Morphometric Analysis of Gullies in Gombe Metropolis, Gombe State, Nigeria

This paper quantified gully morphological characteristics in Gombe metropolis, Gombe State. The purposive sampling procedure was used to select ten gully sites which are Tunfure, Arawa, Bolari East, Pantami, Liji, Bye Pass, Shamaki, Kagarawal, Mallam Inna area and Barunde for this study. Thereafter, the systematic sampling procedure was used at interval of 20m to segment the gully channels for data collection on gully morphological parameters such as gully length, depth, gully top and bed width, slope angle and cross sectional area. Descriptive statistics such as mean was used to show average values of the data set and the Pearson Product Moment correlation statistic was used to assess the nature and strength of the interrelationship between gully parameters. Results of the study shows that the measured sections of gully length in the study area ranged from above 100m to above 380m with a mean value of 125.69m, implying that the gullies in the study are medium to large gullies. Also, the gully top width ranged from 4.70m to 76.50m, implying that the top width strongly influences sediment delivery in the gully catchments. The gully bed widths ranged from 2.50m to 34.60m with a mean value of 14.40m, and the gully depths ranged from 1.30m to 18.90m. Moreover, the cross-sectional area ranged from 11.75m² to 1391.04m² with a mean value of 315.68m². The interrelationship between morphological parameters showed that there is strong positive relationship between the gullies’ top widths and bed widths (r = 0.89), indicating a concurrent adjustment between the two properties, given most of the gullies a V-shape and U-shape forms. This shows a fine adjustment to forms and processes, indicating lateral recession or gully side wall collapse due to mass wasting. It is concluded that gully erosion in the study area has gone to a disastrous level with severe impact on roads and houses, and it is therefore recommended that the Gombe State government should use engineering methods such as building of embankments to stabilise the gully banks and storm drains to remove excess runoff from the environment for controlled gully development in the area.

Keywords: Gombe State, Gombe metropolis, Gullies, Morphometric analysis