AN APPRAISAL AND DESIGN OF SURFACE WATER DRAINAGE IN BIDA (A CASE STUDY OF AREA 7 JUNCTION TO POLY JUNCTION)

Urban flooding and erosion caused by inadequate drainage remain pressing infrastructural challenges in Nigerian cities and towns. This study focuses on an appraisal and design of surface water drainage along Area 7 Junction to Poly Junction in Bida Local Government Area, Niger State. The research aimed to evaluate the existing drainage condition, identify deficiencies, and propose a technically sound and economically viable solution to manage stormwater within the corridor. A comprehensive field survey involving physical inspection, GPS mapping, and community interaction revealed that over 35% of the 1.5 km corridor lacks formal drains, while many existing sections are clogged, silted, or poorly graded. Hydrological analysis using the Rational Method with a 5-year return period rainfall intensity (90 mm/hr) and a weighted runoff coefficient (C = 0.70) produced a peak discharge of 1.015 m³/s. Hydraulic design using Manning’s equation resulted in a trapezoidal concrete channel with a bottom width of 0.4 m, depth of 0.6 m, side slope ratio of 1:1, and a longitudinal slope of 1.8%, sufficient to carry the peak runoff with freeboard. The proposed design incorporates catchpits at 50 m intervals, reinforced precast slab covers for safety, and erosion-resistant concrete lining to ensure durability. A bill of quantities estimated the project cost at approximately ₦7.47 million, based on prevailing rates from the Niger State Ministry of Works and Housing. Community feedback indicated widespread support for the intervention, particularly in reducing flooding, improving road accessibility, and enhancing public health conditions. The study concludes that the implementation of the proposed drainage system will significantly mitigate flooding, improve environmental quality, and extend the lifespan of adjoining road infrastructure. It recommends routine maintenance of drains, enforcement of urban planning regulations, and public sensitization against indiscriminate waste disposal. Furthermore, this project contributes to sustainable urban drainage design by providing a location-specific model that can be replicated in other parts of Bida and similar Nigerian towns.