Free Global DEMs and Flood Modelling—A Comparison Analysis for the January 2015 Flooding Event in Mocuba City (Mozambique)

Julio Garrote

doi:10.3390/w14020176

Abstract

Flood hazard and risk analysis in developing countries is a difficult task due to the absence or scarce availability of flow data and digital elevation models (DEMs) with the necessary quality. Up to eight DEMs (ALOS Palsar, Aster GDEM, Bare Earth DEM, SRTM DEM, Merit DEM, TanDEM-X DEM, NASA DEM, and Copernicus DEM) of different data acquisition, spatial resolution, and data processing were used to reconstruct the January 2015 flood event. The systematic flow rate record from the Mocuba city gauge station as well as international aid organisms and field data were used to define both the return period peak flows in years for different flood frequencies (Tyear) and the January 2015 flooding event peak flow. Both visual and statistical analysis of flow depth values at control point locations give us a measure of the different hydraulic modelling performance. The results related to the Copernicus DEM, both in visual and statistical approach, show a clear improvement over the results of the other free global DEMs. Under the assumption that Copernicus DEM provides the best results, a flood hazard analysis was carried out, its results being in agreement with previous data of the effects of the January 2015 flooding event in the Mocuba District. All these results highlight the step forward that Copernicus DEM represents for flood hazard analysis in developing countries, along with the use of so-called “citizen science” in the form of flooding evidence field data acquisition.

Highlights

Floods, in any of their typologies, are probably the most frequently recurring natural phenomenon affecting global society, regardless of their geographical location or socioeconomic development, as shown by the data collected by the International Disasters Database for the period 1900–2020 [1]
The choice of Mocuba city was due upon two main criteria: the city belongs to a developing country and there is a repeated occurrence of flood events
This trend of results is less evident for TanDEM-X and MERIT digital elevation models (DEMs), and it is totally unrecognizable for the rest of the models, where the variations in flow depth cannot be due to the natural forms of the channel but to the presence of topographic errors

Summary

Introduction

In any of their typologies, are probably the most frequently recurring natural phenomenon affecting global society, regardless of their geographical location or socioeconomic development, as shown by the data collected by the International Disasters Database for the period 1900–2020 [1]. This international database collects 11,356 records of hydrological and meteorological events around the world for the time period between 1900 and 2020, with totals of 8.6 million deaths and 2600 million US dollars (2019) of economic damage. We must bear in mind the results of Hallegatte et al [2], who estimated that global flood losses by 2050 would amount to a total of USD 1 trillion

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Conclusion