Browsing by Author "Mwangi, Patricia"

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    Evaluating the Spatio-Temporal Distribution of Nitrogen Dioxide, Land Surface Temperature and NDVI in Nairobi City County
    (ISPRS-Annals, 2024-11) Mwangi, Patricia
    Cities are becoming larger and it is estimated that by the year 2050, more than 6 billion people will be living in cities. As cities expand and grow, the quality of life and conditions will also transform. An integral part of environmental studies has been statistical analysis in modelling the spatial dynamics of land use changes. The research involved the use of satellite imagery to determine yearly averaged values of LST and NDVI from Landsat 8 OLI/TIR and monthly mean values of Nitrogen Dioxide (NO2) from Sentinel 5-Precursor (Sentinel-5P) across Nairobi City County. The datasets covered the period 2019, 2020, 2021, 2022 and 2023 and were analysed in Google Earth Engine. Results indicated that the yearly mean values in NO2 and LST in 2020 reduced by 2% and 12% respectively from 2019, while the mean NDVI value significantly increased by 28% in 2020 from 2019. NO2 has a negative correlation with LST in all years and a positive correlation with NDVI. Pearson correlation with population densities in constituencies in Nairobi in 2019 and 2023 indicate a negative correlation with NDVI and a positive correlation with NO2 and LST. Constituencies that have higher population densities tend to have lower vegetation densities and higher NO2 concentrations and temperature. Vegetation therefore plays a crucial role in air quality and that climatic factors such as precipitation and temperature influence the concentration of pollutants.
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    Land Use and Land Cover Changes Using Orfeo Tool Box Open-Source Classifier within an Urban River Riparian Reserve of Nairobi River, Kenya
    (Journal of Geography and Regional Planning, 2025-03) Odongo, Malachi Atieno; Mireri, Caled; Mwangi, Patricia
    Urban riparian reserves are a vital source of ecosystem services for urban dwellers. These zones support urban food production, environmental quality, and are home to rich biodiversity of flora and fauna. Even though urban riparian zones offer many benefits to the urban dwellers, the same zones are under tremendous threats from increased anthropogenic activities resulting from Land Use Land Cover (LULC) changes. Nairobi River is a perfect example where urban pressure emanating from the expansion of Nairobi City has undergone immense LULC changes for the past 20 years. Therefore, remotely sensed data could be used to provide detailed information for changes caused by human activities especially within riverine environment using open-source classifiers such as Orfeo Tool Box (OTB). OTB is an essential open-source Remote Sensing tool in assessing the impacts of changes in urban LULC on the environment. High resolution aerial imagery epoched at 2000, 2010 and 2020 was used to detect and assess information about the predominant LULC, their changes over the years and their potential causes. Four LULC classes of bare-land, vegetation, built up and water were identified and analyzed over a 28 km stretch of Nairobi River segmented at the lower, middle and upper based on the topography. The lower section had the most drastic land use changes especially for the built up and vegetation which both increased steadily at 1 and 1.5% annually, respectively eating up both bare land and water which declined at the rate of 1.7 and 0.8% respectively. Likewise, the middle section was equally found to be invaded by double increase of both built up and vegetation at 2 and 3% for the same 20-year period. On the contrary, the upper section of the Nairobi River area was dominated by urban agriculture which covered almost 50% and increased further to 62% over the period registering a growth of approximately 12% translating into 1.2% per annum. This signifies rapid depletion of the riparian reserves which needed an enforcement mechanism and harmonization of various laws and policies for riparian conservation.