Morphometric and Morphological Analysis of Gullies in Lafia Lga, Nasarawa State, Nigeria

Table of contents

1. Introduction

ully erosion is the removal of soil along drainage lines by surface water run-off. According to the Department of Primary Industries and Water -Tasmania, Australia (2008), gully erosion is known to be the most destructive form of soil erosion in Nigeria, which is caused by heavy or sudden rain storms which produce concentrated run-off enlarging rills into cheap channels, the run-off cuts deep gushes or gullies of over 10 meters to 20 meters and in severe situations reaching up to or over 100 meters into the land. It occurs more generally where land slopes are steep and surface run-off is exceptionally heavy. Once started, gullies will continue to move by head ward erosion or by slumping or collapsing of the side walls changing it from V-shape to U-shape valleys (Abengude et al., 1991). The United States Department of Agriculture (2006) also regards gullies as channels formed by the concentrated flow of water, removing upland soil and parent material and of size too large to be obliterated by normal tillage operations (USDA, 2006).

Rills are initial stage in channel erosion which undergoes systematic transformation into gullies. Rill erosion is defined as erosion in numerous small channels that are uniformly distributed across a slope and can be obliterated by tillage (Hutchinson & Pritchard, 2002). In these and several other areas, gully erosion is a serious threat to economic development of the localities involved. Gullies are relentless destroyers of arable land. They cut up fields, agricultural lands and sometimes-entire village into small, odd-shaped parcels and restrict the free movement of farmers and animals. They are a menace to livestock as animal frequency fall in and are unable to escape. Gullies also threaten village roads, buildings and other structures. In AkwaIbom State, for instance gullies have claimed two lives and several buildings in Obotme area (Udosen, 1991), more than 20 houses and a stadium complex have been destroyed by a 1km long gully system that was initiated along Eka Street in Uyo area (Armon, 1984). Currently, gullies are eroding deeply into the major Onitsha-Owerri Road near Onitsha.

According to Fubara (1988), about 16,668km 2 or 22.8 percent of the total land surface in eastern Nigeria is affected by severe forms of gully erosion. Available records also show that in all the south eastern states except the former Rivers State, about 25,000 hectares of land are lost annually to fluvial erosion, especially by gullying. In addition, the topsoil which contains significant proportion of soil nutrient and organic matter are being washed away at alarming rates by the invidious process of sheet erosion. As the stabilization of gullies is the most expensive of all erosion control works as the checking and elimination of gullies often requires. Extensive earth moving and construction of dams and/or other measures, it is vital to prevent gullies from developing and this can be done through the identification of critical factors for gully initiation and sometimes general lack of information on drainage basin parameters is a failure that has contributed to the significant lack of success in solving erosion parameters in the region.

In view of the foregoing, a question which arises is what are the actual environmental factors responsible for gully initiation and sustenance in the study area? Erosional factors are simply the critical condition or a combination of factors at which soil erosion is initiated. It may be induced when an internal or an intrinsic threshold or an external or extrinsic threshold is exceeded e.g., through changes in climate or land use. It is generally known that the pattern of soil erosion changes as the vegetation cover and other factors are altered. Thus, in a given landscape whether a gully is initiated or not depends on the nature of the earth material, the extent of the vegetal cover, and the slope length and gradient all of which combine to determine, the resistance to the attractive force of fluvial processes.

During the 17 th and 18 th centuries, Easter Island experienced severe erosion due to deforestation and unsustainable agricultural practices. The resulting loss of topsoil ultimately led to ecological collapse, causing mass starvation and the complete disintegration of the Easter Island civilization (Rattan et al., 2010). Due to the severity of its ecological effects, and the scale on which it is occurring, erosion constitutes one of the most significant global environmental problems we are facing today. Water and wind erosion are now the two primary causes of land degradation combined; they are responsible for 84% of degraded acreage. Each year, about 75 billion tons of soil is eroded from the land -a rate that is about 13 -40 times as fast as the natural rate of erosion. Approximately 40% of the world's agricultural land is seriously degraded (Morgan, 2015). According to the United Nations (2004), an area of fertile soil the size of Ukraine is lost every year because of drought, deforestation and climate change. In Africa, if current trends of soil degradation continue the continent might be able to feed just 25% of its population by 2025, according to UNU's Ghana -based institute for Natural Resources in Africa.

The loss of soil fertility due to erosion is further problematic because the response is often to apply chemical fertilizers, which lead to further water and soil pollution, rather than to allow the land to regenerate. Soil erosion (especially from agricultural activity) is considered to be the leading global cause of diffuse water pollution due to the effects of the excess sediments flowing into the world's waterways. The sediments themselves act as pollutants, as well as being carries for pollutants, such as attached pesticide molecules or heavy metals. The effect of increased sediments load on aquatic ecosystems can be catastrophic. Silt can smother the spawning beds of fish, by filling in the space between gravel on the stream bed. It also reduces their food supply, and causes major respiratory issues for them as sediments enter their gills. The biodiversity of aquatic plant and algal life is reduced, and invertebrates are also unable to survive and reproduce. While the sedimentation event itself might be relatively short-lived, the ecological disruption caused by mass die off of aquatic plant often persists long into the future.

One of the most serious and long-running water erosion problems worldwide is in the People's Republic of China, on the middle reaches of the Yellow River and the upper reaches of the Yangtze River. From the Yellow River, over 1.6 billion tons of sediment flows into the ocean each year. The sediment originates primarily from water erosion in the Loess Plateau region of the northwest (Abaje, 2007). Soil particles picked up during wind erosion are a major source of air pollution, in the form of airborne particulates "dust". These airborne soil particles are often contaminated with toxic chemicals such as pesticides or petroleum fuels, posing ecological and public health hazards when they later land, or the inhaled and/or ingested (Faniran, 1978). Dust from erosion acts to suppress rainfall and changes the sky colour from blue to white which lead to an increase in red sunsets. Over 50% of the African dust that reaches the United States affects Florida. Dust events have been linked to a decline in the health of coral reefs across the Caribbean and Florida, primarily since the 1970s. Similar dust plums originate in the Gobi Desert, which combined with pollutants, spread large distances eastward, into North America (Abaje, 2007). The removal by erosion of large amount of rock from a particular region, and its deposition elsewhere, can result in a lightening of the load and mantle, causing tectonic or isotactic uplift in the region (Giles, 2011). The apparent advance of land degradation and frequent erosion occurrence in middle belt region of the country during the last 12 decades have brought about a whole series of environmental, ecological and socio-economic problems.

In Nasarawa State, a vast area of farmlands has been lost due to the menace of gully erosion while others are at their various stages of destruction leading to drastic decrease in agricultural productivity and ultimately food shortage that can lead to famine (Anzaku, 2015). The gully erosion in the state has resulted in loss of vegetation as its continuous expansion encroaches into areas that are forest leading to falling of trees and exposure of more surface area to gully activities. Several properties such as building structures whose value cannot be quantified accurately Volume XXI Issue III Version I 90 ( ) have been destroyed. Besides, it was reported recently that several buildings were lost in Nasarawa State of Nigeria as a result of erosion (NBS News, 2014). Many lives have been lost as a result of the problem of gully erosion in the state NBS, (2012). Some either fell into these gullies or sustained various degree of injury. About 7 people have been reported in the past few years to have lost their lives as a result of flooding that drown them to gullies (NBS, 2012). Gully erosion therefore has resulted in the separation of adjacent villages and towns as it may involve collapse of bridges linking them together. This has had negative impacts on such areas since some facilities such as schools, hospitals and water supplies shared by the affected neighbouring communities may become inaccessible. Transportation of farm produce has also been affected and this also often leads to loss of agricultural products especially, the perishable ones. Area in Plateau State to the east. Lafia's location at the junction of a regional road confers on its good linkage with Makurdi, Benue state to its south, Akwanga-Keffi and Abuja to its north-west and Jos, Plateau state its north-east.

2. b) Sample and Sampling Technique

Twelve (12) gully sites were purposively selected from Lafia. The sampling technique that was adopted by the researcher was the non-probability (purposive) sampling technique.

3. c) Types and Sources of Data

Both primary and secondary sources of data were employed in this study.

4. d) Identification and Characterisation of Gullies in the Study Area

Field survey, measurement, and observation was carried out. More so, soil samples of each sampled gully sites were collection and subjected to laboratory analysis, to determine the particle size of each of the sampled gully sites in the study area. GPS device was also used to get the coordinates of each identified gully in the study area. The rationale for adopting these methods was premised on the recommendations of Young (1999).

5. e) Determination of the Volume of Soil Loss in the Study

Area Revised University Soil Loss Equation (RUSLE) model was used for the quantification of soil loss. This Volume XXI Issue III Version I

6. f) Determination of Gully Morphometry in the Study

Area A 30m linen tape, ranging poles, Abney level and pegs in measuring the length, width, depths and area at carefully selected points, usually at regularly space intervals of between 0.5m and 20m depending on the length of the gully in each of the sampled area of the study. A was stretched taut across it to determine the top width. Gully depth were measure from the tape of the gully bed (with another tape). The depth was measured from the gully floor to the top string using a ranging pole (graduated in meters). An Abney level was used to measure the slope angle. The length of the slope from the crest to the base from the side was measured with a 30m tape wand expressed in meters. The average value for each sampling area was also computed. This method was adopted by the researcher, in line with Mbaya, et al.

7. g) Determination of Gully Morphology in the Study Area

Field observation method was adopted in determining the gullies morphology parameters. These include the class of gullies in the study area, their shapes, and stages of development, shape factor and direction of flow, is in line with the studies of Leopol and Miller (1956), Heede (1975), Bocco (1990Bocco ( ,1991)), Ireland et al. (1996), and Cudoson, (2005).

8. h) Gullies Mapping

GPS coordinates of gullies identified during the field survey were collected and used for mapping of areas affected by gully erosion in the study area. ArcGIS and ENVIS software were used for mapping at Nasarawa Geographic Information System (NAGIS). This method was adopted in line with the works of Mbaya et al.

9. i) Method of Data Analysis

Both qualitative and quantitative methods of data analysis were adopted. Qualitative method of data analysis was used to explained and interpret the results of the study, with respect to data extracted from field work, map analysis, and laboratory soil particle size, while the quantitative method of analysis was adopted to analysed quantitative data collected from the field. The quantitative methods of analysis adopted with both descriptive and inferential methods or statistics. Descriptive statistics such as range, mean, standard deviation, variance, simple percentages, and coefficient of variation were used to determine the variability of gullies morphometric properties and the variability of rainfall in the study area, and soil particle size, while the inferential used in the study was the correlation analysis, employed to assess the correlation between the length, depth, area and width of gullies in the study area. specifically, the Pearson Product Moment Correlation was adopted. More so, the significance of the correlation between the length, depth, area and width of gullies in the study area was tested IBM SPSS software package (version 26). These methods of data analysis were adopted by the researcher in line with the works of Mbaya et al.

10. III.

11. Results and Discussion

12. a) Characterisation of Gullies in the Study Area

It is important to note that the morphological expression of gullies depends on the landscape unit, stages of development of the gullies, the characteristics of the soil profile, the slope position on which they develop and the dominant processes of the gully deepening and widening. Two criteria are generally employed in the classification of gully system; topographic location in relation to an established drainage system, and the nature of the material in which they are formed (Brice, 1966, Ebisemiju, 1979). Brice (1966) argued that the depth of a gully, its real pattern and its growth are more closely related to the topographic position of the gully head than any other single factor. Generally, incipient gullies in the study area have deep and narrow channels with sharp pointed Volume XXI Issue III Version I 92 ( ) head scarp, while mature gullies are deep, wide and are characterised by broadly-lobed heads.

The data presented in Table 1, and 2, were obtained from Lafia Local Government Area of Nasarawa State. Table 1 depicts the general characteristics of gullies in the study area, such as the length of gullies, the area of gullies, the width of gullies, and the depth of gullies. The table also show the various cross sections of gullies in the study area, as well as particle sizes such as sand, silt, and clay. Table 2 on the other hand depicts the geographical coordinates of gully sites, as well as the magnitudes of gullies in the study area. From the results presented in these tables as well as photographs taken from the various gully sites visited, it is important to point out that gullies in the study areas are characterised by streams, dense vegetation, and terrain-steep slopes. From the data presented in the Table 1 and Table 2, it was observed that gullies in the study area are characterised with either U-shape, V-shape or V and U-shape cross sections. Similarly, the data present in both tables shows that the magnitude of gullies found in the study area are either small, very small, medium or large gullies. Hence, the peculiar characteristics of the sampled twelve gully sites in the study area gives a true picture of the general characteristics of gully system in the study area. More so, the mean length of gullies in the study area was 183.25m (meters), with a coefficient of variation of 0.01m, while the average area covered by gully erosion was 2331.07m 2 (meters square), with a relative variability of 0.04m 2 . Similarly, the mean width of gullies in the study area was 10.59m, with a relative variability of 208.86m, while the mean depth of gullies in the study area was 6.08m, with a relative variability of 0.79m. With respect the soil particles sizes in the study area, the results depicted in Table 1, shows that the mean size of sand in the study area was 88.9%, with a relative variability of 0.03%, while the mean size of silt was 3.98%, with a relative variability of 0.25%. Similarly, the mean size of clay in gully sites in the study area was 7.48% with a relative variability of 0.37%. In terms of the cross-section of gullies, majority of gullies in the study area were U-shaped gullies. Explicitly, a total of 8 gullies in the study area were U-shaped gullies. The results (Table 2) also revealed the presence of V-shaped gullies, as well as U-V-shaped gullies in the study area. This discovery is in line of Udosen (1999).

The results presented in Table 2 revealed the magnitudes of gullies in the study area. From the results, it can be observed that from the entire gully sites covered in the study area, a total of 6 large gullies were recorded in Lafia Local Government. These gullies were found in Adogi, Akurba, Kilema, Tudun-Allu, Ungwa Shawu, and Ungwa Tiv respectively. The large gully found in Akurba recorded a gully length of 285m, width of 17.3m, gully depth of 12m, and covering an area of 4930.5m 2 . The particle size of sand found at this gully site was 90.2%, silt 5.4%, sand 86.2%, and clay 6.4%.

Source: Field work, 2021. Plate 3: A typical gully site in Akurba, Lafia LGA Gully found in Adogi recorded in a gully length of 256m, with a gully width of 6m, gully depth of 5.3m, and covering an area of 1536m 2 . In terms of particle sizes recorded at Adogi site, sand had 90.2%, silt 3.4% and clay 6.4%. In Kilema, the gully found recorded a length of 315m, width of 21.2m, and depth of 8.2m. In the same vein, this gully covered an area of 6678m 2 , with particle sizes of; sand 91.2%, silt 3. Plate 2: A typical gully site in Kilema, Lafia LGA At Tudun-Allu site of the study area, the gully found covered an area of 2772m 2 , with a depth of 7m, width of 11m and a length of 252m. In terms of particle size, Tudun-Allu site has the following underlying material; sand 90.2%, silt 3.4% and clay 6.4%. The second largest gully recorded in Lafia Local government Area in the course of the study, was at Ungwa Shawu. The gully found in this site covered an area of 5542.8m 2 , with a depth of 14m, a width of 18.6m and a length of 298m. The particle size found at this site has the following; sand 88.2%, silt 4.4% and clay 9.4%. Plate 4: A typical gully site in Ungwa Shawu, Lafia LGA Another large gully recorded in Lafia Local Government Area was found in Ungwa Tiv. The gully found at this site covered an area of 2541m 2 , with a gully length of 154m, gully depth of 10m and a gully width of 16.5m. more so, the particle size distribution recorded at this site had the following; sand 91.2%, silt 3.4% and clay 5.4%.

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The results also revealed the presence of medium size gullies in the study area, as well as small size gullies. The medium size gullies recorded in the study area were found in Bukan-kwato, Gandu, Gimare, and Kwandere respectively, while the recorded small size gullies recorded were found in Akunza and Danka. At Bukan-Kwato site, the medium size gully recorded covered an area of 666m 2 , with a gully depth of 5m, length of 111m and a gully width of 6m. The particle size at this gully site were; sand 86.2%, silt 4.4% and clay 9.4%. In Gundu site, the medium gully recorded had particle size distribution of clay 9.4%, silt 3.4% and sand 87.2%, covering an area of 676.5m 2 , with a depth of 7m and a width of 5.5m, while the length of the gully was 123m. This site recorded particle size distribution of; clay 9.4%, silt 3.4% and sand 87.2%. Similarly, the medium gully in Gimare site covered an area of 1016m 2 . In terms of length, width and depth, gullies recorded at this site had a length of 127m, width of 8m are were 6m deep. The particle size recorded at this site were sand; sand 88.2%, silt 5.4% and clay 8.4%. In Kwandere site, the medium size gully recorded had a length of 112m, covering an area of 784m 2 , with a width of 7m and depth of 6.5m. The particle size distribution included; sand 91.2%, silt 3.4%, and clay 5.4%. The small size gully recorded in Danka site had a particle size distribution of; sand 92.2%, silt 2.4% and clay 5.4%. This gully covered and area of 390m 2 , and recorded a gully length of 78m, gully width of 5m, and a gully depth of 5.7m. Similarly, Akunza site has a particle size distribution of sand 84.2%, silt 5.4% and clay 10.4%. In the same vein, the geometric characteristic, Akunza site recorded a depth of 6m, width of 5m, covering an area of 440m 2 with a length of 88m.

These findings are in agreement with Patrick (1999), Kurar and Jung (2005) (Mala, 2019). Texture of soil certainly affect soil erosion. Soil texture has its influence on infiltration or entry of water into the soil. When rainfall infiltrates rapidly, runoff is minimal thus erosion is less but when otherwise then erosion is much Mala. (2019). Clay is more resistant to erosion than sand. From the results in Table 1, it revealed that soil texture in the study area is more of Sandy-Loam. The implication was that it promotes erosion because Sand-Loam texture are not resistant to erosion (Mala, 2019).

14. b) Volume of Soil Loss in the Study Area

From the data presented in Table 3, it can be observed that in Adogi the volume of soil loss due to gully erosion in the area was 13037.8tons, while 11643.2tons of soil loss was recorded in Akunza site. In the same vein, 7483.2tons of soil loss was recorded in Akurba site, while Bukan-kwato had a soil loss of 12574.9tons. The data presented further indicates soil loss of 14361.2tons in Danka site, while 10005.4tons of soil loss was recorded at Gandu site. Kilema, Kwandere, and Tudun-Allu sites recorded soil losses of 10118.1ton, 10195.3ton, and 35195.6tons respectively, while Ungwa Shawu and UngwaT iv sites recorded soil losses of 25173.6tons and 2156.9tons respectively.

The mean volume of soil loss in the study area as result of gully erosion was 13108.7tons with a standard deviation of 8924.5. The coefficient of variation of soil loss in the various gully sites in the study area was 68.1tons. From the results presented in the table (Table 3), Tudun-Allu and Ungwan Shawu suffers more soil loss as a result of gully erosion in Lafia Local Government Area of Nasarawa State. The implication here is that urban settlements and building structures in this area are at a high risk of collapse, and in the occurrence of such scenario lives and properties will be lost (Dalil, et al., 2016;Ibrahim, et al., 2017).

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The above findings in respect to the volume of soil loss in the study area coincides with Baver et al. (2002), who were of the position that the effect of soil properties on water erosion can be in two ways: Firstly, certain properties determine the rate at which rainfall enters the soil. Secondly, some properties affect the resistance of the soil against dispersion and erosion during rainfall and runoff. The particle size distribution is an important soil property with regards to erodibility. Generally, it is found that 35% clay are often regarded as being cohesive and having stable aggregates which are resistant to dispersion by raindrops (Evans, 2015). Evans also stated that sands are not easily eroded by water due to its high infiltration rate. In contrast soils with a light silt or fine sand fraction are very erodible. The depth of erosion is determined by the soil profile (Evans, 2015). According to Evans soil horizons below the A horizon or plough and chemical composition of the sub surface horizon can also have an adverse affected. Normally deep gullies can be cut if the parent material is unconsolidated.

17. c) Morphometry of Gullies in the Study Area

The results presented in Table 4 establishes the morphometry of gullies in the study area. From the results, gully Morphometry are presented in respect to the gully size. Small gullies in the study area recorded a mean length of 83.0m. In the same vein, the mean depth of small gullies in the study area was recorded at 5.9m, with a slope angle surface of 7.6 o on which gullies develop. Medium gullies in the study area recorded a mean length of 118.3m. The mean value of the depth of this size of gully was estimated 6.1 with a slope angle of 8.8 o on which gullies develop. For large gullies in the study area, mean gully length was estimated at 260.0m. Furthermore, the mean value of gully depth for this size of gully was estimated at 9.4m, with a 5.5 o slope surface angle on which gullies develop. The results in Table 5 further reveals the morphometry of gullies in the study area in terms of their slope profile. From the results, it can be observed that the mean length of slope of gullies in the study area was 17.2m, with a coefficient of variation of 31.4m. Furthermore, the mean slop angle on which gullies develop in the study area was 5°, with a coefficient of variation of 52. These findings are in line with the work of Udosen (1999) on morphometry of gullies in Abutme area of Akwa-Ibom State, Nigeria. 6 reveals the Pearson correlation coefficient between the length and the depth of gullies in the study area at 0.614. This coefficient thus implies a strong positive linear relationship/association between the length and depth of gullies in the study area. More so, the 1-tailed test revealed a statistically significant relationship, with a significant value (p-value) of 0.017.

Similarly, the results also revealed a strong positive leaner relationship/association between the area of gullies and width of gullies in the study area. This strong positive leaner relationship was found to be statistically significant with a 1-tailed test at 0.01 level, with a significant value (p-value) of 0.000. These results by implication, implies that there is a strong positive relationship between the length and depth of gullies, as well as the area and depth of gullies in the study area. The findings of these correlation results are in line with the work of Udosen (1999). In assessing the morphology of gullies in the study area, the study took into consideration the shapes of gullies in the study area, the various classes of gullies in the study area, as well as the stages of gullies development in the study area. The results presented in Table 7 shows the morphology of gullies in the study area. In determining the various classes of gullies in the study area, the methods of Ireland, et al. (1996) and Leopol and Miller (1956) were employed. From the results presented in the Table 4.5, it can be observed that 44.4% of the gullies in the study area are discontinuous gullies, while 55.6% were continuous gullies. Discontinuous gullies are characterized by respectively low or gentler gradients and they are caused by local over-steeping of slopes due to aggravation. This method was applied by Heede (1974, 1970, and 1976), Cudoson, (2005), and Blon (1966,1970) in the north island of New Zealand. Mosley (1972), recorded in Bocco (1990) studied a discontinuous gully system in alluvial fills in the Colorado piedmont (USA). In this study, the characteristics of gully morphology were agent which operates frequently during heavy rain or strong winds. Gully system is said to be discontinuous when it reached it shape of maturity. Heede (1975) in an attempt to predict gully growth and guide consideration works combine the concept of discontinuity with that of stages of cyclic gully development. Based on field observation on the flanks of the Rocky Mountains (USA), he noted that discontinuous gullies represent youthful stages in gully development. Continuous gullies. These gullies in the study are at their 5% and above development. The stage of gully development consists of the development of the channel cut through the top soil and upper 'B' horizon. The early stage of a continuous gully, characterized by several knick points on the channel both on, can be termed the 'early mature' of development (Bocco, 1991).

The morphology of gullies in the study area in terms of the stages of gullies development was also analysed in line with the study of Heede (1975). From the results presented in the Table 7, 58.3% of the sampled gullies were at a stable state of development, while 41.7% of the gullies were at an unstable state of development. In respect to the shapes of gullies in the study area, in line with the study of Heede (1975), 38.9% of the sampled gullies were long-narrow gullies, while 22.2% were linear shaped gullies. In the same vein, rectangular shaped gullies found in the study area consisted of 22.2% of the sampled gullies in the study area, while 13.9% of the sampled gullies in the study area were trapezoidal shaped gullies. Long-narrow and rectangular shaped gullies consisted of 2.8% of the sampled gullies in the study area.

18. f) Mapping of Areas Affected by Gully Erosion in the Study Area

The effects of gully erosion in an environment can be control if only the most prone areas are properly mapped out, and precautionary measure are taken (Leopold et al., 1964, andMackin, 1948). Thus, the various areas affected by gully erosion in the study area were mapped using the coordinates collected from the identified site and depicted in Figure 3

19. Conclusion

This study assessed the Morphometry of gullies in Nasarawa State. Nasarawa State is facing severe problem of gully erosion, causing untold hardship and depression on the lives of the people of the State. Complex interdependent mechanism between rainfall characteristics, soil erodibility, land use, and topography has reduced infiltration, which caused a higher surface runoff. This has increased deep cutting, take up valuable land, raised the cost of living, and raised the cost of building and sinking of well water. The chain of the cause and effects hints most of the low-income groups of the communities where the population density is highest and where the worst damages of gully erosion are found. The paradigm of sustainable development requires equality and harmony of environment, economy, and society. And sustainable development is not possible unless this equality is felt by the masses.

Environmental degradation leads to resource degradation, declining standards of living, the extinctions of large numbers of species, health problems in the human population, conflicts between groups fighting for dwindling resources, water scarcity and many other major problems (UNESA, 2002). If this trend is allowed to continue, the long run impact of environmental degradation would result in local environments that are no longer able to sustain human populations. Such degradation on a global scale would, if not addressed, can lead to the extinction of human life on earth. In order to achieve sustainable development, a conscious effort needs to be made today to sustain the environment and prevent further degradation; various local, regional and national governments and local, regional, national and international agencies needs to work together towards promoting environment friendly lifestyle and protecting the fragile ecosystems of the planet.

V.

20. Recommendations

On the basis of the findings of the study, the following recommendations were made;

1. Gully extent magnitude can have controlled grazing, conservation farming of vegetation barriers against run-off, especially around fresh gully leach-cats as measure of combating gully erosion in the affected areas. 2. The soil of Nasarawa State can be conserved from gully erosion by the construction of check-dams, vegetative catchment barriers and grass water ways across the gullies in order to reduce the volume of soil loss in the area. 3. Areas that are affected and vulnerable to gully erosion could be allocated to special uses. For example, such vulnerable area could be used for wild life and recreational purposes.

Figure 1. Fig. 1 :
1Fig. 1: Map of Lafia Local Government Area. Lafia Local Government Area of Nasarawa state is located between latitudes 8° 20' and 8° 38'N and between longitudes 8°20' and 8°40'E. Lafia Local Government area has a land area of 2,797.5sq.km with a population of 330,712 (NPC, 2006). It is bordered by Nasarawa -Eggon Local Government Area and Wamba Local Government Area to the north, Doma Local Government Area to the west and south and Obi Local Government Area and Shendam Local GovernmentArea in Plateau State to the east. Lafia's location at the junction of a regional road confers on its good linkage with Makurdi, Benue state to its south, Akwanga-Keffi and Abuja to its north-west and Jos, Plateau state its north-east.
Figure 2.
91
Figure 3.
parameterizing, combining and classifying erosion physical factors in quantifying soil loss in the general landscape (Renard, Foster, & Weesies, 1997). The erosion physical factors include: rainfall, erosivity, soil erodibility and slope length (Weesies, 1997). A=R×K×LS While a soil erosion study that involve agricultural land use and watershed, a biophysical factor could be used. Biophysical factors include: rainfall erosivity, soil erodibility, slope length, cover and management practices, and supporting practices factors. This can be illustrated in the formulae as follows: A=R×K×LS×P×C Where; A= Average annual soil loss (Ton/ha/yr), R= Rainfall erosivity factor (mj/mm/ha/yr), K= Soil erodibility factor (ton ha/mj/mm), LS= slope length factor, C= cover and management factor and P= supporting practice factors The procedures for estimation of these factors and soil loss can be found in many studies (Farhan, Zregat, & Farhan, 2013; Ghosh, De, Bandyopadhyay, & Saha 2013; Javed, Yasser, Shams Al-Deen, & Mohd, 2014; Kamaludin et al., 2013; Khosrokhani & Pradhan, 2014, Garedew, & Yimer, 2015).
Figure 4.
(2012), Seutloali et al. (2015), and Mallam et al. (2016).
Figure 5.
(2012), Seutloali et al. (2015), Mallam et al. (2016), and Dalil et al. (2016).
Figure 6.
(2012), Seutloali et al. (2015), and Mallam et al. (2016).
Figure 7.
4 and clay 5.4%. It is important to point out here that Kilema had the largest gully recorded in Lafia Local Government Area, during the course of this study. Volume XXI Issue III Version I 94 ( ) Source: Field work, 2021. Plate 1: A typical gully site in Adogi, Lafia LGA Source: Field work, 2021.
Figure 8. Table 1 :
1
S/ Gully Site Length Area Width Depth Cross Particle Size (%) Textural
N (m) (m 2 ) (m) (m) Section class
Sand Silt Clay
Lafia LGA
1 Adogi 256 1536 6 5.3 V and U Shape 90.2 3.4 6.4 Sandy-Loam
2 Akunza 88 440 5 6 U-Shape 84.2 5.4 10.4 Sandy-Loam
3 Akurba 285 4930.5 17.3 12 U-Shape 86.2 5.4 8.4 Sandy-Loam
4 Bukan-kwato 111 666 6 5 U and V Shape 86.2 4.4 9.4 Sandy-Loam
5 Danka 78 390 5 5.7 U-Shape 92.2 2.4 5.4 Sandy-Loam
6 Gandu 123 676.5 5.5 7 U-Shape 87.2 3.4 9.4 Sandy-Loam
7 Gimare 127 1016 8 6 U-Shape 88.2 5.4 8.4 Sandy-Loam
8 Kilema 315 6678 21.2 8.2 U-Shape 91.2 3.4 5.4 Sandy-Loam
9 Kwandere 112 784 7 6.5 U-Shape 91.2 3.4 5.4 Sandy-Loam
10 Tudun-Allu 252 2772 11 7 V-Shape 90.2 3.4 6.4 Sandy-Loam
11 Ungwa Shawu 298 5542.8 18.6 14 U-Shape 88.2 4.4 9.4 Sandy-Loam
12 Ungwa Tiv 154 2541 16.5 10 V-Shape 91.2 3.4 5.4 Sandy-Loam
Source: Field and laboratory analysis, 2021.
Figure 9. Table 2 :
2
S/N Gully Site Latitude (N) Longitude (E) Magnitude
Sites in Lafia LGA
1 Adogi 8° 29' 46"N 8° 30' 2"E Large gully
2 Akunza 8° 28' 6"N 8° 36' 14"E Small gully
3 Akurba 8° 29' 29"N 8° 30' 25"E Large gully
4 Bukan-kwato 8° 28' 16"N 8° 35' 14"E Medium gully
5 Danka 8° 29' 16"N 8° 30' 56"E Small gully
6 Gandu 8° 29' 19"N 8° 30' 42"E Medium gully
7 Gimare 8° 29' 45"N 8° 30' 7"E Medium gully
8 Kilema 8° 29' 34"N 8° 30' 19"E Large gully
9 Kwandere 8° 29' 23"N 8° 31' 16"E Medium gully
10 Tudun-Allu 8° 29' 44"N 8° 32' 9"E Large gully
11 Ungwa Shawu 8° 29' 43"N 8° 32' 5"E Large gully
12 Ungwa Tiv 8° 29'31"N 8° 31' 31"E Large gully
Source: Field work, 2021.
Figure 10.
Figure 11. Table 3 :
3
S/N Gully Site R K LS Volume of Soil Loss (tons)
1 Adogi 265.86 219.7 20 13037.8
2 Akunza 265.86 196.2 20 11643.2
3 Akurba 265.86 126.1 20 7483.2
4 Bukan-kwato 265.86 211.9 20 12574.9
5 Danka 265.86 242.0 20 14361.2
6 Gandu 265.86 168.6 20 10005.4
7 Gimare 265.86 90.3 20 5358.7
8 Kilema 265.86 170.5 20 10118.1
9 Kwandere 265.86 171.8 20 10195.3
10 Tudun-Allu 265.86 118.2 20 35195.6
11 Ungwa Shawu 265.86 424.2 20 25173.6
12 Ungwa Tiv 265.86 120.6 20 2156.9
Mean Value of Soil Loss 13108.7
Std. Deviation 8924.5
CV of soil loss in Lafia LGA 68.1
Source: Field and Laboratory work, 2021.
Figure 12. Table 4 :
4
Gully Size Mean values of gully length (m) Mean values of gully depth (m) Slope angle surface on which gullies develop
Small gullies 83.0 5.9 7.6 o
Medium gullies 118.3 6.1 8.8 o
Large gullies 260.0 9.4 5.5 o
Note: Source: Field work, 2021.
Figure 13. Table 5 :
5
98
Volume XXI Issue III Version I
)
(
S/N Gully Site Length (m) Slope angle (in degrees)
1 Adogi 20 8 o
2 Akunza 20 7 o
3 Akurba 20 6 o
4 Bukan-kwato 20 6 o
5 Danka 20 2 o
6 Gandu 20 3 o
7 Gimare 10 9.5 o
8 Kilema 10 3 o
9 Kwandere 20 5 o
10 Tudun-Allu 20 2 o
11 Ungwa Shawu 6 2 o
12 Ungwa Tiv 20 7 o
Mean 17.2 5 o
SD 5.4 2.6
CV 31.4 52
Source: Field work, 2021
Figure 14. Table 6 :
6
Correlations
Length of gullies (m) Dept of gullies (m)
Length of gullies (m) Pearson Correlation 1 0.614 *
Sig. (1-tailed) 0.017
N 12 12
Dept of gullies (m) Pearson Correlation 0.614 * 1
Sig. (1-tailed) 0.017
N 12 12
*. Correlation is significant at the 0.01 level (1-tailed).
Area of gullies (m 2 ) Width of gullies (m)
Area of gullies (m 2 ) Pearson Correlation 1 0.951 **
Sig. (1-tailed) 0.000
N 12 12
Width of gullies (m) Pearson Correlation 0.951 ** 1
Sig. (1-tailed) 0.000
N 12 12
**. Correlation is significant at the 0.01 level (1-tailed).
Source: Author's computation, 2021.
e) Gullies Morphology in the Study Areas
Figure 15. Table 7 :
7
S/N Gully Site Gully Shape Gully Class Stage of Gully Development
Sites in Lafia LGA
1 Adogi Long-narrow Discontinuous gullies Unstable
2 Akunza Trapezoidal Discontinuous gullies Unstable
3 Akurba Rectangular Discontinuous gullies Stable
4 Bukan-kwato Long-narrow Continuous gullies Stable
5 Danka Long-narrow Discontinuous gullies Stable
6 Gandu Linear Discontinuous gullies stable
7 Gimare Rectangular Discontinuous gullies Unstable
8 Kilema Trapezoidal Discontinuous gullies Unstable
9 Kwandere Linear Continuous gullies Stable
10 Tudun-Allu Long-narrow Discontinuous gullies Stable
11 Ungwa Shawu Trapezoidal Discontinuous gullies Unstable
12 Ungwa Tiv Long-narrow Discontinuous gullies Stable
1
2
3
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Notes
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© 2021 Global Journals
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Morphometric and Morphological Analysis of Gullies in Lafia Lga, Nasarawa State, Nigeria
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B © 2021 Global JournalsMorphometric and Morphological Analysis of Gullies in Lafia Lga, Nasarawa State, Nigeria
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B© 2021 Global Journals
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Date: 2021-07-15