Current Science

K. H. V. Durga Rao ¹, V. Venkateshwar Rao ¹, V. K. Dadhwal ¹, J. R. Sharma ¹, R. Jyothsna ¹

Affiliations
1 National Remote Sensing Centre, Indian Space Research Organisation, Balanagar, Hyderabad 500 037, IN

Abstract

This communication discusses quantifying basin-scale water wealth by transformation from the presently adapted basin terminal gauge site run-off aggregation to distributed hydrological modelling approach. In this study, an attempt was made to propose modifications to simple monthly water balance model using time-series land-use grids derived from the temporal remote sensing satellite data to compute run-off at basin scale. This approach will help in studying runoff and water resources availability with limited meteorological parameters. The study was aimed at computing mean annual water resources in the Godavari Basin, India during the last 18 years (1990-91 to 2007-08) using the proposed approach and to compute availability of water resources during extreme wet and dry rainfall conditions in the basin. The land-use grids were integrated with soil textural, digital elevation and command area grids to compute hydrological response unit grids. Groundwater, reservoir flux, domestic and livestock water consumption and industrial water consumptive use were computed using the spatial data and integrated in the model environment to compute run-off. The model was calibrated and validated using observed discharge data at various prominent gauge stations in the basin. Long-term water resources availability in the basin was computed using the developed methodology.

Keywords

Climate Change, Hydrological Modelling, Remote Sensing, Water Resources Availability.

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K. H. V. Durga Rao ¹, V. Venkateshwar Rao ¹, V. K. Dadhwal ¹, P. G. Diwakar ¹

Affiliations
1 National Remote Sensing Centre, Indian Space Research Organisation, Balanagar, Hyderabad 500 037, IN

Abstract

The recent floods in the Kedarnath area, Uttarakhand are a classic example of flash floods in the Mandakini River that devastated the country by killing thousands of people besides livestock. Though the duration of the event was small compared to other flood disasters in the country, it resulted in severe damage to property and life. Post-disaster satellite images depict that the river banks were eroded completely along the Kedarnath valley due to the flash floods and few new channels were visible. Extreme erosion took place in the upstream portion of Kedarnath, besides the breach of Chorabari Lake and deposition of debris/sediments in the valley. Hydrological and hydraulic simulation study was carried out in the Mandakini River using space-based inputs to quantify the causes of the flash floods and their impact. Chorabari Lake breach analysis was carried out using Froehlich theory. Flood inundation simulations were done using CARTO DEM of 10 m posting in which the combined effect of lake breach and high-intensity rainfall flood was examined. As the slopes are very steep in the upstream catchment area, lag-time of the peak flood was found to be less and washed-off the Kedarnath valley without any alert. The study reveals quantitative parameters of the disaster which was due to an integrated effect of high rainfall intensity, sudden breach of Chorabari Lake and very steep topography.

Keywords

Flash Floods, Flood Inundation Simulation, Hydrological Modelling, Lake Breach.

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K. H. V. Durga Rao ¹, A. Shravya ¹, V. Venkateshwar Rao ¹, V. K. Dadhwal ¹, P. G. Diwakar ¹

Affiliations
1 National Remote Sensing Centre, Indian Space Research Organisation, 500 037, IN

Abstract

The recent flood in Machak River, Madhya Pradesh, India is a distinctive paradigm of flash floods that washed off rail tracks and killed a number of passengers besides incredible damage to Indian Railways and to the surrounding villages. This shows the vulnerability of bridges/culverts to flash floods in the country. Flash floods devastated the Machak River during the midnight of 4 August 2015 due to heavy rainfall in the catchment. The duration of flooding was small with less lead-time. Narrow river sections could not accommodate the peak discharge causing severe flooding in floodplains. Hydrological and hydro dynamic simulation was studied in the Machak River using space-based inputs to quantify the causes of flash floods and its impact. Satellite-based rainfall (GPM and IMD's WRF merged product) was used in hydrological modelling in the absence of field rainfall and discharge data. Flood inundation simulations were done using CARTO digital elevation model of 10 m resolution. Inundation extent, depth of inundation, and velocity of flow at different reaches were examined. As the slopes were steep in the upstream catchment area, the lag-time of the peak flood was found to be less and washed off the Machak rail culvert without any alert. The study reveals that quantitative parameters of the disaster are due to high intensity of rainfall, drainage congestion and sudden change of slopes across the catchment.

Keywords

Hydrological Simulation, Hydrodynamic Modeling, Machak River, Rail Accident.

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