Rivers constitute an important focus of attention in surface water studies because of their dynamic nature. Therefore, natural rivers develop a wide range of channel forms whose characteristics vary as a function of the position within the fluvial systems. This study examined the river channel morphologic parameters along the alluvial section of River Ogun in South western Nigeria. Data on the channel morphologic variables were collected through field measurement of the bankfull cross sectional characteristics of the river from where the longitudinal characteristics were defined. 48 cross sections were randomly established at bankfull stage along the river channel stretch of 90 km. Bankfull depth and width at each of the cross sections were determined using sonar (electronic sounding machine) that was mounted to a boat. Velocity was measured with the aid of a current meter, while other morphological parameters were estimated from the field data. Analysis of variance revealed that downstream morphological characteristics of the river varies distinctively at each cross section with bedslope as the most significantly varied among all other morphologic parameters (F=91.18; P=0.00). Pearson product moment correlation technique revealed that bankfull width had a correlation of 0.8 and 0.9 with wetted perimeter and cross sectional area respectively while bankfull depth (maximum) had correlations of 0.9, 0.8 and 0.78 with hydraulic radius, wetted perimeter and cross sectional area respectively. The research also revealed that gradient affects the discharge with a positive correlation of 0.9. The study ascertains the extent of variability in the morphologic characteristic of River Ogun which provides scientific basis for river maintenance and management.
The term region has its origin in geographical studies and refers to a more or less defined portion of the earth's surface distinguished either by natural features (e.g., climate, vegetation, landform) man-made features (e.g., settlement and other forms of landuse), or both. The main characteristic of either type of region is functional unity and relative homogeneity, which together minimize effort, whether in terms of the natural processes or the amelioration and control of these processes for purposes of development.
The River Continuum Concept (RCC) is an existing theory regarding the distribution of plant communities along riverbanks. This study is concerned with the pattern of riparian vegetation along the Lower Ogun River (LOR) in relation to the observed downstream variation of various environmental factors (bank height, width, gradient, distance, cross‐sectional area and particle size). The LOR transits between undisturbed and disturbed sections. Forty‐eight cross sections were established at bankfull stage along the river channel stretch of about 90 km. Environmental variables distribution were determined using standard field procedures. Gradient was estimated from a 1:50 000 topographical map. At each corridor along the study sites, a 0.1 ha sampling site was chosen, in which 10 transects of 100 m2 were demarcated. In all, 332 individuals stratified under 80 species were recorded across the transects. The study revealed that total species richness (TSR) downstream decreases exponentially. TSR is significantly correlated with channel width, suggesting that hydraulic variable contributes more to the variation in TSR. The downstream total environmental factors revealed that width is inversely significant with downstream distance, suggesting that the river channel is narrower downstream. This affects plant life form distribution downstream and confirms why there is appearance of anthropogenic induced species downstream as against those in the upper course.
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