New Hazard Exposure Model for Africa

Earthquakes, landslides, volcanoes, droughts, floods, and storms have all struck Africa in the past half century, affecting half a billion people through deaths, displacement, and economic losses. Now, researchers have proposed a new disaster exposure model for the continent that could be used to conduct risk assessment for a variety of natural hazards.

The Global Earthquake Model (GEM) Foundation in Pavia, Italy, featured in Eos last year, led an effort to develop an open seismic hazard and exposure model for the continent in collaboration with AfricaArray, a public-private partnership supporting training and research in Earth, atmospheric, and space sciences in Africa.

The group went on to develop a more comprehensive exposure model for all natural hazards and recently published a paper about it in the International Journal of Disaster Risk Reduction.

Risks of Rapid Urbanization

Disaster risk is an increasingly relevant issue for cities around the world, said Nicole Paul, a seismic risk modeler at GEM and lead author of the new study. Logistics and diverse demographics can make disaster response complex, and risk modeling must incorporate those factors.

Cities provide economic opportunities, but rapid growth can pose challenges to ensuring adequate infrastructure and housing. In locations where urban planning fails to keep pace, slums and overcrowded communities are likely to proliferate. Overcrowded communities are often accompanied by a higher vulnerability to damage, losses, and displacement following natural hazards, Paul explained.

Africa is home to some of the world’s fastest-growing urban areas, including the megacities of Kinshasa, Democratic Republic of the Congo, and Lagos, Nigeria, both of which have populations of more than 15 million. The continent also has almost 2 dozen cities with populations between 1 million and 2 million.

Many of these growing cities, like Addis Ababa, Ethiopia; Bujumbura, Burundi; and Lilongwe, Malawi, are exposed to moderately high seismicity given their proximity to the East African Rift System.

These cities are made vulnerable by “development in hazard-prone areas such as in floodplains, [as well as by] poor drainage management systems, or a lack of building code enforcement that would otherwise mitigate damage due to hazards such as earthquakes and fires,” Paul said.

Developing the Model

Modeling disaster risk in Africa and investing in disaster response planning is crucial, said Paul and her colleagues at GEM. “Investments and planning decisions made in the near term will shape disaster risk experienced by current and future residents of African cities, a population estimated to reach 1.3 billion by 2050,” she said.

More sophisticated risk modeling is especially relevant, with countries such as Angola, Niger, Somalia, and Tanzania anticipated to double their number of buildings by 2050, according to the new research.

“We are fortunate in Africa to have this model….To put together all of the data sets for such a large continent can be a mammoth task.”

“That’s a lot of buildings still to be built in the next few years and a massive opportunity to reduce future disaster risk through risk-informed design and planning,” said Paul. Risk-informed plans or mitigations include creating building codes where they don’t exist, removal of debris from drainage systems, and upgrading informal settlement infrastructure.

The exposure model covers residential, commercial, and industrial buildings in Africa through 2050. The inclusion of all buildings is a key asset of the new model, said Brian Mubiwa, assistant program manager at the United Nations Environment Programme–South Africa who is not involved in the study. “This new model highlights the potential impact on such important assets as the commercial and industrial building stock, which are often overlooked, as existing models tend to shine the spotlight on residential building stock,” he said.

“We are fortunate in Africa to have this model.…To put together all of the data sets for such a large continent can be a mammoth task,” said Mayshree Singh, director at Maya Geophysics, a South African seismic hazard consulting service. Singh was not involved in the study.

Another “bonus” in the new model “is that the data sets and hazards are presented quantitatively using a unified, well-established modern approach that is also used internationally, so researchers in Africa can now build on this study and particularly improve on areas where there are gaps in the data sets,” Singh said.

“Funny enough, some traditionally built houses perform better during…earthquake shaking.”

Incorporating data on construction typology (e.g., low-rise adobe masonry or high-rise steel towers) is particularly important in Africa’s developing cities. With 68% of the continent’s population expected to be living in cities in 2050, resilient construction needs to “turn towards pragmatic approaches with direct implications on human livability,” said Zaheer Allam, an urban sustainable futures researcher based in the Republic of Mauritius.

Singh agreed. “We see, for example, in South Africa, low-cost houses are quite vulnerable to a small amount of earthquake shaking as compared with well-constructed houses. Funny enough, some traditionally built houses perform better during…earthquake shaking,” she said.

Translating the Model into Action

Paul cautioned that the new model cannot be used to make decisions that are specific to individual buildings or neighborhoods, as it does not represent building-by-building statistics.

Instead, said Mubiwa, African policymakers and practitioners can use the model as a tool for informed decisionmaking in terms of development and building design standards. “This science should find expression in the policies and climate action, mitigation, adaptation, and means of implementation strategies.”

“Our hope is that future researchers and practitioners can use [these] data to model disaster risk and mitigation strategies for a variety of hazards and purposes throughout the continent,” Paul said. “We’ve made the model open and key assumptions within the model transparent so that others can provide feedback and improve the model as additional information becomes apparent or available.”

—Munyaradzi Makoni (@MunyaWaMakoni), Science Writer

Citation: Makoni, M. (2022), New hazard exposure model for Africa, Eos, 103, https://doi.org/10.1029/2022EO220170. Published on 31 March 2022.

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