Hydraulic roughness of periwinkle shell and Rapana venosa gabions to assess their viability for hydraulic engineering applications

This study assesses the hydraulic roughness of periwinkle shell and Rapana venosa gabions to ascertain their appropriateness for hydraulic engineering applications. Laboratory tests were performed utilizing a rectangular flume (0.6 m wide, 0.45 m deep, and 5.0 m long) in the Niger Delta region, where periwinkle shells are prevalent. Flow discharges between 0.015 and 0.045 m³/s were introduced, with matching measurements taken for velocity, flow depth, and hydraulic radius. The Manning's roughness coefficient (n) and the Darcy–Weisbach friction factor (f) was calculated from the observed data. The findings indicated that periwinkle shell gabions exhibited elevated roughness values, with Manning’s n varying from 0.034 to 0.041 and the friction factor f ranging from 0.045 to 0.052. Conversely, Rapana venosa gabions had reduced values, with n varying from 0.028 to 0.033 and f between 0.038 and 0.044. The findings demonstrate that periwinkle shells offer enhanced flow resistance and energy dissipation, rendering them effective for erosion-prone channels and flood control systems. In contrast, Rapana venosa gabions demonstrated more favorable flow conditions, appropriate for irrigation canals and conveyance systems. The study indicates that shell-based gabions offer a cost-efficient and sustainable alternative to traditional aggregates, facilitating waste reutilization in hydraulic infrastructure.