Gelareh Farahi - Irrigation Department, Agriculture Faculty, Ferdowsi University of Mashhad, Mashhad, Iran
Vahid Tayefi - Geographic Department, Tarbiat Modares University, Tehran, Iran

An understanding of floodplain processes in general and floodplain flooding and inundation in particular are vital issues for river engineers and managers. Insufficient observations of flood inundation extent and the infrequent nature of flood inundation necessitate some sort of predictive tools. In response to this, flood inundation extent models using hydrodynamic models ranging in complexity from a simple planar approximation (i.e. 1D such as MIKE11, ISIS, ONDA, FLUCOMP and HEC-RAS) through to fully 2D (such as MIKE21, TELEMAC, RMA2 and hydro2de) and 3D (3D-ELCOM) hydrodynamic models have been developed and applied. To date, hydrodynamic models used for flood modelling can, at best, be divided into one-dimensional models in normal mode, one-dimensional models in storage cell mode, quasi (i.e. diffusion wave treatment or raster-based models), full two-dimensional models and two-dimensional models The first part of this paper intends (i) to address the hydraulic principles in two simple three-dimensional 1D hydrolic models called hec-ras in normal mode and hec-ras in storage cell mode simple 1D model, (ii) to review capabilities and limitations involved in model parameterisation particularly in relation to topographic data for each model (iii) to compare the calibration and validation of such models.

Hydrodynamic models, Inundation extent, Floodplain hec-ras in normal mode, hec-ras in storage cell mode