Geodesy and Geomatics

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http://etd.aau.edu.et/handle/12345678/188

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Browsing Geodesy and Geomatics by Author "Andenet Ashagrie (PhD)"

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    Assessment of Groundwater Recharge Change Using WetSpass Model in the Birr Watershed, Abay Basin, Ethiopia.
    (Addis Ababa University, 2023-06) Yiheys Degu; Andenet Ashagrie (PhD)
    Understanding the long-term spatial extent of environmental and LULC changes in different time epochs helps to evaluate the impact of climate and LULC changes on water resources. Therefore, estimating the spatial and temporal extent of groundwater recharge in response to climate and LULC changes are crucial for the proper management of the water resources in the watershed. This study quantifies the effects of climate and LULC change on groundwater recharge for the Birr watershed from 1990-2020 periods using WetSpass model. The LULC maps of the study area were classified from multi-temporal Landsat imageries of Landsat 5(TM), Landsat 7(ETM+), and Landsat 8(OLI) using supervised maximum likelihood classification algorithm. The accuracy of classified images was checked by overall accuracy and kappa coefficient. In the study area, agriculture, built-up, and bare land increases through time while grassland, forest, wetland, and shrubland decreases during the last three decades due population growth and rapid expansion of farmland. The monthly reanalysis of climatological satellite products of precipitation, temperature, and windspeed maps was prepared from the decadal average of 1990-1999, 2000-2009, and 2010-2020 for the model simulation. The trend of the climate change in the watershed were analyzed and tested by Mann Kendall test R programming software. The temperature in the watershed has increasing trend over the last 30 year and increase by 0.033oc per year. Whereas, rainfall and wind speed have no significant trend in 95% confidence level. Moreover, a 12m resolution ALOSDEM was used to delineate the watershed and to develop slop and elevation input maps. The slope and elevation maps were finally resampled to 30m resolution. The study result shows that the annual groundwater recharge in the watershed decreases on average from 162.3mm to 128.6mm in from the first phase to the second phase and declines to 121.2mm in the third phase. it is important to take LULC conservation mechanisms and environmental rehabilitation measures in the study area. The study gives a piece of baseline information about impact of climate and LULC on the groundwater recharge of the study area for policymakers and the society of the watershed.
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    Assessment of Urbanization and its Impact on Agricultural Land a case of Motta town, Ethiopia
    (Addis Ababa University, 2024-06) Muhammed Belale; Andenet Ashagrie (PhD)
    Urbanization poses significant challenges to the sustainability of agricultural land, which plays a crucial role in food security and local economies in rapidly urbanizing areas. The study assesses the impact of urbanization on agricultural land in Motta town using Geographic Information System (GIS) and remote sensing techniques. Land use and land cover (LULC) changes from 1992 to 2023 were analysed using Landsat satellite images from the United States Geological Survey (USGS). Both Supervised and unsupervised classification methods of classification were used to classify four land use classes namely built-up area, vegetation, bare land, and agricultural land. The study compared classification algorithms including Support Vector Machine (SVM), Maximum Likelihood Classification (MLC), and unsupervised classification based on their results and accuracy. Additionally, urbanization indices such as New Built-up Index (NBI), Urbanization intensity Index (UII), and Normalized Difference Built-up Index (NDBI) were employed to assess urbanization dynamics. Results indicate a consistent trend of agricultural land loss and built-up area increase. SVM classification shows built-up areas increasing from 323 hectares in 1992 to 607 hectares in 2023, with agricultural land decreasing from 944 hectares to 510 hectares. MLC classification similarly reveals an increase in built-up areas from 534 hectares to 757 hectares and a decrease in agricultural land from 791 hectares to 352 hectares by 2023. Unsupervised classification identifies an increase in built-up areas from 510 hectares to 910 hectares and a decrease in agricultural land from 695 hectares to 346 hectares over the studied period. Accuracy assessments confirm SVM as the most accurate method. The study concludes that urban expansion significantly diminishes agricultural land in Motta town and suggests implementing sustainable land use policies and employing satellite remote sensing for effective monitoring of urban sprawl to mitigate further agricultural land loss
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    Assessment of Vegetation Cover Change in Urban Green Spaces, a Case Study of Addis Ababa, Ethiopia
    (Addis Ababa University, 2024-06) Melkamu Tarekegn; Andenet Ashagrie (PhD)
    Urban green space (UGS) is crucial for maintaining ecological balance in rapidly urbanizing areas. This study aimed to estimate UGS and quantify oxygen production in Addis Ababa, Ethiopia, for the years 2017 and 2024 using Geographic Information System (GIS) and Remote Sensing (RS) technologies. Sentinel-2A satellite imagery was employed to analyze the Normalized Difference Vegetation Index (NDVI) and Normalized Difference Built-up Index (NDBI), assessing changes in vegetation cover and built-up areas. UGS was categorized into dense vegetation, sparse vegetation, and shrub and grassland to estimate oxygen production. The results revealed a significant decline in green spaces and an expansion of built-up areas from 2017 to 2024, indicating rapid urbanization. In 2017, UGS covered 18,818.33 hectares, producing an estimated 33,872.994 tons of oxygen per year. Detailed oxygen production for 2017 included dense vegetation (2,663.39 tons/year), sparse vegetation (2,613.72 tons/year), and shrub and grassland (3,299.22 tons/year). By 2024, UGS reduced to 16,842.17 hectares, with an estimated oxygen production of 30,315.906 tons/year, including dense vegetation (2,862.129 tons/year), sparse vegetation (3,017.96 tons/year), and shrub and grassland (2,402.379 tons/year). Accuracy assessments using Google satellite imagery and ground-collected GPS data validated the classification results. These findings highlight the ecological impact of diminishing green spaces due to urbanization. This research underscores the urgent need for sustainable urban planning and the preservation of green spaces in Addis Ababa to mitigate adverse environmental effects and maintain ecological balance
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    Evaluating The Status of Land Use Land Cover Change: A Case Study of East Gojjam Zone Debre Markos Town, Ethiopia
    (Addis Ababa University, 2024-02) Dawit Belay; Andenet Ashagrie (PhD)
    This research was conducted to evaluate the status of urban land use land cover change. To analyze the LULC change of this study satellite images (Landsat 1986, 2003 and 2020) have been used for retrieving information, adopting image classification method. In addition accuracy analysis has been done by comparing the reference data with the classification results to evaluate the effectiveness of the image classification. The changes between the defined years was evaluated using land use Land cover maps that belongs to different years adopting cross tabulation and overlay analysis methods. The main aim of this study was to evaluate the status of urban land use land cover change in the study area. The result indicates that the main changes in the study area were the transformation of Agricultural Lands 41.62%, 32.60 changes 22.5 % and converted into Built up lands in the study area. Accordingly, around 980 ha of area of Agricultural land were transformed to build up in the last two decades.
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    The Use of GIS and Remote Sensing for Land Use/ Land Cover Change Analysis: The case of Dejen Town, Ethiopia
    (Addis Ababa University, 2024-06) Abebaw Habtamu; Andenet Ashagrie (PhD)
    Technologies like geographic information system (GIS) and Remote Sensing (RS) are used to monitor urbanization, map it, and monitor environmental changes. Since Dejen town is expanding improperly due to growth of population and improper settlers from remote/rural areas to the city, planned development and up-to-date information is needed on the Land Use and Land Cover (LULC) and population of the town to improve the problems. The project's overall goal was to use GIS and remote sensing methods to study LULC classification and analyze trends in Dejen town between 1993 and 2023. The literature review mainly focused on the concepts and definitions of GIS, Remote Sensing, LULC, LULC Mapping, LULC Change detections, and causes for urban expansion in the study area. The Landsat imagery data were used for the research study. Those data were processed using ArcGIS 10.7, and ERDAS (Earth Resource Data Analysis System) software. Accordingly, the satellite images were used to monitor LULC changes from the years 1993-2023 for the five identified LULC classes. The Landsat images were classed into built-up and non-built-up areas to concentrate on urbanization after five distinct kinds of land use and land cover classes were found using supervised classification. The finding of the study showed that, the built up area has increased from 177ha in 1993 to 958ha in 2023, forest area increased from 0.45ha to 107ha, barren land decreased from 334ha to 162ha, agricultural land decreased from 1613ha to 868ha and a slight change occurred in open area decreased from 269ha to 298ha. Built up area has exhibited the most noticeable changes (7.39% to 40.03%) from 1993 to 2023, which come from agricultural land and barren land. The result of the study showed that the most fertile and productive part of the agricultural land has changed to urban land. The study results provide valuable information for the city administration for planning unmanaged urban growth. It also provides useful knowledge for policy relevant land administration for future development related to land use plan associated to urban expansion.