• K. BHASKAR
• P. MYNOR BABU

Large storage dams bring irrigation, drinking water and flood moderation, yet an uncontrolled release from them can devastate settlements lying downstream. This paper presents a hypothetical breach study of Somasila Dam, an earth-cum-masonry dam on the Penna (Pennar) River in SPSR Nellore district of Andhra Pradesh, carried out with the two-dimensional unsteady module of HEC-RAS. A terrain model built from a 30 m DEM, roughness values assigned from a 10 m land-use/land-cover map, and a reservoir elevation–volume curve were combined with the design flood hydrograph supplied by the state water resources department. The reservoir was assumed to stand at Full Reservoir Level (+100.58 m) with all spillway gates jammed shut. Breach geometry and formation time were derived from five regression approaches (Froehlich 2008, Froehlich 1995, Von Thun and Gillette, Xu and Zhang, and MacDonald and Langridge-Monopolis), and both overtopping and piping modes were run for each, giving ten simulations. Breach outflow peaked at about 97,649.44 m³/s for Froehlich (1995) under overtopping and at 76,355.35 m³/s for the same method under piping. At four reference locations downstream, maximum depths of 16.02 m (overtopping, MacDonald et al.) and 13.70 m (piping, Xu and Zhang) and maximum velocities of 3.45 m/s and 4.26 m/s were obtained, while the earliest arrival of the flood front was only 1.05 h after breaching. The outcomes show that the choice of breach-prediction method and failure mode alters depth, velocity and warning time appreciably, and the inundation maps identify ten villages, led by Somasila, Kammavaripalle and Uppalapadu, as the most exposed.

Dam break analysis, Somasila Dam, HEC-RAS 2D, breach parameters, overtopping, piping, inundation mapping

"DAM BREAK ANALYSIS OF SOMASILA DAM USING HEC-RAS", International Journal of Emerging Technologies and Innovative Research (www.jetir.org), ISSN:2349-5162, Vol.13, Issue 10, page no.b39-b45, October-2026, Available :http://www.jetir.org/papers/JETIR2610105.pdf

"DAM BREAK ANALYSIS OF SOMASILA DAM USING HEC-RAS", International Journal of Emerging Technologies and Innovative Research (www.jetir.org | UGC and issn Approved), ISSN:2349-5162, Vol.13, Issue 10, page no. ppb39-b45, October-2026, Available at : http://www.jetir.org/papers/JETIR2610105.pdf