Assessment of Factors Affecting Ephemeral Gully Development in Badland Topography: A Case Study at Garbheta Badland (Pashchim Medinipur, West Bengal, India)

Abstract

Gully erosion in the Paschim Medinipur district of West Bengal, India has been an issue of anxiety, formed by the amputation of soil from narrow channels through the accretion of surface runoff. Here, we attempted to investigate the erosion variability of gully in a micro catchment area, and also scrutinized the gully cross-sectional areas as distinct components of gully volumes. Twelve gullies were randomly selected in different slopes. To determine the geometric growth of the gully dimensions and soil loss, the initial length of gully, the width of the gully and depth of respective gullies was monitored in different seasons. Univariate analysis was conducted to measure the association between gully head retreat and vegetation coverage, slope, rainfall volume and runoff contributing area. We found strong and significant relation between the slope of gully head and linear retreat in the pre monsoon (p < 0.008) and post monsoon (p < 0.024) season respectively. Conversely, rainfall volume and gully head retreat showed a strong relationship in the pre monsoon (r = 0.80), monsoon (r = 0.66) and post-monsoon period (r = 0.94); while meager relationship was observed with rainfall intensity (r = 0.06). Results also illustrated that the overall retreat of gully head had very strong and positive relationship with the runoff contributing area (r = 0.89, p < 0.001), and maximum gully erosion was observed in the monsoon period (55.67%). These results indicate that slope, rainfall and runoff contributing area have a strong positive influence on gully erosion in Paschim Medinipur district, since the initiation of the gully.