Roose (1967) regard the maximum rainfall intensity greater than 60mm/hr for 15 minutes, as an important parameter in causing soil erosion. The study established that the most effective rainfall intensity in causing soil erosion in the catchment was in the range of 45 mm/hr and 77 mm/hr. Wilson (1973) in his review of previous investigations concluded that variations in climatic regimes and land use characteristics make it difficult to come up with a single rule relating sediment yields to rainfall or runoff for a relatively small area. Christianson (1981) assessed the problem of soil erosion in semi- arid Tanzania and analyzed climate, soil type and slope as factors of importance for the initiation and acceleration of soil erosion. The study also discussed the geomorphologic effects of erosion processes in the semi-arid environments. According to Hudson (1981) only storms with mean rainfall intensity greater than 25 mm/hr are effective in causing soil erosion.
Imeson (1983) studied soil erosion thresholds in semi-arid areas in Northern Morocco. The approach adopted was the use of field measurements, to determine rates of erosion and infiltration. The study found that other factors need to be considered if the erratic response of erosion to rainfall in semi-arid areas is to be explained. It was established that potential for erosion reflected in the high erodibility of the soil and low infiltration rates does not necessarily result in high rates of runoff and soil erosion. The difference in soil loss was found to be explained by differences in soil conditions. Investigations by Brandt (1990) in river systems in Sweden have shown that erosion loses from experimental index plots could not be easily extrapolated to large areas. Brandt found that the transportation of sediments in rivers of Sweden to be highly correlated to runoff.
In Nigeria several studies have been carried out on the relationship between rainfall and soil erosion in different areas. Quoting the works of Wischmeier et al; (1962) and Hudson (1971), Othieno et al; (1977) found that little erosion occurred when the rainfall intensity is less than 20 mm/hr in Kericho, Nigeria. Ongwenyi (1978) and Nyandega (2008) found that rainfall factor was an important variable in soil erosion processes in the upper Tana catchment. Suthern et al; (1990) in their work, established that, suspended sediment yield was high with main sources being fine grained colluviums and a significant relationship between rainfall volume and eroded sediment load for kotiorin catchment in Baringo. Kitheka (1994), citing the work of Dunne (1976) on soil erosion in Kajiado County, found that rainfall amount and intensity is an importation factor in causing soil erosion, especially on bare ground, where rain drops hits the soil with great kinetic energy causing splash erosion and compaction of the upper horizon of the soil, leading to greater erosive power. According to USDA (2001) water erosion is caused by the impact of raindrops on bare soil and by the power of running water on the soil surface. The amount of run-off can be increased if infiltration is reduced due to soil compaction, Ritter (2024). The study also established that, if the rainfall generally comes when fields are being prepared there is a much higher likelihood for soil erosion to occur and special care should be taken to protect these fields. Run-off concentrated by poorly designed or maintained roads or trails can cause accelerated erosion on the adjacent slopes and roadbeds.
CHAPTER THREE
RESEARCH METHODOLOGY
Introduction
This study used multistage sampling procedure to acquire the necessary data where the surface area was first covered by transects. Each transect was treated as a stratum. From each transect the erosion surfaces, various land uses were treated as clusters since erosion landforms and land uses are expected not to have continuous coverage in the catchment.
Data Types and Sources
This study used both primary and secondary data to address the stated problems and meet the study objectives. Primary data was collected directly from the field on erosion occurrence, resulting landforms, topography, land cover and land use, erosion impacts on crop production and new map water retention techniques. The primary data was sourced from the field through observations, measurements and interviews. Terrain data was obtained through measurements using GPS receivers. Data on vegetation cover was obtained through observation and interviews as was the case with human activities. The data on landforms resulting from soil erosion in Calabar South was based on inventory of landforms developed during reconnaissance. Additional data was collected through measurements and observation of landforms and by interviewing the residents.
The data on new map water retention techniques measures to control soil erosion was obtained from both residents and government of Nigeria officials. The data were for terraces, planted trees and application of manure in the farms by farmers to mitigate soil erosion and enhancing new map water retention techniques. The official data was on what the Government and Non-Governmental Organizations were doing to help the residents control soil erosion such as gabion construction and extension services and training. The data on new map water retention techniques was obtained through interviewing the residents as well as soil conservation officers and field observation. The collected data provided information thought to be adequate in assessing the extent and impact of new map water retention techniques being carried out in Calabar South.
The secondary data were mainly on geological and environmental data including geology, agro-ecological zones, relief and soils, rainfall, and land use, and socio- economic data including population. Secondary data was sourced from government databases, topographical maps and Remote sensed data based on Radar measurements (The Nigeria terrain data 2024), scholarly publications, journals, and statistical abstracts. Rainfall data was obtained from meteorological department of Nigeria for stations in Cross River. Soil type data was obtained from Nigeria Agricultural Research Institute (KARI) and from existing soil maps. The data collected has helped to determine factors that cause soil erosion in Calabar South.
CHAPTER FOUR
RESULTS AND DISCUSSIONS
Introduction
This study addressed the causes of soil erosion in Calabar South, geomorphologic landforms due to soil erosion in Calabar South, impacts of soil erosion on crop production especially maize in Calabar South, and new map water retention techniques being used in Calabar South to control soil erosion.
Of all the 44 respondents, 59.1% were males and 40.9% were female giving none bias gender representation. This is because males and female have different roles in the Calabar South which may affect soil erosion in one way or the other. However in many homesteads the males were likely to be the heads of households and responded to the questionnaires. The two groups were then grouped further into 5(five) groups based on age; 20-24, 35-39, 40-44, 50-54, 55-59 and 60-64 years. The respondents were also grouped according to the occupation of various knowledge, and residency.
CHAPTER FIVE
SUMMARY, CONCLUSIONS AND RECOMMENDATIONS
Summary and conclusions
From the study findings it was concluded that soil erosion is a serious problem in Calabar South. The summary of the findings were done according to the specific findings obtained in chapter five. The study found out that the factors causing soil erosion in Calabar South in Cross River to be human activities, such as overgrazing, deforestation, Poor farming methods especially along the river bank and on steep slopes, lack of new map water retention techniques, excavation of the steep slopes, Sand harvesting, brick making, the above factors are aggravated by population increase. The study found out the physical factors contributing to soil erosion in the Calabar South are soil type, steep slopes, seasonal rains and prolonged dry period.
The study sought to find out the main types of landforms in Calabar South formed as a result of soil erosion. The landforms were tree mounds, caves, residual hills, rills and gullies. Wide and deep gullies were found to interfere with human activities such as cultivation and movement of people and animals.
The study also sought to find out the impact of soil erosion on crop production especially maize in Calabar South. Crop yields are low in areas severely affected by soil erosion, the areas with thin top soils and areas with many geomorphologic landforms. The farmers in the area are aware that soil erosion in the catchment was caused by both human and physical factors. The chiefs reports show that the local government sends out warnings to the residents indicating that the zone is prone area to soil erosion and therefore people should conserve soil in their farms. Additionally, the local government discourages settlements on steep slopes and carrying out activities such as charcoal burning and sand harvesting, because they would accelerate soil erosion in the area. Soil erosion occurrence in Calabar sub- Location in Cross River is not related to single factor within the catchment but a combination of human, geological as well as environmental factors.
The main factors which cause soil erosion are human activities such as deforestation, overgrazing, charcoal burning, brick making, sand harvesting, excavation of the slope through road cuts, establishment of settlements on steep slopes, cultivation along the river banks and increased agricultural activities. The study also concluded that physical factors such as low and seasonal rainfall, sparse vegetation cover, shallow sandy soil and steep slope significantly contributed to the occurrence of soil erosion in Calabar sub-location.
Further, it was concluded that soil erosion in Calabar has formed geomorphologic landforms which have adversely affected physical and social-economic environment through land degradation, destruction of infrastructure, and displacement of residents, siltation of rivers and reduced maize yields. The soil erosion new map water retention techniques in the area were established to be many and generally in the form of terraces, planted trees, gabions along gullies and weirs across the river channel to reduce the speed of water and rate of soil erosion. The majority members of the community were aware of the new map water retention techniques necessary to control soil erosion in the Calabar South.
Recommendations
Policy Recommendations
The study makes the following recommendations:
Policy makers should ensure that education campaign on soil erosion is embraced by the residents of Calabar sub-location to restore soil erosion in the catchment.
The County government should ensure that appropriate extension services for restoration of eroded areas and improving land productivity through increasing budgetary allocation of Calabar sub- sub-location.
The County government should take severe measures against destruction vegetation cover by having penalties that are answerable to the law.
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