Explanatory Notes
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GEOLOGICAL HAZARDS AND ENGINEERING GEOLOGY MAPS OF DILA NB 37-6 EXPLANATORY NOTES Habtamu Eshetu (Chief Compiler) Vladislav Rapprich (Editor) The Main Project Partners The Czech Development Agency (CzDA) cooperates with the Ministry of Foreign Affairs on the establishment of an institutional framework of Czech development cooperation and actively participates in the creation and financing of development cooperation programs between the Czech Republic and partner countries. www.czda.cz The Geological Survey of Ethiopia (GSE) is accountable to the Ministry of Mines and Energy, collects and assesses geology, geological engineering and hydrogeology data for publication. The project beneficiary. www.gse.gov.et The Czech Geological Survey collects data and information on geology and processes it for political, economical and environmental management. The main contractor. www.geology.cz AQUATEST a.s. is a Czech consulting and engineering company in water management and environmental protection. The main aquatest subcontractor. www.aquatest.cz Copyright © 2014 Czech Geological Survey, Klarov 3, 118 21 Prague 1, Czech Republic First edition AcknowledgmentAcknowledgment Fieldwork and primary compilation of the map and explanatory notes was done by a team from the Geological Survey of Ethiopia (GSE) consisting of staff from the Geo Hazard Investigation Directorate, Groundwater Resources Assessment Directorate and Czech experts from AQUATEST a.s. and the Czech Geological Survey in the framework of the Czech Development Cooperation Program. We would like to thank the SNNPR Regional Water Bureau, the Dila, Sidamo and Sodo- Woleita Zone Administrations, Water, Mines and Energy offices for their hospitality, guidance and relevant data delivery. The team is grateful to the management of the Geological Survey of Ethiopia, particularly to Director General (GSE) Mr. Masresha G/Selassie and Mr. Lata Alemayehu, Head of the Geo Hazard Investigation Directorate as well as Mr. Muhuddin Abdela, Head of the Groundwater Resources Assessment Directorate for their support. Finally, we would like to acknowledge the untiring support of the local people who assisted the team by all means possible and facilitated the data collection and those who helped us in various different ways. Contents Acknowledgment .........................................................................................................................................................................3 Extended Summary................................................................................................................................................................... 13 Introduction ................................................................................................................................................................................ 15 1. Basic Characteristics of the Area ..................................................................................................................................17 1.1 Location and Accessibility .......................................................................................................................................................17 1.2 Population, Settlements and Health Status ........................................................................................................................18 1.3 Land Use and Land Cover .......................................................................................................................................................22 2. Selected Physical and Geographical Settings ........................................................................................................... 25 2.1 Geomorphology .........................................................................................................................................................................25 2.2 Soil and Vegetation Cover .......................................................................................................................................................28 2.3 Climatic Characteristics ...........................................................................................................................................................29 2.3.1 Climatic Zones and Measurements...................................................................................................................................29 2.3.2 Wind speed and direction ...................................................................................................................................................32 2.3.3 Precipitation ............................................................................................................................................................................33 2.4 Hydrology of the Area ..............................................................................................................................................................38 2.4.1 Surface Water Network Development .............................................................................................................................38 2.4.2 River Flow Regime ................................................................................................................................................................39 2.4.3 Lakes .........................................................................................................................................................................................48 3. Geological Settings ...........................................................................................................................................................51 3.1 Previous studies .........................................................................................................................................................................51 3.2 Stratigraphy ................................................................................................................................................................................51 3.3 Lithology ......................................................................................................................................................................................52 3.4 Tectonics .....................................................................................................................................................................................59 3.4.1 Primary structures .................................................................................................................................................................59 3.4.2 Ductile structures ..................................................................................................................................................................59 3.4.3 Brittle structures ....................................................................................................................................................................63 3.5 Geochronology ..........................................................................................................................................................................66 3.6 Geological Evolution .................................................................................................................................................................67 4. Rock properties and economic perspectives ............................................................................................................. 69 4.1 Engineering geology .................................................................................................................................................................69 4.1.1 Engineering classification of rocks .....................................................................................................................................69 4.1.2 Engineering classification of soils ......................................................................................................................................75 4.2 Economic geology ....................................................................................................................................................................78 4.2.1 Construction materials .........................................................................................................................................................78 4.2.2 Absorption materials ............................................................................................................................................................82 4.2.3 Ceramics materials ................................................................................................................................................................83 4.3 Geothermal energy ...................................................................................................................................................................83 4.4 Geotourism potential ................................................................................................................................................................84 5. Geological hazards ........................................................................................................................................................... 85 5.1 Endogenous geological hazards ............................................................................................................................................85