Environmental Impact Analysis of Infrastructures Development and Lake Beseka Expansion on the Integrity of Fentale-Metehara Blister Caves in the Main Ethiopian Rift
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Date
2017-01
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Addis Ababa Universty
Abstract
This study deals with the analysis of environmental impact of the Lake Beseka expansion and the infrastructures development on the Fentale-Metehara blisters and blister caves in the Main Ethiopian Rift. The Fentale-Metehara blisters and blister caves are unique and spectacular geological features found in such number and extent in this area only. The aerial extent of the blistered region is about 54 km². However, the area of the individual blisters and blister caves ranges from about 7m² to 24000m². Decadal landuse and land cover (LU/LC) change of the area analyzed using supervised classification system of Landsat images have been processed in ERDAS IMAGINE 2014 version. In addition, 161 blister caves and 478 blisters were mapped and documented in a geo-database schema using Google Earth accompanied by detailed field investigation. Susceptibility to destruction of these features has been analyzed based on the frequency ratio technique and non-hierarchical cluster analysis of natural (topographical factors, drainage systems, Lake Beseka expansion and lava flows) and human induced (urbanization, irrigation activities and infrastructure lines) triggering factors. For the susceptibility mapping of these blister fields 119 blisters and blister caves were selected and categorized as affected/threatened blister fields. Most of the blister fields fall on the high to very high susceptibility zones. These techniques revealed that the Lake, irrigation fields and the rapid expansion of the urban settlements led to a destruction of some of the blister fields during the past four decades. It was found out that further expansion of Lake Beseka, as well as the human induced factors including the infrastructure development could lead to further destruction of the remaining blister fields. The LULC analysis further corroborates this conclusion as it has been observed that the Lake Beseka, farmlands and settlements expanded at about 46.2 km², 46.6 km² and 3.3 km² area during the last four decades. In conclusion, proper and well-organized documentation of the blister fields in a geo-database schema and also the high quality susceptibility zonation map, which were produced in this study will help in the preservation efforts of these unique geoheritage resources
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Lake Beseka Expansion