Analysis of Pressure Drivers within an Urban River Riparian Reserve: A Case of Nairobi River in Kenya

Rapid urban development is characterized by encroachments, haphazard urban growth, and unplanned land-use change. Nairobi river is a perfect example where urban pressure emanating from the expansion of Nairobi City has undergone immense land use land cover changes for the past 20 years. Pressure drivers as a result of anthropogenic activities such as expansion of human settlements, urban agriculture and commercial activities continue to compete for the fragile ecosystem spaces of the riparian reserves which ideally should have been left for biodiversity, pollution filtration, flow moderation and slope stabilization. The aim was therefore to analyze these pressure drivers in three sampled river riparian segments. The methodology adopted involved a sampled survey of 650 respondents drawn from the segmented sections of Nairobi River of Upper, Middle and Lower segments where a mobile data questionnaireusing Open Data Kit (ODK) with geolocation capability was administered to the various users of the riparian areas. The segmentation was done based on the topography and elevations as per the available Digital Terrain Model (DTM). The results showed that urban agricultural activities consisting of vegetables, maize and banana farms dominated upper segment at 69% while commercial ventures including shops, open markets, car wash and garages constituted 79% of the middle segment and residential usage comprising of re-used old iron sheets houses, makeshift shelters and some semi-permanent structures at 89% in the lower segment signifying significant degradation from crop cultivation of the river slopes, pollution infiltration and loss of biodiversity respectively. Continued encroachment by these pressure drivers have subsequently caused depletion of the riparian space to perform its functions which if left unmitigated could result to more floods as recently depicted in Nairobi City with more property and lives being lost.