Flash Flood Disaster Threat to Indian Rail Bridges:A Spatial Simulation Study of Machak River Flood, Madhya Pradesh

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.