Country – Ethiopia
Context of risk assessment
The Borana region, which is located in an arid area, faces increasingly frequent and intense extreme weather events such as floods and droughts. Heavily dependent on water resources for agriculture, livestock and the needs of local populations, it is among the most vulnerable to the impacts of climate change.
With an average water availability of 1,109 m3 per capita per year, Ethiopia is in a situation of water stress, and some southern regions have less than 500 m3 per capita, accentuating the precariousness of communities.
In addition, heavy rain and flooding degrade water quality, increasing the risk of source contamination and disease spread. The lack of adequate infrastructure, combined with population pressure and limited resource management, highlights the urgency of conducting forward-looking studies on water and climate change.
Objective of climate and flood risk assessment in the Borana region
The assessment of climate change risks in the Borana region focuses mainly on the analysis of hydrological impacts and flood risks. The aim of this project is to provide scientific data and decision-making tools to local and regional stakeholders, in order to anticipate and manage the effects of climate change on water resources and populations. By integrating a chain of impact models, a detailed analysis of flood risks and a mapping of future risks, this study is part of our specialized services:
Phase 1: Setting up a chain of impact models
The first step in this risk assessment is to deploy a chain of hydrological and climatic impact models adapted to the Borana region. These models will simulate changes in precipitation, temperature and river flow as a function of climate change scenarios.
The specificity of this phase is based on 3 pillars:
- Fine and territorial moedeling: taking into account local physical and hydrological characteristics such as soil types, relief and land use.
- Integration of regional climate data: projections from global climate models are refined to obtain results tailored to Borana.
- The generation of key hydrological data: including precipitation levels, groundwater recharge, and river flows, to identify future trends in the context of climate change.
These impact models provide the necessary foundations for the following phases, establishing a clear understanding of future conditions in the region and their implications for hydrological risks. They provide a solid basis for risk assessment.
Phase 2: Flood risk analysis in the context of climate change
The second phase of flood risk mapping is based on the use of a 2D digital hydraulic model, coupled with regionalized hydroclimatic projections. This approach simulates the spatial extent of floods and accurately identifies the most vulnerable areas according to different flood scenarios.
1) 2D hydraulic model: a realistic simulation of flows
Unlike the 1D models, which only take into account the longitudinal flow in a hydrographic system, the 2D model simulates in more detail the dynamics of flood water propagation on flood surfaces. It includes:
- Detailed terrain topography (high-resolution NTM), essential to represent runoff and stagnation zones.
- The characteristics of watercourses and hydraulic structures (dams, dams, bridges, etc.) that influence runoff.
- Roughness coefficients related to land use (urban areas, forests, crops) to estimate the speed and depth of water during a flood event.
Using these elements, the model accurately reproduces flood dynamics, including overflows, flow velocity and water heights at each point in the studied territory, which facilitates the assessment of the risks associated with these events.
2) Linkage with regionalized hydro-climatic projections
One of the major challenges in assessing risk, and more specifically flood risk in the context of climate change is to integrate future changes in climate and hydrology. The 2D hydraulic model is therefore fed by regionalized hydroclimatic projections from phase 1, allowing to analyze how future floods could evolve under different climate scenarios.
Phase 3: Future flood risk mapping and technical report
The final phase of this risk assessment is to translate the results of the analyses into actionable decision-making tools. Dynamic flood maps are generated by integrating future climatic conditions and associated uncertainties. These maps highlight the areas most vulnerable to flooding, thus identifying priorities for land use planning and water resource management.
Each map is accompanied by a detailed technical report, including:
- The results of climatic and hydrological analyses.
- Flood risk projections for different climate scenarios.
- Strategic recommendations to reduce risks and strengthen adaptation to climate change.
Integrating this risk assessment analysis into risk management plans, while helping local actors to strengthen existing infrastructure and adopt more resilient adaptation strategies.
Why is this evaluation essential for Borana?
The Borana region is facing increasingly frequent extreme weather events, including floods and droughts, threatening infrastructure, agriculture and local populations.
The main benefits of this risk assessment are :
- A better understanding of climatic hazards through models adapted to the region.
- Anticipating future impacts by identifying the most vulnerable areas.
- Decision support for local actors to guide investments and strengthen the resilience of the territory.
This risk assessment provides a comprehensive and tailored vision to address the challenges posed by climate change in the Borana region.
Conclusion
The Borana region illustrates the growing challenges of climate change in arid areas where water is becoming a critical and vulnerable resource. The intensification of droughts, changes in rainfall patterns and deterioration in water quality increase the vulnerability of local populations, which are highly dependent on water resources for agriculture and livestock.
In response to these challenges, strengthening adaptation strategies relies on risk assessment and accurate data. Optimized management of water resources, coupled with appropriate infrastructure and resilient practices, is an essential response to mitigate the impacts of climate change and ensure the sustainability of local activities. This study highlights the need for an integrated approach to preserve infrastructure, ecosystems and people’s living conditions.