Assessment and Design of Suitable Flood protection work at the Downstream of Gereb Burka River, Southern Tigray

Abstract

Flooding along the downstream section of the Gereb Burka River in Southern Tigray's Raya Azebo Wereda near Mekoni city poses significant risks to communities and infrastructure. This study proposes flood defense measures to mitigate these hazards through gabion structural interventions. Hydrological analysis was conducted using rainfall data from the Maichew meteorological station (1993–2019), applying methods for missing data estimation, adequacy testing, and outlier detection. The Soil Conservation Service Curve Number (SCS-CN) method was employed to estimate runoff, considering land use/land cover and hydrologic soil groups (CN = 86 for AMC III). Peak discharge was calculated as 234.5 m³/s for a 25-year return period, with a probable maximum rainfall of 80 mm derived from log-normal distribution analysis. Gabion structures were identified as the most suitable flood defense mechanism due to their cost effectiveness, adaptability, and compatibility with the erosion-prone, semi-arid conditions of the region. A detailed stability analysis confirmed the structural integrity of the proposed gabion design, with factors of safety against overturning (>4.1), sliding (>1.6), and bearing capacity failure (>7.6) meeting engineering standards. The design includes a 2.2 m-high gabion wall with a 73 m waterway width. This research provides a practical solution for flood mitigation in the study area and serves as a reference for similar projects. Recommendations emphasize regular maintenance of flood defenses, community awareness programs, watershed reforestation, and further studies on sediment management to enhance long-term resilience. The project underscores the importance of integrating hydrological and geotechnical analyses in flood protection planning.