ANALYSIS OF DAM BREACH PARAMETERS AND INUNDATION MAPPING (THE CASE OF KALID-DIJO EMBANCKMENT DAM)

Abstract

Embankment dam risk assessment is a method used to evaluate the catastrophic impact of dam break flooding. This study was conducted to analyze dam breach parameters of Kalid Dijo dam and inundation mapping. The dam breaching outflow hydrographs, inundation mapping and downstream flood propagations were simulated by applying HEC-RAS 5.0.6 model to study the possible relationships among the peak flows, dam breach parameters, and map the inundation area. The initial parameters are taken from literature based on the dam type and its silent features. HEC-RAS model 2D reservoir and river routing were performed and resulted in multiple breaching outflow hydrographs for specified conditions at the dam site and at specified downstream reach stations. The maximum breach discharge resulted from the model was 852.18 m3 /sec which results in overtopping the dam by 0.6m. Four Time to Failure Hour and four Breach Side Slope values are used for the sensitivity analysis at the dam site. Accordingly, the change of Time to Failure Hour resulted 403% change of the maximum discharge at the dam site which is high compared to the change in Breach Side Slope which produced 100% reduction in maximum discharge. This implied that the peak discharge was highly sensitive to changes in Time to Failure Hour more than five times than Breach Side Slope; and Time to Failure Hour is a controlling parameter at the dam site. At two randomly selected downstream observation stations 01 and 02, an increase in TFH and increase in Manning coefficient resulted in decrease in peak flow at reach station-01 and 02. The total inundated area is 454.19 sq.km. It covers 1100ha of command area and some parts of Dalocha town.