Environmental and socio-economic impacts assessment of stone quarrying along River Mutonga, Meru County, Kenya

Abstract

Stone quarrying is a key source of construction materials and livelihood opportunities in developing countries, yet it poses major environmental and socio-economic challenges. This study examined the spatial distribution, spatiotemporal dynamics, ecological and socio-economic impacts of stone quarrying along River Mutonga in Imenti South, Meru County, Kenya. Geospatial techniques were employed to map active and abandoned quarry sites using GPS coordinates and high-resolution satellite imagery. Sentinel-2 imageries for the years 2015, 2020, and 2025 were processed using the Random Forest (RF) classifier in Google Earth Engine (GEE) to detect land use and land cover (LULC) changes. Household surveys were conducted to assess the perceived ecological and socio-economic impacts of stone quarrying in the study area. The results revealed that quarrying activities were concentrated along the river, where accessibility and exposed granite deposits have promoted intensive extraction. A total of 20 quarry sites were mapped, comprising 11 active and 9 abandoned quarries, ranging from about 0.15 ha to 1.20 ha in size. Land Use/Land Cover (LULC) analysis showed a marked transformation of the river landscape between 2015 and 2025. Quarry areas increased by 0.18 km² (61.8%), with built-up areas and bare land also expanding in area coverage by + 0.17 km² (100%) and + 2.23 km² (56.03) respectively, reflecting increasing demand for construction materials and growing anthropogenic pressure in the study region. Quarrying in the study area was perceived to have both positive and negative impacts. While it contributed significantly to household income and community development, residents reported considerable environmental degradation, including land degradation, vegetation loss, and water pollution. Safety concerns were also reported, particularly in relation to accidents at quarry sites and hazards from water-filled abandoned quarries. The study highlights the urgent need for sustainable quarry management strategies, including post-extraction rehabilitation, environmental monitoring, and enforcement of land use regulations.