ANNOUNCEMENTS
The study looks into the floods that occurred in Kerala in August 2018 from a hydrology point of view with the assistance of GIS. In order to assess the river basin, Flood modelling was carried out using Hydrological modelling followed by Hydraulic modelling. The Hydrological modelling was performed using the software HEC-HMS, generally used for semi-distributed systems, to generate runoff at each element of the catchment from the precipitation gage data and other hydro-meteorological variables. The values of all the parameters required for the flood modelling were determined by calibrating and validating the model after a sensitivity analysis followed by a simulation of the extreme event. Flood Frequency analysis was performed, using 30 years past discharge data generated in HEC-HMS, in order to determine peak discharge values for different return periods using 3 distribution methods – Gumbel, GEV and Log Pearson Type III. 1-D Hydraulic modelling was performed on the discharge data generated for the extreme event in HEC-HMS, through Unsteady flow analysis, and on peak discharge values generated through Flood Frequency analysis via Steady flow analysis in HEC-RAS. Flood inundation maps were generated, which showed the inundation of a large part of the floodplains comprising of urban and agricultural area. A Flood Vulnerability analysis was performed for the floodplain of the river which showed that with increasing return periods, the inundation would also increase thus increasing the vulnerability of the urban and agricultural areas especially, unless existing practices change.
Keywords: Flood Frequency Analysis, Flood modelling, GEV, GIS, Gumbel, Hydrological Modelling, Hydraulic Modelling, HEC-HMS, HEC-RAS, Inundation mapping, Log Pearson Type III
