Browsing by Author "Assefa, Alazar"

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    Design With Terrain and Gravels: Nature-Based Drainage Solutions for Sustainable Stormwater Management of Urban Areas
    (2019-11) Assefa, Alazar; Bergen, Marina (Professor)
    Rapid urban growth and global climatic variability result in frequent flooding in urban areas and pose unprecedented stress on the existing drainage infrastructures. In developed nations, a shift in urban stormwater management from relying exclusively on gray, pipe-based drainage infrastructures towards green, nature-based approaches referred to as Sustainable Drainage Systems (SuDS), among others, is currently taking place. In cities of developing countries, the existing gray infrastructures are not well developed, prompting an opportunity of performing a technical leapfrogging towards SuDS. Through vigilant adoption of this increasingly-practiced nature-based drainage solution, municipalities can provide better drainage and flood control and create a fertile ground for more co-benefits to local residents in terms of livelihood and livability. This Ph.D. thesis identifies options to improve the drainage challenge of settlements developed over higher slope terrains and low lying plains of urban areas in developing countries with the high rate of urban growth and drainage infrastructure deficit, through terrain modifications and introduction of gravel-based drainage design solutions as a nature based drainage option to control flooding and provide co-benefits. The study is presented in three parts based on two empirical studies from case sites, both developed in the south-western fringe of Addis Ababa, Ethiopia, and one desktop study building upon one of the empirical studies. The case studies present the design of novel drainage and stormwater harvesting solutions constructed by using locally available materials and terrain modifications. The first design is for drainage of cobblestone streets in hilly areas. The design is referred to as Infiltration Bumper with Tree Planter (IBTP) and targets flood prevention, groundwater recharges and city greening simultaneously. The second design is for the management of stormwater in low lying residential areas. The design is referred to as Elevated Retention and Detention Basin (ERDB), and targets waterlogging prevention, stormwater harvesting, and green area improvements. The first solution (IBTP) is developed and tested to control stormwater runoff generated from the local cobblestone streets within the designated case study catchments for a 2-year storm event corresponding to 40 mm over 2 hours. The second solution (ERDB) is developed and tested to control 100% stormwater runoff generated from the Jemo condominium (the multistory residential neighborhood in Addis Ababa) within the designated case study catchments for the same storm event. The desktop-study resulted in a GIS-based planning tool for upscaling of the IBTP to a city-wide solution.
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    Enhancing Green Infrastructure and the Thermal Quality of Bare walls through Vertical Greenery Technology: The Case of Institutional Plots in Addis Ababa, EiABC campus
    (EiABC, 2018-10) Mohammed, Abdelwehab Yehya; Assefa, Alazar
    Globally, flooding and Urban Heat Island effect (UHI) increase are among the alarming environmental problems of urban centers. Ethiopia, as part of the global temperature increase, is facing the challenge several times. In addition to the global increase in temperature, Addis Ababa, the capital city of Ethiopia experiences the UHI effect phenomena in recent times. The rapid construction of buildings and lack of sufficient Green Infrastructures in the city are contributing to UHI formation. Specifically, the existing bare walls on buildings and other gray infrastructure, without local climatic consideration during their design and development process, contribute to UHI effect formation. The research mainly investigated how to enhance the Green Infrastructure of the city and thermal quality of bare walls through innovative and cost-effective vertical green design and technologies. To realize this, the research first tried to identify bare walls of selected buildings which are the main source of UHI effect; secondly to design living block prototypes for living wall construction and finally to develop the scale-up strategy by taking a case area of the public buildings for their UHI effect reduction and stormwater management effectiveness. Both qualitative and quantitative methods were applied in the study by selecting sample buildings within the EiABC compound. In addition, a case area was selected for scale-up strategies. The selected buildings as a case in EiABC campus consist of Urban Building, Library Building, Student Café and Dormitory Building and Workshop with the potential to recompense 49%, 12%, 58% and 45% of their footprint respectively by changing their bare wall into a living wall using the proposed prototype design. The scaling up test is carried out on sample condominium building blocks, which is typical in Addis Ababa, reveals that the design can utilize 16.4% of their annual roof rainwater runoff and can decrease their surface temperature by 11 Degree Celsius by changing their bare walls into the Living Wall. Finally, the study concluded that bare walls of buildings, fences, shear walls and retaining walls are among major structure with huge potential for Green Infrastructure development in order to reduce the impact of flooding and local climatic modification in Addis Ababa and other densely developed cities. Motivating vertical greening practices, setting regulations for bare walls to be green with further researches on the structural stability of living blocks is the major part of the recommendations of the study. Key Words: Stormwater Management,
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    Improving Stormwater Management Capacity of Cobblestone Paved Local Streets Through Green Infrastructure Design and Technologies (The Case of Resedential District In the Eastern And North Eastern Part of Addis Ababa)
    (Addis Ababauniversity, 2016-09) G/wahed, Fikreselam; Assefa, Alazar
    Addis Ababa is currently undergoing city wide transformation with respect to its built environment and provision of basic infrastructure services. Local street construction with cobblestone pavement is one of the infrastructure development implemented in every part of the city. However, the constructed local streets in many parts of the city are deteriorating within a short time after construction. Therefore, the main objective of the study is; to device green infrastructure design and technologies for the local streets of Addis Ababa in order to reduce the impact of stormwater runoff and at the same time to enhance environmental quality of the city neighborhood. In order to accomplish the objective, research methods were developed for each specific objective. Case study method is then used in the research, by selecting two areas in Addis Ababa that are found in the same local watershed, based on appropriate criteria. Consequently, the existing situation of local streets and impact of stormwater runoff in the study areas is analyzed. Based on the research findings, the research proposes site specific green street design and technologies for the local streets of the study area. Moreover, the research tested and illustrated the upscale effect of green infrastructure practices on watershed level using Arc GIS platform. Key words: Cobblestone pavement, local watershed, green Street, upscale effect
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    Water sensitive urban design for environmnetal quality Improvement of rivers in addis ababa: the case of finicha River
    (Addis Ababauniversity, 2015-06) Tesfaye, Mahlet; Assefa, Alazar
    Nearly all urban areas developed on riverbanks. For centuries, people have settled along rivers for the purpose of irrigation, transportation, water supply, etc. Rivers are also important source of food for people settled close to their banks. Intensive usages of rivers by human beings for the aforementioned purposes have resulted in the loss of aquatic fauna and flora. This is true for Ethiopia as well. Specially, in Addis Ababa, rivers and riversides are neglected places where solid and liquid wastes are dumped. Additionally, it is also a place for legal and illegal settlers. For this reason, the riparian areas along the city’s rivers were shrinking in size, and there are no greenways along the city’s Rivers. Therefore, the main objective of this study is to develop design strategies by testing on a specific site. In order to achieve the objective, cross-sectional study method is selected. This method is chosen because it examines one specific site, while several outcomes are expected at the same time. In addition, study area was selected based on location, land use, exposure to flood and river pollution using purposive sampling techniques. During the study, it is found that the factors for shrinking of the riparian zones of case area are population growth; settlements along the riverbanks; waste dumping site; lack of awareness and coordination as well as inadequate manpower. Furthermore, the factors that increase flood damage and river pollution of the study area are absence of Stormwater Management Practices (SMPs); due to lack of coordination among different concerned Institutions such as AAEPA, MUDC, CBGB,OAAOSZIDP as well as disposal of solid and liquid wastes around the river. There are no greenways along the river. For these reasons, Finicha River is not suitable for the community of the study area. Therefore, the concerned bodies should take appropriate action as soon as possible. There should be coordination among the concerned sectors. In addition, SMPs should be incorporated into built environments such as buildings, road, parking areas and open spaces. Site-specific design solutions should be provided with a view to having urban river spaces that are accessible, attractive and environmentally sound
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    Water Sensitive Urban Design intervention for the alleviation of water scarcity in the government schools of Yeka sub-city
    (Addis Ababauniversity, 2016-10) Assefaw, Kagnew; Assefa, Alazar
    The provision of improved water supply in primary schools is vital service for the well-being of students in urban areas of the country. In order to ensure water supply of schools in Addis Ababa, we need to consider the proper use of the resources and other sustainable source of water. The main objective of this paper is to scrutinize the scarcity of water in schools of the city and alleviate shortage by improved water supply. In order to achieve this objective, the combinations of qualitative and quantitative research approach were employed. The research method applied in this research is applied research by observation the challenge in water shortage in Kara-Alo primary school. Furthermore, identification of key challenges and potential of case sites to come up with appropriate design solution and compare the result of design interventions with the pre-development situation. The key finding of the research identifies. The main factors that cause the water scarcity in the schools as well as in the sub city were; water demand for the growing population, rainfall fluctuation, poor water management practices, poor water infrastructure, climate change and economic challenges. Therefore, the study recommends the possible solutions to minimize the problem of water scarcity by reducing flooding, at the same time application of water harvesting design for the rooftops and ground surface within the school compound are proposed as the primary strategy of the research. The secondary strategy is to educate people so as to not waste water, to identify more water sources and also to protect the flow of water over the ground surface without use. Keywords: Rainwater harvesting, water scarcity, and institutional development