Riparian health conditions of headwater streams in Southwestern Nigeria

Abstract

ABSTRACT River health assessments and threat analysis on the riparian corridors in Sub-Saharan Africa have received little or no attention, therefore this study assessed the healthiness of riparian corridors using the Rapid Appraisal of Riparian Condition (RARC) indices within a river catchment. The biogeography of the riparian corridor, factors responsible for the modification of riparian vegetation, and causes of riparian disturbance were examined. Twelve study sites were randomly selected from where reaches were identified. The riparian corridor extents were delimited from the bank of the river to the uppermost point within reaches. Species diversity indices were computed while bank height, width, and average depth were measured. Also, cross-sectional area and river discharge were derived along each riparian zone using standard measurement techniques. The ecological values and threat severity along each riparian zone were assessed following the RARC model. The ecological values and disturbance level revealed r as −0.7(p < 0.05). The variation in species composition along the river orders suggests that the first-order streams have the highest number of taxa. The level of ecological destruction is fairly low in the first-order streams and increases as order increases. This study concludes that higher-order rivers have low diversity, low ecological values, and consequently, relatively poor health, especially when under severe anthropogenic pressure.