Urbanization And Landscape Dynamics In Ethiopia Based On Remotely Sensed Data And Geospatial Analysis

Over the years,urban spatial growth has stimulated an enormous amount of change in land use configurations worldwide.These changes have precipitated urban sprawl and massive uncontrolled growth,which pose a severe risk to sustainable development.However,there is a lack of detailed comparative exploration of urban development among different cities over a relatively long period in many developing nations,particularly in Africa,and research is mostly limited to single and large cities.Also,the fundamental ideas concerning urbanization are primarily based on studies performed in large cities.Therefore,the main objective of this dissertation is to investigate and compare urbanization trends,the dynamics of urban landscape patterns,and the effects on the natural environment through multi-temporal satellite remote sensing analyses at varied sizes of Ethiopian cities.Specifically,this study provides a comprehensive comparative analysis of the growth and spatial patterns of urban development in the three major cities of Ethiopia(Addis Ababa,Adama,and Hawassa).Besides,the applicability of diffusion and coalescence theory on the evolution of these cities has been tested.In addition,impacts of urban expansion in small cities and its implications on landscape structures in six towns of the Oromia Special Zone surrounding Finfinnee has been investigated.Furthermore,the effects of the spatial patterns of urban green space(UGS)on land surface temperature(LST)has analyzed.Methodologically,integrated frameworks,landscape metrics,urban growth type,gradient model,and built-up density analysis were applied to characterize and compare the dynamics of landscape structures,urban expansion patterns,process,and overall growth status in the cities.Whereas,spatial metrics combined with different statistical approaches at varied scales were used to investigate the relationships between UGS and LST.Spatially explicit Landsat imagery from 1987 to 2019 was used to generate the land cover and LST maps.The result revealed that all the studied cities experienced accelerated growth in the urbanized areas,but the cities with a larger initial urbanized size were associated with lower expansion rates.Differences in extent and direction of expansion in each major city were mostly related to physical features,urban master plans,and policies,with an increase in the irregularity and dispersion of urban growth,representing strong evidence of urban sprawl.The ecological analysis confirmed a highly fragmented urban landscape,a significant loss of natural land covers,and disconnected and complicated agro-vegetation patches in all towns,suggesting a lack of rigorous implementation of the master plan.The spatiotemporal analysis confirmed that the urbanization processes of Addis Ababa and Adama were consistent,and Hawassa city diverged from expectations based on diffusion and coalescence theory.Furthermore,results from the study indicated that the UGS patches with aggregated,regular and simple shape,and connected across the urban landscape is more active to decrease the LST than that of fragmented and complicated shape patterns.This suggesting that in addition to increasing the amount of UGS,optimizing the spatial structure of UGS,can be an effective and useful action to mitigate the UHI impacts.Changing the spatial size had a significant effect on the relationship between LST and UGS patterns.It also suggested that the configuration metrics are more sensitive to spatial scale than composition metrics.The relationships between configuration metrics and LST could be radically changed when applying different statistical methods.The importance of controlling the effects of the proportion of green spaces when calculating the impacts of the spatial configuration of UGS on LST is further underlined.In general,large cities with strong economic growth in a country fail to effectively control the scattered nature of urban growth.In addition,the small cities would have a limited physical and demographic footprint and relatively less contribution to the national economic agglomeration;nonetheless,they can have a notable and important impact in terms of their ecological and environmental influence.Thus,the study suggests policies for monitoring such dynamics and protecting agro-environmental connectivity in the cities.The proposed methods in this study can help identify the priority areas to be selected for conservation,ecological and environmental improvements,urban densifications,and agro-forest system restoration.