Watershed delineation and cross-section extraction from DEM for flood modelling

Hydrological and hydrodynamic models are the practical tool for flood modelling. Watershed delineation is a prime step for hydrological model development. Two types of delineation techniques; manual and automatic are available. Manual watershed delineation is far more difficult and time consuming than automatic delineation. On the other hand, river cross-sections are the most important input to any river hydrodynamic model. Measured cross-sections are scarce in most of the large river basin or catchment. Field survey is very expensive and labour intensive to get the measured cross-section. Therefore, automatic cross-section extraction from Digital Elevation Model (DEM) is the easiest and cheapest option. Nowadays due to availability of DEM worldwide and several software packages, automatic delineation of catchment and automatic extraction of cross-section have become very popular. In this paper, watershed delineation and cross-section extraction from DEM for lower Fitzroy river basin are presented. Besides, the usefulness of using the watershed delineation and cross-section extraction from DEM under the scarcity of watershed information and measured cross-section data are demonstrated and discussed.