An Assessment Of Factors Affecting Gully Erosion And Its Control Methods In Three Selected Gully Erosion Sites In Abia State, Nigeria.

ABSTRACT

 Effective control of soil erosion involves the application of engineering and biological measures. The efficacy of these two normally recommended methods, was studied using three randomly selected gully sites in Abia state, Nigeria. Soil samples were collected and analysed for physical and chemical characteristics. Germination studies were conducted on seeds of two dominant tree species, Gmelina arborea and Anacardium occidentale, while inventory of the vegetation, including ground cover species was carried out. Slopes were measured and rates of sediment accumulation Were determined along with siltation duration. Comparisons were also made between the monetary contributions of Abia State government and local communities for gully erosion control, including funds expended on engineering constructions and afforestation. Results showed that soil physical and chemical properties and slope steepness, especially those exceeding 150 affected gully erosion incidence. The seeds of the dominant woody species had high germination propensity indicating that the great sustenance of afforestation using those species was a major control strategy. The gully site at Nkwoegwu, with the most abundant number of Mucuna sloaeni, had the highest amount of nitrogen fixation in its soil. The government (including UNDP) played dominant role in erosion control while local communities remained significantly lukewarm. Funds spent on engineering work (over 90%) was abnormally significant compared with that spent on biological control. The siltation duration (in years) for the three sites ranged between 537 and 946. Increased budgetary allocations for soil erosion control and greater involvement of local communities will largely be the best strategy in reducing erosion incidence in Abia State.