Urban Design

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Low Impact Development (LID) Design Retrofit to Reduce the Impact of Flooding and Diffused Pollutants from Affecting the Urban Lakes, The Case of Hawassa City, Ethiopia
(Addis Ababa University, 2022-06-01) Yared Dereje; Alazar Assefa(PhD)
Rapid urbanization has become a prevalent trend in the twenty-first century, putting development pressures on existing urban areas as a result of socio-economic changes, which has an impact on the natural system, particularly the hydrological system, by increasing flooding and degrading water quality. The recent expansion and densification of Hawassa city contribute greatly to the generation of more pollutants, which are transported to the city's lake through stormwater runoff from built-up areas. The objectives of the study is to see how fast urbanization impacts the city's natural environment, particularly the lake ecology, while also addressing sustainable stormwater management to safeguard the city's lake using the Low Impact Development (LID) site design approaches. The city's natural and man-made land cover were investigated to determine the source of Lake Hawassa's ecological problem, which was connected to an increase in impermeable surfaces. In this regard, the study used a data set that included a Digital Elevation Model (DEM), a high-resolution satellite image, an existing land use map, precipitation data, and water quality samples. Using spatial analysis tools in QGIS 3.6.3 and a simulation model in SWMM 5.1, the quantity and quality of stormwater runoff impacting the lake environment were evaluated. The imperviousness level of 14 sub-catchments that directly flow into the lake, as well as the pollution load from impacted catchments, have all been investigated to determine which sub-watersheds contribute the most pollutants to the lake. The study revealed that between 2013 and 2018, the imperviousness level in catchments that directly drain to the lake increased from 12.20 % to 20.32 %. That shows an increment of 43.4 % of runoff from impervious covers within five years period. COD, TSS, TN, and TP levels in water samples tested from the degraded catchments' lake intake streams were 2307.5, 510.5, 2.09, and 10.4 mg/l, respectively, which are all above the permitted range. The SWMM model's simulation results also show that surface water quality is substantially degraded and exceeds acceptable limits. The study identified various types of LID design features as well as potential retrofitting open spaces in the study catchments. After incorporating the proposed LID retrofits, simulated results reveal a reduction of 16.0 % and 17.4 % in stormwater runoff and peak flows for catchment 10 (C10) and a drop of 66.3 % and 5.0 % for catchment 11 (C11). Regarding to water quality, the COD, TSS, TN, and TP pollutant loads were reduced by 16.5 %, 16.2 %, 16.3 % and 16.3 %, and for C10 and 26.7 %, 13.1 %, 26.6 percent, and 26.2 %, for C11 respectively. Finally, flooding and water quality impairment shows the disruptions in the urban hydrologic cycle resulting from the construction of more impermeable surfaces have contributed to the degradation of Hawassa Lake's water quality. Incorporating effective LID solutions into the city watershed management systems and limiting a significant increase in impervious surfaces in urbanized catchments has the potential to reduce urban flooding, nonpoint source pollution into the lake, and the oncoming environmental crisis.
Mapping the Level of Active Frontage in Addis Ababa city, Ethiopia
(Addis Ababa University, 2022-11-01) Ametu Mohammed Oumer; Tibebu Assefa (PhD)
Active frontages have high value for city development. However in Addis Ababa fence properties, blind walls and streets which make its frontage inactive and repressive for citizen, passersby and visitors. Blind walls or street frontages with few openings are deterring. The study aims to measure active frontage level of Addis Ababa city. Active frontage level in Addis Ababa city was identified on field observation and by applying Arc GIS software digitize and give attribute of each frontage level data obtained from field survey,(captured photos in walk-along), analyze, interpret, map out active frontage level map and rated active frontage level. Accordingly the city has been rated frontage level from A to E. Where frontage level A is full of widows and inviting and frontage level E is for passive frontage. The study investigated that the level of active frontage level in Addis Ababa city was depends on street type, building function, fence and building structure. The result showed that 85.6% of AA is passive while 14.4% % is active. The study found that from the total active street segments in Addis Ababa city 55.6% is both side active streets and 44.4% is one side active streets either right or left side. This shows that even the active streets in Addis Ababa city are not fully active. So the responsible body needs to take action by identifying potential active area by issuing relevant regulation and redistributing magnet buildings
Space- Syntax as a Tool for Place Making by Restructuring Public Spaces Within Mixed-Residential Areas Of Addis Ababa, the Case Of Meskel Flower District
(Addis Ababa University, 2022-04-01) Daniel Sileshi Leggese; Alazar Assefa (PhD)
Placemaking is a process that inspires people to reinvent or reimagine public spaces as the heart of every community. It also strength the connection between peoples and places they share. The main existing problem in the study area is the existence of fewer open spaces when compared to standards. The existing open spaces are not providing the intended services and most of them are leftover spaces without any function and some are even used for emerging slum housing. The general objective of this study is identifying spatial capital of the neighbourhoods and redesign open. In this paper analytical research is used together with qualitative and quantitative data types. Software like GIS, AUTOCAD, and depthmapX are used for data analysis. The main finding from this paper is, the Study area is poorly connected in relation to the required function, the linkage and integration of public spaces with people's primary uses are poor and roads within residential areas have poor connection and are characterized by dead ends. So, the overlayed street integration and open space map was developed in response to creating functional open spaces to achieve the desired mixing of functions and accessibility based on the standards, which provides responses to the problems that were collected and analysed. This study attempts to provide sample design proposals of selected areas or nodes of the overlayed map, with placemaking as the main focus area.
The Chair of Conservation of Urban and Architectural Heritage Presented in Partial Fulfillment of the Requirements for the Degree of Master of Science
(Addis Ababa University, 2022-05-01) Eden Fikramariam; Tadesse Girmay
Conservation of urban heritage is a ‘value’ based approach and scholars in the fields of conservation and developers have been aware of such values including the socio-cultural as well as economic values. The objective of this paper is to study the urban heritage located in the center of Addis Ababa, specifically in Leghare area that has become the subject of intervention due to the values of the place. It specifically aims at the change, propose a tool for assessing and mitigating these changes and achieve a common ground where the development of the city won’t affect the existence of urban heritage and where the conservation of such places contributes to the growth of the city. The general methodology used for this research is a case study method focusing on pattern matching and triangulation techniques. It employes the assessment of change by analyzing the Heritage value and relies on the interrelation between intervention approaches of the socio-cultural and economic values of heritage places using primary and secondary data sources. The primary data is collected by direct observation and interviewing and the secondary data is extracted from different published documents, archival records, photographs, written reports on events and formal studies. Based on the data gathered and analysed this paper finds that the urban heritage of Leghare is faced with destructive intervention and is subjected to deterioration in need of immediate conservation and integration measures. Based on the findings, the paper concludes that, there is a strong mutualism between the socio cultural values of urban heritage and the development of urban places in the city. Therefore, it is recommended to provide a participatory approach between conserving the core urban heritage values for the sustainable socio-cultural and economic development of the city.
Factor Affecting the Public Transportation Modal Chioce in Urban Moblity in Addis Ababa: The Case of Yeka Sub City.
(Addis ababa University, 2022-04) Abebe, Fentahun; Girma, Birhanu (Phd)
The modal choice in Ethiopia varies from passenger to passenger due to different factors. The existence of modal choice creates different problems like delays, traffic accidents and traffic congestions etc. The general objective of this research was to analyze the factors that affect the modal choice in urban mobility in Addis Ababa; the case of the Yeka Sub-city. To achieve the above objective, the researcher used simple random sampling technique to select samples for both open and close ended questionnaire method, and purposive sampling for the semi structured interview method. The sample size of this study was 378 samples, from these samples 40 of them were interviewed, the remaining 338 respondents filled the questionnaires. This research is a mixed type of research, meaning that by using both quantitative and qualitative data describes the factors that affect the modal choice in urban mobility in Addis Ababa; in the case of the Yeka Sub-city. The research design of this research was concurrent research design means the collection of qualitative and quantitative data simultaneously, specifically Quantitative driven concurrent design (QUANT + quall) where used for this study. The study found out that Personal Information (gender, employment status, family size, and income status,), Characteristics of Trip (travel purpose, travel time, travel distance, and Transport cost), Psychological factors (attitudes towards buses, and attitudes towards buses) and characteristics of the transport facility (comfort, safety, and availability of vehicle) are statistically significant. In addition there are factors which are related with spatial data like availability of parks, urban land use type and design and network of roads which affects the modal choice .From the findings, 75.4%) of the participants used taxis (all taxies which carries 11_12 passengers), 24.6% of the participants used buses (both Sheger and Anbesa buses).So taxis were the most common mode of transport used in Addis Ababa especially in Yeka Sub city. The choice of transport modes affects the urban mobility because it is the means of traffic congestion ,dalliance ,accidents and other environmental problems related with mobility, especially the choice of taxis that aggravate those problems above than buses. To minimize this problem the government and concerned stakeholders should manage the transport system like Higer, Shger, and also and Anbessa bus in their safety and comfort to make it competitive to other transport modes; Supply adequate transportation modes especially supply buses which can enhance the transport service.
Nature Based Orainage Solution for Minmizing the Risk of Flooding in Nekemte City
(Addis Ababa University, 2020-12) Feyisa, Nuywalif; Assefa, Alazar (PhD)
In Ethiopia, the recent urban expansion and increment of impervious surfaces in high rainfall areas resulted in flooding and associated environmental problems. Nekemte city is one of the urban centers in the country facing the challenges associated with a high level of imperviousness and flooding. This study mainly focused on estimating the level of impervious surfaces and introducing nature-based drainage design solutions for sustainable stormwater management of the city by targeting water-resilient strategies for the future of Nekemte. Spatial data collected and processed by using ArcGIS for mapping & quantification of impervious surfaces eventually for calculating stormwater runoff generated from the most impacted watershed. None spatial data collected to understand the perception of local people about the situation of flooding using questionnaires, structured interviews, observation & focus group discussions. Published and unpublished documents from the municipality of Nekemte and planning institutes utilized for verification of both spatial and non-spatial data. The collected primary data analyzed statistically under SPSS version 20. The principal result of this research showed that factors enabling flooding problems are the sum of factors associated with impervious surface increments, intensive recurrent rainfall in the area, densification of settlements in the higher slopes, and inadequate drainage facilities for stormwater management. Based on this factor, the watershed that covers the area around Bake Jama and nearby neighborhoods estimated to be 201.06ha watershed area identified as the most impacted with 95.77ha of impervious surface coverage. The problem associated with imperviousness in this particular watershed can be reduced by retrofitting through the application of nature-based drainage solutions using the available open spaces and public realms. The study also developed watershed level strategies applicable in different parts of the city with similar flooding problems. Finally, the study recommended further assessment of the socio-economic aspect of flooding in the area to link the nature-based drainage solutions with more co-benefits for the local people affected by flooding. In this regard, the designed nature-based solutions as a blue green system have the potential for creating more jobs and income for the local people through water harvesting and urban farming schemes
Identifying Potential Wind Energy Harvesting Sites for Sustainable Development of Debere Berhan Town, Ethiopia
(A.A.U, 2021-06) Workneh, Aboma; Assefa, Tibebu(PHD)
In the modern world, renewable energy resources are a very important segment and critical input for the development of human life which provides energy for electricity. Renewable energy resources are naturally refilled by nature with short time such as wind, sunlight, and others, and have less impact on the environment. Site selection is an important step for the utilization of those renewable resources. The method of primary and secondary data analysis by using multi-criteria decision-making (MCDM) was used for site selection using ArcGIS as a tool. The potential sites for wind energy harvesting take into account four major groups (topographic, technical, environmental, and socio-economic aspects of wind farm development) and eight sub-criteria groups (slope, wind speed, distance from existing power lines, rivers, LULC, distance from urban areas, distance from roads, and wetland). All the layers and datasets are weighted and overlayed to determine weights of sitting criteria to select the best and feasible site according to their importance for the wind farm site selection. The most suitable areas both inside and around Debere Berhan town have been presented on the wind farm suitability map and windy map of Debere Berhan town. From the total study area around Debere Berhan town, 31.4 % is most suitable for wind energy harvesting which covers about 2,507.2 ha of land, and from this area, approximately the estimated energy is about 60.18 MW. Locations for urban wind energy also identified inside Debere Berhan town which covers about 189.2 ha of land in four different places and these areas can be used as building-integrated wind turbine (BIWT) for energy harvesting within the town and about 3.82 MW of energy is estimated from urban wind energy resource within Debere Berhan town. Finally, the urban design plan for the wind farm of Debere Berhan town is developed and mapped.
Investigating the Optimum Building Density and Lake Tana’s Breeze in the Case of Bahir Dar City, Ethiopia
(2021-05) Ngrie, Zelalem; Assefa, Tibebu(PHD)
The ideal built-up density for proper ventilation of Bahir Dar city is proposed using a method of performing city-scale ventilation assessment based on remote sensing, GIS, and CFD technology. The ventilation of a city depends on the location and background ventilation source. Bahir Dar is a city found south side of Lake Tana and beginning of River Abay. The ventilation background is assessed using meteorological data of wind direction and speed. The numerical simulation of ventilation potential index performance have done using roughness length (RL), sky view factor (SVF) and computational fluid dynamics (CFD). In this study, the roughness length (RL) determined the land use land cover of land sat 8 and the building morphology of existing development. The sky view factor (SVF) is estimated and calculated by using 30m high resolution digital elevation model by SAGA GIS. The general wind pattern and ventilation of the existing high rise building is evaluated by CFD simulation. Generally, the existing ventilation performance of Bahir Dar is relatively high. But in the southern part of the city ventilation is moderate (general) and low. The new structure plan of Bahir Dar city have been checked by the above criteria and the result shows high roughness length and low ventilation performance because of high density development proposal and block Lake Tana breez’s. Suitability map developed by using multiple criteria; exiting ventilation potential, major ventilation source, urban ventilation corridor buffering standard and sky view factor have been used to produce suitability map of urban ventilation corridor design. The ventilation corridor design result perform a ventilation potential index value 0.4 with low roughness value of 0.5 and high sky view factor 0.67. Accordingly, the municipality of Bahir Dar should adopt an optimal citywide development density of not more than 50%, a minimum of 15m distance between buildings, and a maximum building size (footprint) of 20m x30m.
Nature-based Design for Stream Rehabilitation Affected by Imperviousness in Addis Ababa: The Case of Kaba River
(Addis Ababa University, 2020-10) Abebe, Mengistu; Assefa, Alazar (PhD)
Urbanization of watersheds substantially changes the health of a stream by increasing impervious surfaces that deliver pollutants directly to waterways. The major environmental problem that Addis Ababa facing is the increasing impervious surface. Although improving the riparian zone has been attempted to restore urban stream health in Addis Ababa, that does not significantly improve it, since it is not equivalent to the scale of degradation of streams based on recent studies. The main objective of the study is to introduce an appropriate type of watershed-level nature-based design measures for the rehabilitation of urban streams affected by the higher level of imperviousness in Addis Ababa. Stream restoration can be achieved in this case by a cross-sectional study of the specific case watershed to address the issue of urban streams and river system rehabilitation at the watershed level by introducing appropriate nature-based design solutions and by upscaling the solution from the case site into the entire city river system. The study site is selected based on the density by comparing the built-up of upper catchments. The study estimates the existing level of effective impervious area for ‘Kaba’ river watershed and stream health improvement solution. The total impervious cover of the city and effective impervious cover of the study area are 52 and 27.8 percent respectively. The current condition of the stream will not support its intended hydro-ecological functions. Different design scenarios are proposed in the watershed to reduce the effective impervious areas to a level at which measurable improvement in the ecological indicators. Finally, the study concludes that the proportion of the effective impervious areas is a good predictor of the ecological condition of streams and it should be reduced to a level of recommended proportion to maintain stream health.
Application of Curb Extension for Sustainable Storm Water Management of Local Streets in Water Logging Lands:The Case of Residential Areas in Addis Ababa:
(Addis Ababa University, 2021-02) Beyene, Tsega; Assefa, Alazar (PhD)
The application of sustainable stormwater management system in waterlogging areas of urbanized catchments is the most effective method that helps to control surface stormwater runoff caused by recurrent and extreme rain events. Applying a bio-retention system for flood reduction through infiltration and evapotranspiration processes will help to create an attractive urban street with better environmental performance. Since cities are becoming more impervious, the stormwater runoff increases and will affects the downstream land and water bodies by flooding. In Addis Ababa, applying a sustainable stormwater management system is a timely act due to the ongoing rapid urbanization and increment in impervious surfaces that result in stormwater runoff that causes flooding and surface water pollution. In this regard, innovative and flat terrain considerate design responses are needed in low-lying plains with difficulties to apply conventional pipe-based drainage systems. The design intervention will reduce the waterlogging effect occur due to extreme rain events. The objective of the research is to apply curb-extensions as a bio-retention system for sustainable stormwater management of waterlogging local streets in the low-lying residential areas of Addis Ababa. Specifically, the study identified areas affected by peak stormwater flow that creates a waterlogging problem over local streets of the case study area. A sustainable design solution is proposed by considering the infiltration, retention, and evapotranspiration capacity of curb-extensions. The study identified flooding and waterlogging areas in the city, at the river catchment, and in the study, site using hydrological and spatial data. Using ArcGIS-based hydrologic analyst tools, blue spots located along the flow direction of the streams identified as depressions usually experienced an overflow of stormwater and waterlogging. To minimize the risk of waterlogging, a sustainable design solution as a curb extension system designed by estimating the water balance from the actual water holding capacity of natural depression (blue-spot) and the stormwater runoff generated from the catchment area that naturally drained into the specific blue-spot. The curb-extension system was designed as a bio-retention and streetscape element by modifying the native soil, gravel fill, water intake plants on the top of the system for infiltration and retention purpose. In this regard, the designed curb extension will substantially manage the highest intensity of precipitation (40 mm/hr) of 10 years of rain event from IDF curve of Addis Ababa. The design reduces the volume of stormwater runoff from 22.895 m3 to 8.477 m3, which is 62 % of runoff. The study concludes that if the municipality of Addis Ababa develops a curb extension system over the local streets of the entire neighborhoods affected by waterlogging, the flooding problem will be reduced substantially with more greening & environmental benefits. The system will also contribute to the reduction of downstream flooding by minimizing stormwater runoff flowing into the Akaki river system. As a multifunctional drainage design facility, the system has the potential to create a green street that helps to improve the standard of living and boost the environmental quality of the area. Finally, the study recommended further study on the upscaling of proposed curb-extension by developing more empirical and experimental settings as a pilot project. The pilot projects will help the city to consider the curb-extension system for the greening, drainage design, and urban planning practices. Moreover, the tests and demonstration works will justify its competency for improving the livability and livelihood of the local people within urban settings that were frequently affected by waterlogging.
Identification of Potential Sites for Harvesting Wind Energy in the Town of Dessie, Ethiopia
(Addis Ababa University, 2020-10) Yenenew, Mulugeta; Assefa, Tibebu (PhD)
To find solutions for the global energy crisis, an analysis of a helical vertical axis wind turbine was conducted with the consideration of renewables and energy efficiency. Dessie town, one of the towns in the Amhara region, which uses different energy resources such as wood, charcoal, kerosene, animal dung, and hydroelectric power for heating, lighting, and transport. As the need for energy is increasing, the scratch for harvesting more energy sources is inevitable for cities and towns to be sustainable. This study was carried out in three steps: to map windy area in the town, the realization of the analytical calculation of a helical wind speed turbine power output which then informed the most wind harvesting potential sites. So, this study particularly aimed to address its use as the electricity supply for residential buildings or any other places with less ideal economic conditions. The easy and highly available mechanism using basic materials is to give individuals to have a viable option on their electricity production. Finally, based on findings, the study recommends wind energy could be a convenient planning strategy to inhabit and to supply affordable energy options for the growing urban population. The study also recommends proper energy regulations concerning alternative wind energy to improve, to achieve sustainability, and for the efficient utilization of wind energy.
Assessment of Intervention and Influence of Urban Redevelopment on Architectural Heritages Located in Arada area
(Addis Ababa University, 2019-11) Shawul, Biniam; Girmay, Tadesse
Conservation of urban and architectural heritage in the Arada area is basic to remember the history of Addis Abeba. Currently, the city is experiencing redevelopment activities. The research was assessing urban redevelopment interventions and influences on architectural heritages, for the case of main Street of Churchill and the surroundings. The significance of the study is to conserve architectural heritages from mass destruction due to urban redevelopment. The research was conducted through site investigation, document analysis, interviews and questionnaire surveys. Both qualitative and quantitative data are collected from different sources. The research is mainly qualitative. The quantitative data collected is used to support the results but not as a major source of data or information to reach a conclusion. The research was done through identifying independent factors that affect architectural heritages such as problem of urban heritage management, professional gap, redevelopment, improper structural intervention and natural factors deeply investigated from site investigation and interviews. The research identifies that architectural heritages are vulnerable due to urban redevelopment and lack of understanding the value of heritage. Due to this, the historic buildings were transforming their existing character into modern buildings; In addition, they are missing its historical values. The research would recommends the policy developers and community should be work together to increase the property value of a Arada area. Generally, the study shows that to conserve the architectural heritage located in Arada area, the stakeholders shall be work on revitalization, adaptive re-use, restoration, and renovation.
Determining Ventilation Orientated Optimum Window Size for Urban centers of Ethiopia
(Addis Ababa university, 2020-11) Deriba, Matias; Tibebu, Assefa (PhD
Natural Ventilation is an effective method for passive cooling, increase indoor air quality and minimize energy consumption of a building. Natural ventilation through window openings is an effective solution to bring air into internal spaces and improve indoor environmental condition. In urban centers, where the density is high and local wind is reduced, the geometry of a building and its opening has a massive role in natural ventilation. The current building codes and regulations of Ethiopia miss detailed guidelines for natural ventilation. On the code and regulation for windows are specified only in relation to the floor area regardless of orientation, height, location and climate. Since the country has different climate zone in different regions, the generalized building code and standard will lead to over or under ventilated rooms in both scenarios creates discomfort. The study attempt to determine ventilation-based window size for urban centers of Ethiopia on different façade orientation to increase the effectiveness of natural ventilation. As wind is the main driving force of natural ventilation, regionalizing of Ethiopia according to wind speed and wind direction (secondary-Inter cardinal direction) is presented in order to study the potential of natural ventilation at different regions in the country. The average wind speed is categorized using the Beaufort’s scale of wind speed. The data addresses the urban centers of Ethiopia and the urban centers are selected by density. Both scenarios (single side ventilation and cross-ventilation) are discussed in each zone. Appropriate opening size is determined, using the window orientation with respect to the wind flow direction and also best and worst window orientation is illustrated for each zone. The study verified that, the effectiveness of natural ventilation is associated with wind zone where the urban centers are located.
Developing Parametric Solar Envelope for Ethiopian Cities
(Addis Ababa University, 2020-10) Abebe, Solomon; Assefa, Tibebu (PhD)
The effects of poorly designed buildings in terms of limited access to sunlight on critical times affect the health of building occupants and become the growing concerns about global warming, Ozone layer, depletion of fossil energy source and soaring oil prices. So, planning in a way to allow for sun access by regulating the form, height, orientation and organization of the built environment is important. This paper deals about the design and applicability of solar envelope to residential houses of Ethiopian cities to get access for solar or shade right. Solar envelope is a building volume limit that will not cast shadows on surrounding buildings at specified times so as to create comfortable indoor climate for humans based on the sun’s movement (time) relative to the location and geometry of a site (space). The concept of solar envelope was first developed as a framework for architecture and urban design at the University of Southern California (USC) over the period 1969 to 1971 by Professor Ralph Knowles. For this end, NCEP stations found all over the country were tapped and their heating and cooling degree days have been computed correlating the respective temperature with the standard base temperature, 18.3 o c. Besides, reference cities were identified after the regionalizing Ethiopia based on their respective degree days. Then, sun path diagram for each region has been prepared and used to identify the critical sun angles, Azimuth and Altitude of the sun, for the specified time ranges. Finally, parametric solar envelopes have been developed for each zone of reference city and this will be a basic for energy efficient envelope building creation.
Identifying Streets from Roads of Addis Ababa Using Space Syntax Analysis Tool
(Addis Ababa University, 2020-10) Mulushewa, Feven; Assefa, Tebebu (PhD)
Space Syntax analysis is a tool for analyzing the road system of the city and broadly used for modeling vehicular and pedestrian movements, to control traffic pollution and on the processes of route selection. The existing road system of Addis Ababa face different urban problems and it’s difficult to have standardized streets so, this study explores how to identify important urban roads that have potential to be converted into the street using space syntax analysis tool based on greater consideration of the needs of people, rather than vehicles since street differs from roads. The study uses Addis Ababa’s current and proposed road network for the production of axial line and analysis integration and mean depth at the sub city level to identify major important roads of Addis Ababa and highly segregated roads, respectively. Integrated streets in a system are assumed to be accessible from all other streets and the value range (0-1) lowest value (0.1 -0.5), mid-value (0.5-0.9), and the highest value (0.9 -1.0). The depth is the smallest number of syntactic steps to reach one space from another so, the deepest street means a highly segregated street. According to this assumption core area of the city which has a highly integrated value (>0.9) covers only 4% of Addis Ababa city, and it laid some parts of Kirkos, Lideta, Arada, and Adiss Ketema sub-cities. Also, 28% covered in integration (0.5-0.9), while the peripheral areas (intermediate and the suburbs) are not integrated. The most segregated area of the city is found around the riversides of the city and it needs urgent intervention. Kirkos sub-city has both highly integrated roads and highly segregated areas.
Green Infrastructure Retro-fitting to Protect Urban Streams from Non-point Source Pollutions
(Addis Ababa University, 2020-11) Tsegaye, Emebet; Assefa, Alazar (PhD)
Uncontrolled urbanization causes serious quality degradation of surface waters through covering natural land by impervious surfaces that greatly increases the volume and velocity of stormwater runoff as well as transportation of pollutants from point and non point sources. Therefore, sustainable water management is essential. This study focuses on non-point source pollutants having an objective of identifying Green Infrastructure retro fitting options to protect the stream water from these pollutants in the localized sub watershed around Egziabherab church in Bole sub city of Addis Ababa. Both primary and secondary data were consumed for this study. The secondary data include contour map and base map collected from Addis Ababa plan commission, rain fall data from National Meteorological Agency and other related literatures. The primary data were the land use/cover, street surfacing and stormwater sample directly collected from selected sites. Software such as GIS, spread sheet, ArchiCAD, AutoCAD, Scketchup and laboratory taste were used for analysis and designing purpose. The result indicates that Total Suspended Solids exceed the limit of the recommended standard. Applying permeable pavers on private plots, 21–33.3% of the stormwater runoff and 68–86% of Total Suspended Solids generated from the entire development can be reduced. Rainwater Harvesting from roofs of institutional plots can reduce 6.4–9% of the total runoff. 100% of Total Suspended Solids can be reduced by vegetated swale, rain garden and riparian buffer. Generally, green infrastructure retro-fitting should be an integral part of urban plan and design at all scale to reduce runoff volume and improve stream water quality.
Developing a Thermal Comfort zone Chart for Different Climatic Zones of Ethiopia.
(Addis Ababa University, 2020-10) Fufa, Daba; Assefa, Tibebu (Assistant professor
Thermal comfort is the state of mind that expresses satisfaction with the prevailing environmental condition. The problem of urban environment located in extremely hot and cold parts of Ethiopia is the thermal discomfort and become less suitable for living. This results in a problem of health and high energy consumption for cooling and heating. This study focuses on developing qualitative and quantitative thermal comfort charts for different climate zones of Ethiopia. The data set of air temperature, wind speed, solar radiation, humidity, and precipitation recorded for 30 consecutive years were used and had been obtained from Global weather data for SWAT and EMA. Based on the environmental variable analysis, Ethiopia is classified into six climate zones namely: - Hot-dry, Warm humid, Warm-dry, Temperate, Cool, and Cold. From the finding, more than 53.6 % of the towns of Ethiopia clustered under temperate climate zones. The qualitative and quantitative bioclimatic chart with main passive design strategies were developed for representative cities. In all climate zones, mechanical cooling and heating are not required if the passive design strategies adopted properly except in the harsh season of the hot dry and cold region. The study used as a preliminary guide for climate responsive design and MCUD can utilize it to ensure sustainability. As this study is regional and microclimate is affected by different local factors, developing a similar bioclimatic chart is mandatory for each town and city of Ethiopia
Identification of Potential Sites for Harvesting Wind Energy in the Town of Dessie, Ethiopia
(2020-10) Yenenew, Mulugeta; Assefa, Tibebu (PhD)
THE SOCIAL AND ECONOMIC IMPACTS OF PUBLIC TRANSPORTATION ON ADJACENT COMMUNITIES: THE CASE OF EAST-WEST ROUTE OF THE ADDIS ABABA LIGHT RAIL TRANSIT
(EiABC, 2019-06) DEYAS, GEBEYEW TADESSE; Professor Mintesnot Woldeamanuel
The Addis Ababa Light Rail Transit system is the first modern mass transit system for Ethiopia as well as for Sub Saharan Africa. Although, the Addis Ababa LRT lines/ stations thought to bring either positive or negative or both social-economic impacts on the adjacent communities, after it has been launched there was/were no research done focusing on the socio-economic impacts the LRT on the adjacent community. Therefore, the purpose of this study was to assess the socio-economic impacts of the light rail transit line/stations on the community. To conduct the research, about six LRT stations along the East-West LRT line from Coca-Cola to Ayat were selected by bypassing 3 LRT stations to embrace the Coca-Cola LRT station which is service dominate area, Megenagna the active commercial area and Ayat the residential dominate area since the study focus on the adjacent residential, commercial and social services. Then, random data collection methods were used to collect the data from the community around each LRT stations. Questionnaire surveys, interview and observations methods were used to collect data. There were 720 respondents for the questionnaires and 20 people for an interview to consolidate the quantitative data. Then, the descriptive statistics and spatial analysis methods were administered for data analysis. Using the above approaches, the social and economic impact of the LRT on community in residential, commercial and social service were analyzed. As the result of this, the social and economic impact of the LRT on adjacent community in residential, commercial and social service were analyzed separately using the social and economic impact indicators of the LRT. The community living in the residential areas uses the LRT the most for their trip purpose than the rest of the other adjacent land uses, while followed by the community in the social service, and the least percentage of the adjacent community were those in social services. The LRT has brought both positive and negative socio-economic impacts on the adjacent communities having varied frequency of responses from family to family as well as from station to station. The positive impacts of the LRT for the adjacent community were the transport cost reduction, travel time reduction, increasing volume of retailers around the LRT stations, increasing the volume of the renters in the communities, means of transportations for the community and etc. In contrast to this, the negative impacts of the LRT were segregation of the adjacent communities around the LRT, reduction of the customers from some business activities, long walking distance to access the opposite side of the LRT, inconvenience of the stations for elders and those in need, problems of turning around the car when driving and etc. Eventually the mitigation methods of the negative effects of the LRT on community has been recommended as: the socio-economic impact of the light rail transit on the existing community should be studied in detail before the implementation; the light rail transit should be built underground or on the existing level of the public street to reduce the socio-economic disturbance of the adjacent community; the LRT station distances and facilities should be considered the elders and those in need and the spacing between the distance of the pedestrian cross should be also considered to minimize the negative impact of the LRT on social interaction of the adjacent communities living in the opposite side of the LRT. , .
THE SOCIAL AND ECONOMIC IMPACTS OF PUBLIC TRANSPORTATION ON ADJACENT COMMUNITIES: THE CASE OF EAST-WEST ROUTE OF THE ADDIS ABABA LIGHT RAIL TRANSIT
(EiABC, 2019-06) Tadesse, GEBEYEW; Professor Mintesnot G. Woldeamanuel (PhD)
The Addis Ababa Light Rail Transit system is the first modern mass transit system for Ethiopia as well as for Sub Saharan Africa. Although, the Addis Ababa LRT lines/ stations thought to bring either positive or negative or both social-economic impacts on the adjacent communities, after it has been launched there was/were no research done focusing on the socio-economic impacts the LRT on the adjacent community. Therefore, the purpose of this study was to assess the socio-economic impacts of the light rail transit line/stations on the community.To conduct the research, about six LRT stations along the East-West LRT line from Coca-Cola to Ayat were selected by bypassing 3 LRT stations to embrace the Coca-Cola LRT station which is service dominate area, Megenagna the active commercial area and Ayat the residential dominate area since the study focus on the adjacent residential, commercial and social services. Then, random data collection methods were used to collect the data from the communityaround each LRT stations. Questionnaire surveys, interview and observations methods were used to collect data. There were 720 respondents for the questionnaires and 20 people for an interview to consolidate the quantitative data. Then, the descriptive statistics and spatial analysis methods were administered for data analysis. Using the above approaches, the social and economic impact of the LRT on community in residential, commercial and social service were analyzed.As the result of this, the social and economic impact of the LRT on adjacent community in residential, commercial and social service were analyzed separately using the social and economic impact indicators of the LRT. The community living in the residential areas uses the LRT the most for their trip purpose than the rest of the other adjacent land uses, while followed by the community in the social service, and the least percentage of the adjacent community were those in social services. The LRT has brought both positive and negative socio-economic impacts on the adjacent communities having varied frequency of responses from family to family as well as from station to station. The positive impacts of the LRT for the adjacent community were the transport cost reduction, travel time reduction, increasing volume of retailers around the LRT stations, increasing the volume of the renters in the communities, means of transportations for the community and etc. In contrast to this, the negative impacts of the LRT were segregation of the adjacent communities around the LRT, reduction of the customers from some business activities, long walking distance to access the opposite side of the LRT, inconvenience of the stations for elders and those in need, problems of turning around the car when driving and etc. Eventually the mitigation methods of the negative effects of the LRT on community has been recommended as: the socio-economic impact of the light rail transit on the existing community should be studied in detail before the implementation; the light rail transit should be built underground or on the existing level of the public street to reduce the socio-economic disturbance of the adjacent community; the LRT station distances and facilities should be considered the elders and those in need and the spacing between the distance of the pedestrian cross should be also considered to minimize the negative impact of the LRT on social interaction of the adjacent communities living in the opposite side of the LRT.

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