Geotechnical and Water Quality Assessment of Erosion-Prone Umuagu Village, Ufuma, Southeastern Nigeria

Geotechnical and Water Quality Assessment of Erosion-Prone Umuagu Village, Ufuma, Southeastern Nigeria

^*1Onuchukwu, E. E., ¹Madu, F. M., ¹Ahaneku, C.V., ¹Njoku, A. O., ¹Odinye, A.C. and ²Odesa, G.E.O

¹Department of Geology, Faculty of Physical Sciences, Nnamdi Azikiwe University, Awka

²Department of Geology, Faulty of Sciences, Dennis Osadebey University, Asaba Delta State

^*Corresponding Author

DOI: https://doi.org/10.51584/IJRIAS.2024.907012

Received: 27 May 2024; Revised: 22 June 2024; Accepted: 26 June 2024; Published: 31 July 2024

ABSTRACT

Umuagu village is located in Ufuma town which is one of the sixteen communities in Orumba North Local Government Area of Anambra State. It is located between latitude 6^º 05’N and 7^º 11″E. The developing erosion site which is the subject of this work runs along the Etiti to Obuagu collector road, commencing off the Ekwulobia/Umunze Road and all five gullies found in Umuagu-Ufuma are road-bound, active and disruptive. A total of three (3) soil and three (3) water samples were collected and analysed using standard method. The result of the soil analyses shows that the soil at Uphill Etiti Umuagu contains 88.2% sand, 6.8% silt and 5.0% clay. In the Middle Course Etiti Umuagu, the soil contains 56.4% sand, 18.5% silt and 15.1% clay while in the Down Stream Course Obuagu Umuagu, the soil samples contain 62% sand, 25% silt and 13% clay. From the obtained result, it is apparent that the entire sequence is sandy and loose; a condition that favours easy soil dispersal and erosion. Physical observation of the water samples shows that the water samples are clean, colourless and had no odour. The pH of the water samples was 6.40, 6.5, 6.30 for borehole, river, and stream waters respectively. The total dissolved solids, total hardness and conductivity contents were within the WHO/ FMEnv limits, with concentrations of 002mg/l, 003mg/l and 003mg/l; 48mg/l, 28mg/l and 30mg/l; and 15.60 µs, 14.60 µs and 16.20 µs for the borehole / river/ stream respectively. The values of the heavy metals detected were: Lead 1.690/ 0.9740/ 0.8612; and Chromium 0.020/ 0.00/ 0.00 (these were above the WHO standard except concentration of Lead in the borehole) while there was no trace of Cobalt, Silver, Tin and Aluminium in the water, except for Magnesium and Molybdenum. The concentration of coliform counts was observed to exceed the value of 102 cfu/ml recommended by the World Health Organisation.

INTRODUCTION

Gully erosion and mass wasting are common natural hazards peculiar to many parts of Nigeria. They are natural geologic hazards which arise due to persistent loss of soils. This geologic hazard has been a serious environmental problem in South-eastern Nigeria, causing the degradation of arable lands, destruction of civil engineering infra-structures and underground utilities; silting and pollution of surface water bodies, loss of estates and resident lands. Various researches conducted in this region reported that several factors, such as poor soil engineering properties, inadequate road construction,  poorly  constructed  and  poorly  maintained surface drainage facilities, poor land-use practices and poor vegetation cover, etc., contribute to the continuous soil erosion and the development and expansion of erosion gullies in this part of Nigeria (Emeh and Igwe, 2017, 2018; Igwe, 2012; Igwe and Egbueri, 2018; Nwajide, 2013; Okoyeh et al., 2014).

According to Obidimma and Olorunfemi (2011), the preponderance of gully erosion in Southeastern Nigeria may also be attributed to the inherent geotectonic, geologic, and geo-hydrologic characteristics of the area. Other factors include unplanned sand mining and urbanization, shortened fallow length or continuous cropping, inadequate biomass turnover, cultivation along slopes, numerous (compacted) footpaths, etc. (Osuji et al., 2002; Madueke et al., 2021b). These issues are exacerbated by the very high rainfall amount and intensity in the region necessitating effective land evaluation, land use planning and land allocation. Therefore, the characterization of the nature and properties of soils is a fundamental requirement for sustainable land use planning.

The gully erosion site under study is a subject of the current NEWMAP intervention and it runs along the Etiti to Obuagu collector road, starting from the Ekwulobia/Umunze Road. Although the gullying process commenced upslope, the gully head becomes more prominent at the abrupt drainage termination at the bifurcation to Awulu village, about 65 m from the Federal Polytechnic gate. Umuagu is a rural community with evidence of increasing land use development trailing the siting of the Ufuma Campus of the Federal Polytechnic, Oko which has engendered dense population movement into the village in particular and Ufuma in general. As a consequence, buildings for tenement, renting and shops sprang up at a rapid rate within the project community. Many of the buildings nearest to the access road are undermined or suffer structural damage as a result of the gully erosion. Many are accessed through wooden foot bridges. With the siting of the Ufuma Campus of the Federal Polytechnic, Oko in Umuagu Village, there has been population movement into Umuagu in particular and Ufuma in general. As a consequence, houses and shops of all sorts sprang up on every available space without regard and compliance to development controls and other environmental regulatory frameworks. Many roofed development initiatives are found throughout the sub-watershed, with many premises completely paved. The impervious surfaces harvest and discharge concentrated storm runoff into access road, instigating the gullies and extending it following rainfall events. Many of these buildings and shops are located right on the road shoulders without adequate setbacks. Hence many are undermined and/or destroyed by gully erosion such that they only accessed their compounds through rickety wooden footbridges.

METHODOLOGY

Soil and water samples were collected around the gully site and were analysed for various physicochemical parameters by using standard method. The soil samples were collected at uphill Etiti Umuagu, Middle course Etiti and the Down Stream course to ensure a representative sample. Each sample was taken from top to a depth of 15cm to 15 – 30cm and analysed according to standard method. The samples were packaged in polyethylene bags and taken to laboratory for analyses. Equally, water samples were collected with clean plastic bottles from surface and groundwater sources. The plastic bottles were rinsed with the water before collection of samples. For surface water, the sample bottles were fully submerged before collecting the samples. However, for groundwater, the water is allowed to discharge for about five minutes before collection to ensure freshwater from the aquifer is collected. The sample bottles were covered with the plastic bottle cover. All the samples were appropriately labelled before being taken to the laboratory. The results were compared with WHO standard (2011) and NSDWQ, (2015).

Location of the Study Area

Umuagu in Ufuma Town is one of the villages, is one of the sixteen communities of Orumba North Local Government Area, which has its headquarters at Ajalli. It is located between latitude 6⁰ 03′ and 6⁰ 05’N and 7⁰ 10′ 0” and 7⁰ 12′ 0”E (Fig. 1). It is bounded in the East and West by Inyi and Ndiokpaleke; to the Northwest and southwest, by Omogho and Ndiokpaleze, respectively and in the North by Awa, and shares its Southern boundaries with Ajalli.

Geology of the Study Area

The study area lies in the Niger Delta basin (precisely on the Nanka Formation (Fig. 2)). Outcropping stratigraphic units of the Niger Delta overlying the Anambra Basin are comprised of four lithostratigraphic units: the Imo Formation with an average thickness of ~1000 m; the Ameki Group with thickness that ranges from 1400 to 1900 m; the Ogwashi Formation with estimated thickness of ~250 m and the Benin Formation that is about 2000 m thick at the depocenter (Simpson, 1955; Reyment, 1965; Nwajide, 1980; Arua, 1986; Nwajide,2006; Ekwenye et al., 2015). The Imo Formation forms the basal outcropping stratigraphic unit of the Niger Delta. It widens eastwards, swings southwards, and narrows and tapers off northwest of Odukpani, an area in Calabar Flank, where it is overlapped by the Benin Formation across an age gap of 15 Ma of the Ameki Group and the Ogwashi Formation (Nwajide, 2013). The facies of the Ameki Group conformably overlie the Imo Formation and contains three stratigraphic components: the Ameki Formation, the Nanka Formation and the Nsugbe Formation (Figure 2), which pinch out in both westwards and eastwards (Nwajide, 1980, 2013). The Imo Formation is the mappable equivalents of the Akata Formation and the Ameki Group and Ogwashi Formation are the mappable equivalents of the Agbada Formation of the subsurface stratigraphic units of the Niger delta (Short and Stauble, 1967). The Imo Formation is the oldest stratigraphic unit in the Niger Delta Basin (Short and Stauble, 1967; Petters, 1991) and is composed of blue-grey shales with sand lenses, marl and fossiliferous limestones (Reyment 1965; Short and Stauble, 1967; Nwajide, 2013, Nwajide, and Reijers, 1996). The Ameki Formation is estimated to range from 1200 – 1500 m thick, and comprises mainly of sands, minor silt with thin shelly limestone and calcareous clay intercalations (Reyment, 1965; Arua, 1986; Nwajide, 2013). The Nanka Formation is estimated at 305 m thickness, is mainly sands and minor calcareous clay/mud with heterolith (Nwajide, 1980, 2013; Ekwenye et al., 2014).

Fig. 1: Location map of the study area

Fig. 2: Chrono-Stratigraphic succession of the Cenozoic Niger Delta Basin outcropping in southeastern Nigeria, overlying the Upper Cretaceous Anambra Basin (modified from short and Stauble, 1967; Nwajide, 2013)

RESULTS AND DISCUSSION

Geotechnical and Hydrogeological Analysis: Soil Analysis

The result of the soil analysis is presented in Tables 1a and 1b below;

Table 1a: Result of the soil analysis of the collected samples

Table 1b: Result of the soil analysis of the collected samples (cont.)

The soil at Uphill Etiti Umuagu contains 88.2 % sand, 6.8 % silt and 5.0 % clay. In the Middle Course Etiti Umuagu, the soil contains 56.4 % sand, 18.5 % silt and 15.1 % clay while in the Down Stream Course Obuagu Umuagu, the soil samples contain 62 % sand, 25 % silt and 13 % clay. From the obtained result, it is apparent that the entire sequence is sandy and loose; a condition that favours easy soil dispersal and erosion. This makes the soil easily erodible and this is in agreement with the findings of Abdulfatai, et al., (2014). The concentration of heavy metals such as Iron, mercury, silver, lead, arsenic, nickel and chromium were all found to be above the acceptable limits and this can be attributed to be as a result of the various anthropogenic activities going on in the area.

Water Quality Analysis

The results of the physicochemical and microbiological analysis of the borehole, river and stream, samples are presented in Table 2. Physical observation of the water shows that the water samples were clean, colourless and had no odour. The pH of the water samples was 6.40, 6.5, 6.30 for borehole, river, and stream waters. The total dissolved solids, total hardness and conductivity contents were within the WHO/ FMEnv limits, with concentrations of 002mg/l, 003mg/l & 003mg/l; 48mg/l, 28mg/l & 30mg/l; and 15.60 µs, 14.60 µs & 16.20 µs for the borehole / river/ stream respectively. These findings were observed to be similar with the observation of Madu, et. al., 2022 and Okolo, et. al., 2023.

The background concentrations of heavy metals in the Borehole, River, Stream were analysed. The values of the heavy metals detected were: Lead 1.690/ 0.9740/ 0.8612; and Chromium 0.020/ 0.00/ 0.00 (these are above the WHO standard except concentration of Lead in the borehole) while there was no trace of heavy metals such as Cobalt, Silver, Tin and Aluminium in the water, except for Magnesium and Molybdenum. The concentration of coliform counts was observed to exceed the value of 10² cfu/ml recommended by the World Health Organisation and this indicates that the water is unfit for consumption (Madu, et. al., 2022).

Table 2: Water Analysis result

CONCLUSION

The study of Umuagu village in Ufuma town, located in Orumba North Local Government Area of Anambra State, has highlighted significant environmental concerns, particularly related to soil erosion and water quality. The soil analysis revealed a predominance of sandy and loose soil compositions throughout the erosion sites at Uphill Etiti, Middle Course Etiti, and Down Stream Course Obuagu. This sandy texture, which comprises up to 88.2% sand in some areas, contributes to the susceptibility of the soil to erosion, leading to the formation of active and disruptive gullies along the Etiti to Obuagu collector road.

Water quality analysis indicated that, although the physical characteristics of the water samples appeared satisfactory, the chemical analysis raised several red flags. While the pH levels, total dissolved solids, total hardness, and conductivity of the water samples fell within the permissible limits set by WHO and FMEnv, the concentrations of heavy metals, particularly lead and chromium, were concerning. The lead levels in the water samples exceeded WHO standards, posing potential health risks. Moreover, the presence of coliform bacteria at levels surpassing WHO recommendations further underscores the need for urgent intervention to safeguard public health.

In summary, the findings from this research underscore the critical need for comprehensive soil and water management strategies in Umuagu village. Mitigating the erosion problem will require soil stabilisation efforts, and addressing the water quality issues will necessitate measures to reduce heavy metal contamination and microbial pollution.

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