Urban flash flood modelling based on merged rainfall satellite data - Application to Abidjan, Côte d’ Ivoire

Extreme rainfall events such as floods are most destructive with regard to their consequences on economics, infrastructures and humans as well as on ecosystems and wildlife. It is expected that weather extremes will become more and more frequent and more intense for many regions in the world. During the last decades, the metropolitan city of Abidjan (Côte d’Ivoire) has been under severe heavy storm events leading the World Bank in 2018 to rank the nation among the states most threatened by disasters due to global warming. The city has been flooded frequently during the last years with a lot of economic and human losses. In 2014, 23 persons died; in 2015, 16 persons died; in 2017, 15 persons died and in 2018, 17 persons died during the flood events as shown in Figure 1.

The expected changes in magnitude and patterns of extreme precipitation due to climate extremes impose the necessity to reevaluate the significance of extreme events.The aim of this research is to investigate the skill of hydrological and hydraulic model combination and merged satellite rainfall data in forecasting urban floods over a tropical catchment characterized by scarce ground-based observations. The framework will be based on bias-corrected merged satellite data and hydrological model (HEC-HMS) and a robust 2-D shallow water model (hms) under limited past storm events and post-event measurements. The research is applied to the urban catchment of the metropolitan city of Abidjan (Côte d’Ivoire).

The research should answer the following questions?

What are the differences between satellite-based rainfall estimates and rain gauge-based estimates in the city of Abidjan?

1. What is the appropriate correction scheme to reduce the bias and merge satellite-based rainfall estimates for hydrological and hydraulic model computation with scarce rain gauge data?  
2. What is the performance of the hydrological and hydraulic model combination in urban flood modelling using different sources of rainfall to delineate flash flood-prone areas?
3. What is the accuracy of different sources of rainfall in urban flood forecasting and early warning system development?
4. What are the adaptation measures which can be investigated for flood forecasting in the city of Abidjan?

The answers to these questions are the optimal way to overcome the challenges of the ungauged urban basins of Abidjan (Côte d’Ivoire).

Project head:

Prof. Dr.-Ing. R. Hinkelmann

Scientific assistant:

Gogous Habib Gogous, M.Sc.

Project period:

April 2020 – March 2023

Funding:

Institut National Polytechnic Felix Houphouet Boigny (INP-HB) of Cote d’Ivoire