Assessment of Landuse -Landcover Change and its Impact on Runoff Depth in the River Kilange Catchment, Adamawa State, Nigeria

Abstract

This study assessed landuse/cover change and its impact on runoff depth in the River Kilange catchment for the period (1994 to 2024) using the Soil Conservation Service-Curve Number (SCS-CN) Model. The data used in the study are soil map from the Digital Soil Map of the World (DSMW) and Shuttle Radar Topography Mission-Digital Elevation Model-SRTM-DEM (2019). Other secondary data are Landsat TM and OLI imageries for the years 1994 and 2024 respectively. The digital data were processed in Arc-Hydro and HecGeoHMS GIS Extensions, and the SPSS-16 statistical package was used to carry out the analyses. The results of analyses were presented in tables, charts and maps. The Upper-Kilange sub-catchment recorded the highest rate of landcover transformation, with 390% of other landuse/cover types converted to bare/cropland category. Loko subcatchment had relatively minimal landuse/cover change to bare/cropland with increase of 36.85 %. In the wood-forest landcover category, Lower-kilange had highest loss with 49.09 % decline, whereas Loko represents the least change with a decline of 11-39%. Runoff depth change in the study area during the study period follows the pattern of observed landuse/cover change. A 13.32% absolute increase in model-generated runoff was observed in the River Kilange catchment. Result of t-test, however, indicated the change difference between 1994 and 2024 was not statistically significant (P=0.68). This is likely due to high spatial variability among the sub-catchments considering the size of the study catchment, which is 5323 square kilometres. Increase in rock-outcrop and bare/cropland categories, and reduction in areas under wood forest, and shrub/grassland contributed to rise in runoff depth. This study recommends the regulation of fuel-wood exploitation to reduce the pressure on woodforest. Afforestation measures can also reverse the current trend of landuse/landcover conversions that affect hydrological processes in the River Kilange catchment.