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In recent years, unprecedented riparian vegetation exploitation for urban development in Nigerian cities
motivates this research. This study therefore assessed spatio-temporal changes of riparian vegetation and
associated environmental consequences in Osogbo city. Landsat TM 1986, Landsat ETM+ 2000, Landsat
OLI TIRS 2015 and a topographic map were utilized using GIS techniques. NDVI was carried out on the
images to detect temporal riparian vegetation degradation trend. Land use/land covers were extracted from
the images using supervised classification technique. 100m Buffers were created around river Osun within
the urban section to detect the magnitude of urban encroachment. Stochastic Markov and cellular automata
models were used to predict the level of riparian vegetation degradation in 2050.
The study found that NDVI values of the riparian vegetation showed dwindling mean values of 0.20, -0.05
and 0.17 in 1986, 2000 and 2015 respectively. Though, the pattern of land use/land cover change showed the
predominance of riparian vegetation (37%) over forest (31%), sparse vegetation (13%), built-up (9%), bare
ground (6%) and water body (4%) between 1986 and 2000 but the riparian vegetation receded at 2.63% per
annum over fourteen years and at rate of 1.9% per annum between 2000 and 2015 was observed.
Given the emerging pattern of land use/land cover change that revealed predominance of built-up (41%) over
other land use/land cover types {water body (5%), scattered cultivation (20%), shrubs and grassland (28%),
bare ground (1%) and riparian vegetation (5%) in 2015, the study predicts a worse condition for the riparian
vegetation by 2050 as most of the narrow strips of riparian vegetation observed along the river channels are
vulnerable to depletion and probably triggers serious flooding in Osogbo City. The study advocates
conscious implementation of land use zoning policy to conserve the fragile riparian vegetation and curtail
vulnerability of the city to flash floods.