Author(s): Mysooru R. Yadupathi Putty; A. M. Aniruddha; N. Pandu; Sanjay Kumar; Vijay Pujar; C. Siddaraju; M. Lohith
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Keywords: The unit hydrograph; CWC method for flood estimation; Variable source area regions; Inapplicability of classical methods
Abstract: Despite evidences to the contrary, the premise that the catchment topographic characteristics shape the flood hydrograph continues to dominate the thought in Hydrology. Hence, the Unit Hydrograph (UHG) Method is still being used for flood estimation even in areas where overland flow is not widespread. The Central Water Commission in India (CWC) too advocates this method, and has published handbooks for flood estimation across the country. The applicability of this standard method has gone unchecked in most areas due to lack of continuously recorded streamflow data. The aim of the present work has been to study the fairness of the CWC model for application in the highly wet Western Ghat areas of Karnataka, by using continuously recorded discharge data in a typical very small catchment in the state of Karnataka in India. The work has been accomplished by developing 1-hour UHGs from a number of flood events and comparing them with the one obtained using the CWC guidelines. Having found that the shape of the field hydrographs differ much from the‘synthetic UHG’, an explanation has been sought for the failure of this commonly used method. It is found that the predominance of the delayed flow, commonly called‘baseflow’in classical hydrology, is the reason. It is argued that there is a need for a thorough new look at the methods for flood estimation in this region.
Year: 2016