Assessment of Gully Erosion Hotspots in Anambra State Using Remote Sensing Techniques

Gully erosion in Anambra State represents one of the most severe land degradation challenges in Nigeria's South East geopolitical zone, with thousands of gullies documented across the state's highly erodible sandy loam soils and disrupted drainage systems. This study assesses the spatial distribution and characteristics of gully erosion hotspots across Anambra State using Sentinel-2 multispectral imagery and SRTM digital elevation data, supplemented by targeted field measurements. Object-based image analysis was employed in eCognition to identify and delineate active gully features based on spectral, textural, and morphological criteria. Gully morphometric parameters including length, width, depth, and volume were estimated through field survey at 45 randomly selected gullies across Orumba North, Nnewi South, and Ihiala local government areas. Topographic wetness index and slope gradient derived from the digital elevation model were tested as predictors of gully initiation probability using logistic regression. Results identify Orumba North as the local government area with the highest active gully density, with 312 mapped features covering an estimated 14 square kilometres of degraded land. Slope gradients exceeding 15 degrees and topographic convergence zones emerge as the strongest morphological predictors of gully initiation. The study recommends gully rehabilitation programmes using indigenous techniques including check dam construction and bioengineering, coupled with a geospatial monitoring system to track post-rehabilitation recovery. Keywords: gully erosion, remote sensing, Anambra State, land degradation, South East Nigeria.