MDTanaliza: understanding digital elevation models when facing gravity-driven flows in a hazard assessment context

The Digital Elevation Model (DEM) is one of the most important inputs when working on computer simulations to define areas potentially affected by gravity-driven flow hazards. Sometimes there is only one DEM available in the study area, although nowadays the availability of several different DEMs of varying resolutions and precision is more frequent, the characteristics of which are not necessarily familiar for the users. This availability may increase during emergency events in high-risk areas where updated and more precise DEMs may be calculated every few months using less expensive and more advanced methods. In order to design gravity-driven flow hazard maps, it is critical to understand the changes that may be taking place in computer simulations that use various DEMs to get a general understanding, for example, of the drainage network representation or how resolution changes may make the flow paths differ and how this may affect the interpretation of existing hazard maps that may be enhanced with the new DEM and cartography-base maps. To support researchers in these tasks, a simple and flexible ANSI C software tool called MDTanaliza has been developed. The aim of this tool is to analyze all possible gravity-driven flow paths, recreating former or new morphologies and calculating various different basic morphometric parameters in order to understand and compare the DEMs available in a study area. We have also developed some innovative approaches to improve the gravity-driven flow path analysis: the Filling Depression function to work with non-depressionless DEM and to reduce the time computing; the Pathway Force Interaction function that allows the previous gravity-driven flow paths to be considered in the next path calculation; and the Restricted Multiflow function to control the dispersion in the Multi-Directional flow model. As an example, the summit area of the Cotopaxi volcano has been used.