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Abstract Hydrologic modeling using computer models has gained much attention in extreme flood event studies. Hydrologic Engineering Center Hydrologic Modelling System (HEC-HMS) is an extensively used software for streamflow generation in the hydrologic domain. This pilot study employs the HEC-HMS model in generating streamflows in the Chaliyar river basin, Kerala. Adequate representation of various water balance components of the hydrologic cycle is necessary for computing the surface and subsurface calculations. It is attained by combining appropriate sub-processes in the hydrological models. Remote sensing techniques integrated with Geographic Information Systems (GIS) are used in deriving the catchment characteristics. The simple canopy and surface methods are used to calculate the interception losses. The deficit-constant method is applied to estimate the infiltration losses, and the Clark unit hydrograph transforms the rainfall into runoff. The Muskingum method is used to route the reach segments within the watershed. Hydrometeorological data of the most influencing stations for the upstream Chaliyar basin are obtained by regionalization using the Thiessen polygon method. Daily precipitation data from four rain gauge stations, namely, Ambalavayal, Edakkara, Nilambur, and Manjeri, are used as the forcing inputs to the model. The streamflow data obtained from the Kuniyil gauge station is used to calibrate and validate the model. Various forecast skill scores like Probability of Detection (POD) and False Alarm Rate (FAR) are calculated from the categorical forecasts to quantify the forecast accuracy of the developed model. The model is used to simulate the intense flood event of 2019 in the Chaliyar basin.
Babu et al. (Sat,) studied this question.