Date of Graduation

7-2020

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Geosciences (PhD)

Degree Level

Graduate

Department

Geosciences

Advisor/Mentor

Aly, Mohamed H.

Committee Member

Cothren, Jackson D.

Second Committee Member

Dumond, Gregory

Third Committee Member

Tullis, Jason A.

Keywords

East African Rift System (EARS); Fuzzy Logic Modelin; GIS; Geodatabase; Geohazard assessment; Landslides; Risk assessment

Abstract

East Africa encompasses numerous developing countries and involves one of the most active continental rifts on Earth; namely, the East African Rift System. This region is prone to diverse geohazards due to its geographical location at the plate boundary. Several damaging events had happened across the region and more are predicted to occur in the near future. Therefore, it is crucial to investigate, assess, and forecast natural hazards and potential risks in the region. In this dissertation, remote sensing and Geographic Information System (GIS) were employed to conduct three independent studies focused on assessing geohazards in east Africa. Each study is presented in a paper format in a separate chapter in this dissertation as the papers are either published or being considered for publication in peer-reviewed journals.

The first study addressed desegregation of remote sensing and GIS to characterize fluctuations in the surface water area of the Afar lakes in Ethiopia during 1998-2016. Landsat 5, 7, and 8 images were processed using a GIS density slice technique to reclassify the near infrared bands. A time series of surface water area changes for eight lakes was created to examine why these changes have occurred and to determine the main factors that have controlled lake fluctuations over the years.

The second study has been focused on a hazard assessment for the Grand Ethiopian Renaissance Dam (GERD). The dam is constructed in northwest Ethiopia across the Blue Nile and has created a geopolitical dispute between the upstream country (Ethiopia) and the downstream countries (Sudan and Egypt). The downstream countries are concerned about the dam’s safety and its anticipated potential negative impacts on their agricultural activities, environments, and residents. In this study, a weighted GIS model was created to assess hazards at GERD and its surroundings. Nine factors, including earthquakes, volcanoes, faults, fractures, lithology, slope, soil, and precipitation, as well as depth to the groundwater table, were considered and weighted via the Analytical Hierarchy Process. Then, a weighted overlay was established to evaluate local hazards in the study area.

The third study has been dedicated for assessing landslide susceptibility in Kenya. Southwest Kenya is naturally prone to landslides and has experienced recent landslide events that killed people and damaged its infrastructure and environment. About 130 historical landslide events were used to determine the main factors influencing landslide occurrence in Kenya. Factors such as precipitation, lithology, slope, elevation, soil, land-cover, faults, earthquake events, and streams, and roads were determined. Weighted overlay and fuzzy logic models were then created to produce landslide susceptibility indices for Kenya.

The three aforementioned studies have provided crucial details and unprecedented results that are necessary for the decision makers to mitigate the impact of inevitable geohazards in east Africa. This research project suffered from the scarcity of geospatial data and relevant publications over the selected study areas. I hope that my peer-reviewed publications and research outcomes will fill in this gap, will raise awareness in the encountered developing countries, and will support future research with precious datasets.

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