Fluvial Geomorphological Characterization of River Magarya in the Upper Gongola Basin, Northeastern Nigeria: An Integrated Dem, Saga-GIS and Field Approach

River longitudinal profiles provide important insights into landscape evolution, tectonic processes, lithology, and human impacts; however, the geomorphology of many tributaries within the Gongola Basin in northeastern Nigeria remains undocumented. This study examines the geomorphological characteristics along the 30.1 km longitudinal profile of River Magarya in Akko LGA, Gombe State, through an integrated application of remote sensing, GIS, and fieldbased measurements. The catchment was delineated from a 30m SRTM DEM using Golden Surfer 24 and SAGA GIS 7.8, incorporating a Machine Vision approach. GPS and ranging poles were used to measure longitudinal and cross-profiles in the upper, middle, and lower river courses. Landforms were identified through the geomorphon algorithm and verified by manual field observation. Changes in land use/land cover between 1993 and 2023 were evaluated through supervised Landsat classification in ArcGIS 10.8. The findings indicate that the catchment encompasses 130.2km², including 5 sub-catchments and 112 tributaries with a combined stream length of 140.2km. Elevation decreases from 630m at the source to 275m at the confluence, producing an average gradient of 11.8m/km. Cross-profile results identify a flatbottomed, sand-filled valley in the upper course, measuring 19.3 m in width and 4.9 m in depth, which developed on friable Kerri-Kerri sandstone; a gorge in the middle course, measuring 73.2 m wide and 34.6-47 m high; and a broad, U-shaped lower-course valley containing point bars. Nine geomorphons were classified automatically, whereas 29 landforms were identified manually. The built-up area expanded from 4.4% to 18.8%, thick vegetation decreased from 18.5% to 9.3%, and open spaces grew from 17.9% to 41%. The study concludes that lithological differences among the Pindiga, Gombe Sandstones, Yolde, and Keri-Keri formations exert strong control over channel morphology along River Magarya, with this influence compounded by intense anthropogenic pressure associated with urban expansion and deforestation. On the basis of the identified characteristics, the study recommends constructing check dams and gabions in the gorge section to regulate runoff and limit downstream sedimentation; afforesting the flatbottomed upper course with vetiver grass and economic trees to stabilize the friable sandstone; enforcing a 100 m buffer zone that prohibits sand mining, rice mills, and farming along the middle and lower courses; and implementing community-based watershed management to regulate urban expansion and fuelwood extraction.