Calibration of River Hydraulic Model Combined with GIS Analysis using Ground-Based Observation Data

In this research a method to calibrate a river hydraulic model (HEC-RAS) using ground-based measurements of an observed flash flood is presented. Applications of the ground truth measurement of flood water depths and flooded areas within a reach of Neka River in Northern of Iran are discussed. The model is calibrated using the Manning's roughness coefficient based on 200-year flood event that took place in this river basin in August 1999. The model performance with different sets of Manning roughness coefficients is compared to observed spatial inundation data. The comparison between observed and simulated flood water depths for the optimal values of Manning roughness coefficients has shown a significant correlation (p<0.0001, R = 0.82). Moreover, an agreement between the observed and simulated flood inundated extents is 88.5%. Floodplain inundation maps in different return periods were derived using integration of calibrated HEC-RAS model and GIS analysis. Delineation of flood extents and depths within the floodplain could be used for many practical applications.