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.

 

Key words: Remote sensing, land use land cover, random forest, urban rivers, digital terrain model, geographical information system.