Evaluation: Screening, Analysis, and Countermeasures for Bridge Scour for AL-Manshia Bridge

This paper aims to study scouring and the recommended countermeasures for Al Manshiya Bridge, which is located in the Blue Nile in Khartoum city. The bridge was constructed in the year 2006, but in 2015; the east embankment approach of the bridge was exposed to scour causing failure of the approach deck slab. The paper follows the general procedure outlined by the Federal Highway Administration (FHWA) for stream stability, evaluating scour at bridges and countermeasures in order to have hydraulically safe bridge. Geomorphic and hydraulic factors affect the stream were studied; a scour analysis was made using Hydrologic Engineering Center - River Analysis System (HEC-RAS) software. To account for long-term, contraction, and local scour potential for the Peak flow event, HEC RAS model was used to construct quasi- unsteady sediment model. In order to protect the bridge, countermeasures for the bridge east abutment and channel adjacent to the bridge are studied, riprap around abutment and spur dikes were considered as the most suitable countermeasures.