Solution to the Breach of the Dike of Keur Bara KAIRE, Located in the Commune of Notto Diobasse in the Department of Thiès, Senegal

Abstract

This article studies the rupture of the Keur Bara KAIRE dike, located in the commune of Notto Diobasse in the department of Thiès in Senegal. The village is crossed by a stream which collects rainwater from the west to the east, following a natural slope. The overflow of this stream causes serious flooding, leading to the total cutting of the road and the isolation of the population. These floods had tragic consequences, resulting in two losses of human life. To regulate the water level, prevent flooding and protect agricultural and urban areas from overflows, the Senegalese authorities initiated the project to build the Keur Bara KAIRE dike in 2004, unfortunately the latter gave way in 2017. The geotechnical analysis was carried out on samples taken from various points on the site, revealing that the terrain is mainly composed of fine sand and the embankment is made with clayey sand. Morphometric and hydrological investigations highlight that the watershed of the Keur Bara KAIRE dike covers an area of 3.72 km², with a projected flow of 54.99 m³/s. The resizing of the dike revealed the following data: a length of 132 meters and a height of 3 meters. The spillway is 52.99 meters long with a reservoir height of 1.22 meters. The bay walls have a thickness of 50 cm and the embankments have a slope of ½ upstream and downstream. The stability calculation on the broken dike reveals a sliding safety factor (FSG) of 1.84 which complies with the standard and an overturning safety factor (FSR) of 0.13 which is not verified. The surface of the watershed which is equal to 3.72 km², also the smallest height of precipitation is equal to 234.9 mm and the largest 664.4 mm, the ORSTOM and CIEH methods for hydraulic calculations.