Two dimensional dam break analysis of ichari dam using HEC-RAS
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Date
2018-06
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
Construction of a dam serves multi benefits to the society, with all these multi benefits, a failure of dam structure can cause tremendous loss of life and property. In order to reduce the threats due to dam failure, dam break analysis become necessary to predict flood inundation levels, time of arrival of flood, velocity of flood and extent of flooding in downstream areas of dam. The information obtained from dam break analysis can be used by local authorities and owners of dam in preparing Emergency Action Plan (EAP) and designing early warning system. Present study deals with two dimensional unsteady flow simulation of hypothetical failure of Ichari dam using HEC RAS software in both rainy day and sunny day scenario. The main objective of the study are to determine breach parameters, flood hydrograph, time of arrival of flood, velocity of flood and depth of flood wave at selected locations and to determine the extent of flooding in the downstream of dam. HEC RAS is a freeware software and is one of the most comprehensive and popular hydraulic model used for dam break analysis. HEC RAS is a parametric hydraulic model that estimate peak discharge and breach hydrographs based on parameters provided by user. Ichari dam is built on Tons river in Dehradun district of Uttarakhand having Latitude of 30°33_23_N and Longitude 77°47_53_E respectively. It is a concrete gravity dam of height 59.25 m and 155 m length. The study concludes that Maximum Water Surface Elevation among both scenarios obtained at Dakpathar, Vikasnagar, and Paonta Sahib which are in close proximity of river Tons in downstream side of Ichari dam are 429.8 m, 407.18 m and 363.83 m respectively and therefore people living very close to dam site need to build their houses above this level. In extreme case of flooding that is maximum breaching of dam at full reservoir level and with full Inflow Design Flood, the extent flooding is limited to floodplains. The flood inundation maps obtained from this study will be very helpful in floodplain zoning and regulating developmental activities in floodplains by the local authority.
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