Real Time Flood Forecasting - Indian Experiences

The real time flood forecasting is one of the most effective nonstructural measures for flood management. For formulating the flood forecast in the real time, the observed meteorological and flow data are transmitted to the forecasting station through the different means of data communication which include telephone, wireless and network of telemetry stations etc. The collected meteorological and flow data in real time are then used into the calibrated & validated real time flood forecasting model to forecast the flood flow and corresponding water levels for different lead periods varying from few hours to few days depending on the size of catchment and purpose of the forecast. The structure of the model should be simple and it should not have excessive input requirements, but at the same time the forecasted flood must be as accurate as possible. Different types of real time flood forecasting techniques and models have been suggested and used by many investigators. These can be broadly classified into (i) deterministic models, (ii) stochastic and statistical models and more recently (iii) Artificial Neural Network (ANN) and fuzzy logic techniques. In India the various flood forecasting centers are using different forecasting models, based on the availability of hydrological and hydro-meteorological data, basin characteristic, computational facilities available at the forecasting stations, warning time required and purpose of forecast. Some of the commonly used methods by various forecasting stations include: (i) simple correlation based on stage-discharge data, (ii) co-axial correlation based on stage, discharge and rainfall data etc, (iii) net work model wherein the lateral flows from different sub-basins are calculated using unit hydrograph approach and successive routing through different sub-reaches is carried out using river flood routing techniques, and (iv) hydrologic models (at selected places). The recent techniques like ANN and fuzzy logic are being currently used by the academicians and researchers for the development and testing. In this lecture brief description of various real time flood forecasting models and techniques being used in India are presented. The limitations of the techniques are discussed. The status of the real time flood forecasting in India including those of the arid and semi-arid basins is presented. The present gaps in the application of real time flood forecasting techniques in India are highlighted. ________________________________________________________________________ * Scientist F, National Institute of Hydrology, Roorkee247 667, India