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International Journal of Environment, Ecology, Family and Urban Studies (IJEEFUS) ISSN 2250-0065 Vol. 3, Issue 4, Oct 2013, 23-30 Š TJPRC Pvt. Ltd.

CHANGES IN CHANNEL MORPHOLOGY AND ITS SOCIO ECONOMIC IMPACT ON THE RIVERINE COMMUNITIES IN YOLA AREA ABUBAKAR, BASHIR Department of Geography, Modibbo Adama University of Technology, Yola, Nigeria

ABSTRACT Flood Plains attract and support wide range of human activities due to the fertile soil, the flat topography and proximity to sources of water. This Paper examines the socio-economic implication of changes in channel morphology especially changes in channel width as it affect the production of crop in the adjacent land. The Channel width was measured on satellite Images namely LandSat MSS Image of 1975, LandSat ETM Images of 1987 and 2005. Data on the socio-economic Impacts of the changes were sourced from questionnaire administration, a total of 300 copies of questionnaires was administered to randomly selected respondents in the nine purposively selected riverine communities. The results revealed that majority of the respondents are engaged in Land based economic activities,an average of 55.1% and 13.4% are engaged in farming and grazing respectively. An average 61% have their farmlands located less than 100 metres away from the channel bank, these along with other factors expose the respondents to vagaries of changes in the channel morphology with losses in farm produce as a result of increasing incidence of bank erosion which causes channel widening.

KEYWORDS: Flood Plain, Channel Morphology, Channel Width, Channel Bank INTRODUCTION Fluvial landscapes are areas that attracts a wide range of human activities mainly agriculture and settlements; this is due to the well drained flat topography and fertile soil that exist in the riparian corridor. The riparian corridor presents a wide range of economic advantages that attract land based economic activities such as agriculture production and urban development and these have far reaching consequences on the flow morphology of the channel. The intensive human activities in the corridor upsets the dynamic equilibrium between a stream and its flow plain coursing accelerated erosion, channel incision and bank failure (Ward and Trimble, 2004) there process have significant socio economic effects on the riparian communities Previous Studies such as Kusimi (2008) has established the interrelationship between changes in the controlling factors that affect channel morphology and their consequences on the economic interest of the adjacent communities, of the Densu River in Ghana, analysis of satellite imageries of the Densu basin suggested a swift change in the land cover, mainly causing a large scale change in the rate of sedimentation of the bank to the turn of 475.641 tons/ day which limits the capacity of the Densu River and limits its utility as a major source of water in the region. The changes in land use/ land cover along the study segment of this research could also be the cause of the limitation of river Benue as a water way and source of water to the riparian settlement. Loss of adjacent land as a result of excessive bank erosion is another socio economic consequences of changes in channel morphology, especially changes in channel width. Yamani, et al (2011) studied the effect of human activities on bank stability of Atrak river in North East Iran, using a combination of satellite images, aerial photographs and field work. Where as the result indicated changing land cover as the main cause of changes in the channel morphology, however the


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Abubakar, Bashir

changes have wide range of implications such as the destruction of villages, bridges, roads and recurrence of river flooding which are all causing a lot of social and economic damages to the riparian population. Shields et al (2000) in their study of a channel reach migration as a result of reservoirs on Missouri river U.S.A using hydrometerological data were able to establish a trend of the channel migration, mainly through bank erosion which adversely affected the adjacent land at a rate of 0.12 ha per river km, with socio economic impacts including the loss of agricultural land, irrigation pumping stations and pipelines damage. Extensive land degradation was also reported among land owners as most of the land owners contend with the degradation of the high quality flood plain land to lower elevation deposits of soils that are coarse and less fertile. Roksandic etal (2011) in their studies of the socio economic implication of bank erosion of the Kolubara river basin Serbia, reported a cumulative lost of about 60.37 ha of land, which has resulted to the displacement of villages and families along the channel. Another important socio economic consequences of the change in channel morphology is the compromising of ecological integrity of channel as habitat for fishes and other aquatic species. The adverse effect of damming of river has been established by Dynesios and Milson (1994) to cause a disconnect between river and their flood plains, wet lands and reduces the channel velocity and effects the migration pattern of fishes . In the Benue system, previous studies Asriel, 2007, established that channels in the physical habitat and hydrology of the river Benue occasioned by human impacts is responsible for 93% of decline of fresh water fauna within the riverine communities. This implies a reduced fish catch which has a far reaching implications on the house hold income within the communities studied. The main thrust of this paper is therefore, understanding the nature of this changes and their consequences on the socio economic activities of the land uses along the channel of river Benue. The pepper aimed at determining extent to which channel discharge change and changes in land use land cover within the river Benue catchment contributed toward morphological changes at the river Benue and its social and economic consequences on the adjacent repairing communities.

STUDY AREA The Study area selected for this study is a segment of river Benue of a length of 54 km situated between latitude 0

I

9 02 and 90 30I N 120 20I to 120 54I E. river Benue is a major tributary of river Niger and it the major river traverses Adamawa State. The selegion of their segment and catment drained by the river could be justified by the fact that it support substantial population of mainly rural farmers, pastries and fishing communities in a rural areas that have a functional relationship with Jimeta and townships with are the major urban centres within the catchment. The population of the area is 20,855, (NPC 2006). The area has a typical tropical savannah climate with distinct wet and dry season. The rainy season last for an average of 6 months from May to October, with an average of 41% of their rain falling in august and September. The main annual rain fall ranges between 850mm – 1000mm. all location within the study area have a fairly uniform climate as they are in the same latitude, and on flat terrain devoid altitudinal influence on the local climate. The topography of the area is generally low landing flat terrain of 183.3 – 200 metres asl with gentle undulation and hills ranges purchasing the extensive flat flow plain at various locations notably across the river Benue (from Jimeta). Eastward, the land rises steeply to attend a maximum height of 240metres above mean sea level (Makpene 2007) the geology of the area is made up of two main geological units namely; the Bima sandstone and the alluvial sand deposit. Alluvial sand deposit formed the bank material which continue the river, it is a recently deposit sandy loan deposit with very low cohesion.


Changes in Channel Morphology and its Socio Economic Impact on the Riverine Communities in Yola Area

25

The vegetation cover around the channel segment was a woody savannah made up of gallery of different plant species; however, the primary vegetation in the area has since being replaced with a secondary vegetation mainly that constitute a pastoral block (Tukur and Ardo,1999). The effect of human activities increased the vulnerability of the channel morphology to changes.

Figure 1: The Study Area Showing the Sampled Riverine Communities

MATERIALS AND METHODS The materials used for this study are LandSat MSS image of 1975, LandSat ETM images of 1987 and 2005. the channel segment was extracted from the images and the channel width (which is one of the morphological variables) was measured on the multi temporal images. Channel depth was also measured at very homogenous reaches of the segment; the measurement of the channel depth was done using Surveyors’ Staff and the measurement was taken at rainy and dry season from which an average depth was computed. The information on the socio – economic implications of the changes in the morphological variable (namely channel width and channel depth) was gathered through administration of questionnaires to randomly selected respondents. The administration of the questionnaires was preceded by the selection of the reverie communities that are most affected by the changes in the channel morphology, a purposive sampling of the 9 (nine) communities was undertaken and a total of 300 copies of questionnaire were proportionately distributed to randomly selected respondents as presented on the table below. Table 1: Sample Size for Questionnaire Administration Project. % of Total Copies of Questionnaire Population Population Administered Dasin Hausa 3,946 27.6 83 Lugga 711 5.0 15 Semde 206 1.4 5 Njoboliyo 2,572 18 54 Fasare 690 4.8 14 Kabawa 1,347 9.4 28 Kangli 1,203 8.4 25 Kwaine 486 3.4 10 Gereng 3,132 21.9 66 Total 14,293 100 300 N: B Computed from 2006 Census data using 1991 Census figures and 2010 Voters’ Register. Source: National Population Commission (1991/2006) Community


26

Abubakar, Bashir

The data was presented in frequency table and percentage for easy comprehensive and cross comparison.

RESULTS AND DISCUSSIONS The basic factor that predisposes the inhabitants of the reverine communities to the impact of changes in channel morphological variable is their socio economic disposition such as nature of occupational distribution, income, level of education, nature of land ownership and tenure practice. Thus table 2 presents the socio economic profile of the respondents: Table 2: Socio Economic Profile of the Respondent Socioeconomic Variables

Dasin Hausa

Lugga

Farmers Pastoralist Fishermen

74.7 15.7 9.6

60 26.7 13.3

>10 15-Oct 15-20 <20

7.2 9.6 20.5 62.7

20 53.3 29.7

Formal Educ. Informal Educ. Uneducated

8.4 79.5 12.04

26.7 40 6.7

88

60

60

74.1

8.4

26.7

40

3.6

13.3

-

Individual Ownership Communal Ownership Open Access

Semde

Njoboliyo

Fasare

Kabawa

Kangli

Kwaine

Gereng

35.7 17.9 46.6

60 08 32

50 10 40

68.2 4.5 27.3

14.3 28.6 21.4 35.7

12 24 28 36

10 50 20 20

4.5 22.7 39.4 33.3

14.3 28.6 57.1

12 32 56

10 30 60

10.6 45.5 43.9

64.3

71.4

84

80

87.9

16.7

21.4

17.9

12

20

9.1

9.2

14.3

10.7

04

-

03

Main Occupation 40 50 57.1 9.3 28.2 60 40.7 14.7 Avr. Monthly Income (000) 3.7 40 9.3 7.1 40 16.7 50 20 70.3 42.9 Educational Attainment 20 20.4 21.4 40 31.5 57.2 40 48.1 21.4 Pattern of Land Ownership

The analysis of the socio economic profile of the respondents shows that majority are employed in land based economic activities with an average of 60 - 80% of the respondents engaged in farming and rearing of live stocks, thus any change in morphology of the river Benue especially changes in channel width will have a profound effect on the crop production more especially if the changes in channel width is considered pari passu to the relative location of the farmlands from the channel bank as presented in the tables 3a and 3b Table 3a: Variability in the Changes in Channel Width along the Channel Segment Reaches 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Width 1975(m) 392 484 504 413 404 560 606 631 479 357 488 548 432 454 464 851

Width 1987 (m) 299 259 222 315 315 259 311 410 280 399 235 410 297 333 346 420

Width 2005(m) 347 447 379 544 544 415 541 432 368 413 368 340 450 293 238 321

% Change in Width b/w 1975- 1987 -23 -46.5 -55.95 -23.7 -22.02 -53.8 -48.7 -35.02 -58.3 +11.8 -51.8 -25.2 -31.3 -26.7 -25.43 -50.6

%Change in Width b/w 1987-2005 +16.05 +58.30 +70.7 +72.7 +72.7 +60.2 +73.95 +5.4 +31.4 +3.5 +56.6 -17.07 +51.5 -12.01 -31.2 -23.6


27

Changes in Channel Morphology and its Socio Economic Impact on the Riverine Communities in Yola Area

Table 3a: Contd., 17 568 387 476 -31.9 18 587 321 265 -45.3 Mean 512 323.2 409 S. Dev 111.6 63.3 80.3 CV(%) 21.8 19.6 19.6 NB: (+) indicates widening, while (-) indicates narrowing

+22.9 -17.4

Table 3b: Estimated Distance of Farmland from the River as Reported by the Farmers (%) Community Dasin Hausa Lugga Semde Njoboliyo Fasare Kabawa Kangling Kwaine Gereng Mean

Less than 100 Metre 74.2 44.4 50 66.7 62.5 40 60 80 71.1 61

100– 150 Metre 14.5 22.2 50 18.5 25 20 20 20 11.1 22.4

150 – 200 Metre 6.5 22.2 11.1 12.5 10 13.3 13.3 9.9

over 200 Metre 4.8 11.2 3.7 30 6.7 6.7 6.7

The changes in channel width translated to loss of adjacent land which is a permanent economic lost to the riverine communities, however the immediate loss is the loss in crops that are planted on the adjacent farm land as presented in table 4. Table 4: Average Annual Crop Yield Lost as a Result of Change in Channel Morphology Location Dasin Hausa Lugga Semde Njoboliyo Fasare Kabawa Kangling Kwaine Gereng Mean

100 – 500kg 9.5 33.3 100 25.9 25 20 26.7 22.2 29.2

600 – 1000kg 64.5 55.6 59.3 62.5 70 60 80 66.7 57.6

Above 1000kg 25.8 11.1 14.8 12.5 10 13.3 20 11.1 13.2

The losses reported on Table 4. Are the cumulative loses of the different crops produced by the farmers along the river bank. This may not give an insight into the actual loses in economic terms due to the difference in the prices of the products. Thus, averages of 57.6% of farmers have reported a loss of 600 - 1000 kg of crops mainly cereal. It is important to note that higher losses were recorded in Dasin where 25.8% reported losing over 1000kg of crops; a higher proportion of the farmers had their farm land proximately located near the river channel (refer to Table 3b). It is therefore safe to infer that the quantum of crop loss is significantly determined by the relative location of individual farmlands from the channel. The pattern of land ownership presented on table 2, where individual land ownership predominated would have ensured a more sustainable management of the land through bank stabilization and other land management practices, however, the low income of the respondents have influenced their perception and response to the changes that occurred as presented on table 5a and b.


28

Abubakar, Bashir

Table 5a: Nature of Changes Perceived by the Land Users Land Users Nature of Change Channel migration High incidence of land Erosion Reduction in thalweg depth Widening of river channel

Farmers (183)

Pastoralist (37)

Fishermen (80)

74.9% 9.8% 9.8% 5.5%

59.5% 18.9% 16.2% 5.4%

20% 5% 65% 10%

The perception of the nature of change is influenced by the nature of occupancy of the land by various land users along the river channel. Thus 75% and 60% of farmers and Pastoralist respectively noticed channel migration as a major change in the morphology, this could be attributed to the effect of the channel migration on the nature of the land use or occupation of these land users. 65% of fishermen recognized the reduction of thalweg depth as the major change, this is also due to the on channel nature of their occupation. A higher proportion of the fishermen reported cases of lower fish catch resulting from the negative effects of siltation on fish habitat and its limitation of navigation within the river. Based on the perception and the socio-economic disposition of the respondents, they responded to the changes through various means as presented in Table 5b. Table 5b: Response to the Effect of Channel Migration and Bank Erosion S/No 1. 2. 3.

Nature of Response Use of local materials for embankment. Shift in timing of land preparation and crop production . Indifference due to low income or non ownership of land Total

Frequency

Percentage

51

17

60

20

189

63

300

100%

The variation in the responses to the effects of channel migration and bank erosion presented on Table 5b is to some extent a reflection of the ownership structure of the lands along the segment. Thus out of the 63% of the respondents that are indifferent to the incidence of bank collapse or channel encroachment in to their lands, majority about 85% (who are farmers) do not own the lands on which they cultivate, they hold the land through a lease arrangement that limits their lost to only the crops cultivated on the land.

CONCLUSIONS The increasing intensity of agriculture along the bank of river Benue has exposed the inhabitants of the riparian communities to the vagaries of changes in the morphology of the river; and this has far reaching consequences on the micro economy of the communities. It is therefore pertinent to adapt measures that will ensure a sustainable management of the land resources within the corridors of the river Benue as a whole. These measured will include: ď&#x201A;ˇ

Afforestation programme, especially creation of Buffer zone along the river channel, this will facilitate a level of stability of the bank.

ď&#x201A;ˇ

Piece meal embankment of the channel especially in reaches that are critically affected by intensive human activities.

ď&#x201A;ˇ

Enlightenment of the riverine communities on the adoption of agro forestry and other measures that will reduces losses from changing river morphology.


Changes in Channel Morphology and its Socio Economic Impact on the Riverine Communities in Yola Area

29

REFERENCES 1.

Dynesius, M. and Nilsson, C. 1994. ‘Fragmentation and flow regulation of river systems in the northern third of the world’, Science, vol. 266, pp. 753–762.

2.

Kusimi, J. M.(2008) Analysis of Sedimentation Rates in the Densu River Channel: The Result of Erosion and Anthropogenic Activities in the Densu Basin. West African Journal of Applied Ecology, vol. 14, 2008 1

3.

ShieldsJR,F.D, Pezeshki, S. R, Wilson, G. V and Wu,W(2008) Rehabilitation of an incised Stream with plant materials: The dominance of Geomorphic Processes. Ecology and Society 13(2):54.

4.

Tukur, A.L and Ardo, M.B (1999) Livestocks In Adebayo, A.A and Tukur, A.L (edit) Adamawa State in Maps. Paracelete Publishers. Pp 44-47.

5.

Ward, A. D and Trimble S.W (2004) Environmental Hydrology, 2nd Edition CRC Press LLC Florida.

6.

Yamani,M, Goorabi,A and Dowlati, Javad (2011) The Effects of Human Activities on River Bank Stability

7.

(Case Study) American Journal of Environmental Sciences 7 (3): 244-247.


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