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10. Landslides in a changing tropical environment: the North Tanganyika–Kivu rift region, Africa

Author

Dewitte, Olivier, primary, Depicker, Arthur, additional, Maki Mateso, Jean-Claude, additional, Bielders, Charles, additional, Deijns, Axel, additional, Dewaele, Stijn, additional, Govers, Gerard, additional, Jacobs, Liesbet, additional, Kanyiginya, Violet, additional, Kervyn, François, additional, Kervyn, Matthieu, additional, Kubwimana, Désiré, additional, Mugaruka Bibentyo, Toussaint, additional, Nzolang, Charles, additional, Sibomana, Pascal, additional, Twongyirwe, Ronald, additional, Vanmaercke, Matthias, additional, and Dille, Antoine, additional

Published
2022
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14. Quantifying the impacts of urban gullying at the scale of the Democratic Republic of Congo

Author

Ilombe Mawe, Guy, Lutete Landu, Eric, Makanzu Imwangna, Fils, Nzolang, Charles, Wazi Nandefo, Robert, Poesen, Jan, Bielders, Charles, Dewitte, Olivier, Vanmaercke, Matthias, EGU General Assembly 2021, and UCL - SST/ELI/ELIE - Environmental Sciences

Subjects
Geography, Scale (ratio), business.industry, Urban gullies, media_common.quotation_subject, Environmental resource management, Soil erosion, Soil protection, business, Democratic Republic of Congo, Democracy, media_common
Abstract

Urban gullies cause major infrastructural damages and often claim casualties in many tropical cities of the Global South. Nonetheless, our understanding of this hazard currently remains limited to some case studies, while the impacts at larger scales remain poorly quantified. Here, we aim to bridge this gap by making a first assessment of the number of persons and buildings affected by urban gullies at the scale of the Democratic Republic of Congo (DRC). We used Google Earth imagery in combination with local news sources and earlier research to identify 25 cities in DRC where urban gullies occur at a significant scale (at least ten urban gullies). This list is likely exhaustive. Next, for each of these cities, we used Google Earth and other high resolution images to map all visible urban gullies, evaluate their expansion rate and inventorize detectable damages to houses and roads. In total, more than two thousand urban gullies were mapped across the 25 affected cities. Overall, the problem of urban gullies in DRC is especially acute in the cities of Kinshasa, Mbujimayi, Tshikapa, Kananga, Kabinda, and Kikwit. Over 80% of these gullies were active during the observation period (typically from 2002 to 2020). We identified 4257 houses and 998 roads that were destroyed because of the formation and expansion of urban gullies. Nonetheless, the actual impacts are likely much larger since the limited amount of imagery available does not allow quantifying all impacts. For example, in most cases, a large urban gully was already present on the earliest image available.We also made an estimate of the total number of persons that are directly affected, as well as the number of persons currently at risk. Using high resolution estimates of population density and taking into account the current position of urban gullies, we estimate that a total of 133000 people have already lost their house due to formation and expansion of urban gullies. Given that these gullies are typically less than 30-years old, we estimate that on average, at least 4000 people/year lose their house as a result of urban gullies in DRC. This may still be an underestimation. By considering the population that lives in the direct vicinity (Overall, this research shows that urban gullying is a very serious problem in the DRC, but likely also in many other tropical countries. More research is needed to better understand this processes and, ultimately, to prevent and mitigate its impacts. The results and the database of this study provide an important step towards this.

Published
2021

15. Quantifying the impacts of urban gullying at the scale of the Democratic Republic of Congo

Author

UCL - SST/ELI/ELIE - Environmental Sciences, Ilombe Mawe, Guy, Lutete Landu, Eric, Makanzu Imwangna, Fils, Nzolang, Charles, Wazi Nandefo, Robert, Poesen, Jan, Bielders, Charles, Dewitte, Olivier, Vanmaercke, Matthias, EGU General Assembly 2021, UCL - SST/ELI/ELIE - Environmental Sciences, Ilombe Mawe, Guy, Lutete Landu, Eric, Makanzu Imwangna, Fils, Nzolang, Charles, Wazi Nandefo, Robert, Poesen, Jan, Bielders, Charles, Dewitte, Olivier, Vanmaercke, Matthias, and EGU General Assembly 2021

Abstract

Urban gullies cause major infrastructural damages and often claim casualties in many tropical cities of the Global South. Nonetheless, our understanding of this hazard currently remains limited to some case studies, while the impacts at larger scales remain poorly quantified. Here, we aim to bridge this gap by making a first assessment of the number of persons and buildings affected by urban gullies at the scale of the Democratic Republic of Congo (DRC). We used Google Earth imagery in combination with local news sources and earlier research to identify 25 cities in DRC where urban gullies occur at a significant scale (at least ten urban gullies). This list is likely exhaustive. Next, for each of these cities, we used Google Earth and other high resolution images to map all visible urban gullies, evaluate their expansion rate and inventorize detectable damages to houses and roads. In total, more than two thousand urban gullies were mapped across the 25 affected cities. Overall, the problem of urban gullies in DRC is especially acute in the cities of Kinshasa, Mbujimayi, Tshikapa, Kananga, Kabinda, and Kikwit. Over 80% of these gullies were active during the observation period (typically from 2002 to 2020). We identified 4257 houses and 998 roads that were destroyed because of the formation and expansion of urban gullies. Nonetheless, the actual impacts are likely much larger since the limited amount of imagery available does not allow quantifying all impacts. For example, in most cases, a large urban gully was already present on the earliest image available. We also made an estimate of the total number of persons that are directly affected, as well as the number of persons currently at risk. Using high resolution estimates of population density and taking into account the current position of urban gullies, we estimate that a total of 133000 people have already lost their house due to formation and expansion of urban gullies. Given that these gullies are typically le

Published
2021

24. Petrogenesis of peraluminous magmas from the Akum-Bamenda Massif, Pan-African Fold Belt, Cameroon.

Author

Nzenti, Jean Paul, Abaga, Barbara, Suh, CheoEmmanuel, and Nzolang, Charles

Subjects
PETROGENESIS, MAGMAS, OROGENIC belts, SHEAR zones, GRANITE
Abstract

Peraluminous intrusives of the Akum-Bamenda Massif, Pan-African Belt, Central Cameroon, were synkinematically emplaced in a Pan-African sinistral strike-slip shear zone. The rock sequences consist of medium-grained leucogranites, fine-grained leucogranites, and orthogneisses of biotite granite composition; in aggregate, they cover a range from about 65 to 74 wt.% SiO2, defining a continuous chemical evolutionary trend and displaying characteristics of the high-K and medium calc-alkaline series. Leucogranites are strongly peraluminous (A/CNK > 1.1) and plot in the field of S-type granites, whereas orthogneisses are metaluminous and plot in the field of I-type granitoids. Major and trace element compositions and the Rb/Sr isotopes of the leucogranites indicate crustal derivation by remelting of a composite metapelite + metagreywacke protolith similar to the metasedimentary rocks of the central domain of the Cameroon Pan-African North-Equatorial fold belt. [ABSTRACT FROM AUTHOR]

Published
2011
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