Itzï

Digital elevation models (DEM) are fundamental for hydrologic and hydraulic modelling. Many practitioners rely on open‐access global data sets due to the cost and sparse coverage of sources of higher resolution. In 2016, the Japanese Aerospace Exploration Agency released the ALOS World 3D‐30m (AW3D30), an open‐access global elevation model at an horizontal resolution of 30 m. So far no published study has done an assessment of the flood modelling capabilities of this new product. The purpose of this investigation is to (a) assess the utility of the AW3D30 for flood modelling purposes and (b) compare its performance with regards to computed water levels and flood extent maps calculated using other freely available 30m DEM (e.g., SRTM and ASTER). For this comparison, the reference to reality is given by the maps computed using a light detection and ranging (LiDAR)‐based digital terrain model. This study is carried out in two catchments with contrasting topographic gradients. Results show that AW3D30 performs better than the SRTM. In mountainous regions, the results derived with the AW3D30 are comparable in skill to those obtained with a LiDAR‐derived digital surface model. This encouraging performance paves the way to more accurate modelling for both data‐scarce regions and global flood models.

The rainfall distribution is one of the most important factors that affects the watershed response to a given precipitation event. This paper uses radar rainfall to simulate of the floods of the city of Hull, U.K., in June 2007. The computed flooded areas from this rainfall and a uniform one is compared against those registered by public authorities. Results show similar skills at reproducing the real event, but differences appear in the total precipitated volumes, water depths and flooded areas. It is envisaged that in urban areas and with the advent of higher resolution radars, these differences will be more important and call for further investigation.

This paper presents Itzï, a new free software for the simulation of floods. It is integrated with a geographic information system (GIS), which reduces the human time necessary for preparing the entry data and analysing the results of the simulation. Itzï uses a simplified numerical scheme that permits to obtain results faster than with other types of models using more complex equations. In this article, Itzï is tested with three cases that show its suitability to simulate urban floods.

This paper presents a new hydrodynamic model named Itzï, designed to simulate surface flows in two dimensions by means of a pseudo-2D and partial acceleration numerical scheme on a raster grid. The model is implemented within GRASS GIS and is validated using two different analytic test cases for the full shallow water equations, and with the test 8a from the UK environment Agency.