The study applies advanced models of design storm like Flood Analysis and Protection Systems (FLAPS) and HEC-1 for rainfall-runoff simulation employing selected short-term events of three basins of the north-eastern region – Myntdu-Leska (Meghalaya), Krishnai and Dudhnai (Assam). The results are used to study the sensitivity of the model parameters with respect to different hydrological parameters of the basin. The performance of these methods is evaluated by analyzing the isolated events. An attempt has been made to evaluate the non-linearity in rainfall-runoff response, using a simple storage-runoff dynamic model. The relationship of incipient soil moisture and transmissivity with direct runoff and recharge is studied.
Advanced methods of design storm estimation, unit hydrograph derivation, flood frequency analysis and other distributed models for rainfall-runoff simulations have been developed in recent times. In this study a conceptual distributed hydrological catchment model, FLAPS is compared with HEC-1 in simulating the rainfall-runoff processes for selected events. Through the established rainfall-runoff relationships and calibrated model parameters, the results are meant to be a design tool where historical design storms with a certain recurrence can be analyzed in terms of runoff.
The model has the flexibility to treat the study area either as a linked system of a number of sub-basins or as a lumped system, which has parameters corresponding to its physiological conditions. In linked systems, sub-basins are connected separately either by river reaches, channels or lakes represented by corresponding routines. The estimated runoff is used with the actual runoffs for calibrating model parameters, which are used in some test events to check the validity of the parameters of the basin. The time of concentration and storage constant of a basin are optimized using HEC-1 and the parameters are validated for a storm. The parameters thus obtained are used in the model to arrive at a unit hydrograph for the basin.
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