Environmental Challenges 5 (2021) 100260 Contents lists available at ScienceDirect Environmental Challenges journal homepage: www.elsevier.com/locate/envc Erosion risk assessment through prioritization of sub-watersheds in Nyabarongo river catchment, Rwanda Luc Cimusa Kulimushi a,∗ , Pandurang Choudhari b , Abias Maniragaba a , Ahmed Elbeltagi c , Maurice Mugabowindekwe d , Gaspard Rwanyiziri d,e , Rutazuyaza Vaillant Byizigiro f , Santosh Murlidhar Pingale g , Sudhir Kumar Singh h a Faculty of Environmental studies, University of Lay Adventists of Kigali, P.O. Box: 6392, Kigali, Rwanda b Department of Geography, University of Mumbai, Mumbai, India c Agricultural Engineering Deptartment, Faculty of Agriculture, Mansoura University, Mansoura 35516, Egypt d Centre for Geographic Information Systems and Remote Sensing (CGIS), College of Science and Technology, University of Rwanda, Nyarugenge Campus. P.O. Box: 3900, Kigali, Rwanda e Department of Geography and Urban Planning, College of Science and Technology, University of Rwanda, Nyarugenge Campus. P.O. Box: 3900, Kigali, Rwanda f Geography, College of Education, University of Rwanda, Rukara Campus. P.O. Box: 55, Kayonza, Rwanda g Hydrological Investigations Division, National Institute of Hydrology (NIH) Roorkee, 247667, India h K. Banerjee Centre of Atmospheric & Ocean Studies, IIDS, Nehru Science Centre, University of Allahabad, Prayagraj, Uttar Pradesh 211002, India a r t i c l e i n f o Keywords: Analytical hierarchy process Watershed prioritization Erosion hazard rate index Hierarchical cluster analysis Principal component analysis Nyabarongo catchment Rwanda a b s t r a c t Soil erosion is a multi-dimension problem that attracted the attention of researchers and planners worldwide. Literature reports, soil conservation strategies should be integrated with the priority assessment to deal with such a problem and taking up a focus according to the priority order. However, in spite of various forms of land and water degradation in Rwanda, a holistic investigation or multi-criteria based watersheds prioritization that integrate various aspects and methods has yet to be assessed. Thus, Nyabarongo River Catchment which is the major river catchment in Rwanda that drains about 33% of the total Rwanda coverage has been selected and sub- watersheds were grouped into three order clusters (C1, C2, and C3) using Hierarchical Cluster Analysis (HCA). The priority assessment was estimated using the combination of Compound parameter index (Ci) and Erosion Hazard Rate Index (EHRI) derived from the Analytical Hierarchy Process (AHP) in Geographic Information System (GIS) using remote sensing, soil and geology data. Based on the literature, the Ci technique, in general, considered four parameters viz. morphometric analysis dimensionally reduced using the Principal Component Analysis (PCA) together with land cover, soil, and geology. Whereas EHRI considered five Erosion Hazard Parameters (EHPs) viz. Soil Loss (SL), Sediment Production Rate (SPR), Sediment Transport Index (STI), Runoff Potential (RP), and Slope. The priority assessment was categorized into High, Moderate, and Low priority classes. The priority assessment based on Ci and EHRI provided the same outcome. They noticed high priority in sub-watersheds under cluster C2 account for (35.94%), those under cluster C3 comprise for (16.27%) were identified as a moderate priority, and sub-watersheds belonging to cluster C1 account for (47.8%) falling under low priority sub-watersheds for conservation measures. Therefore, effective soil conservation measures at a priority basis are needed for sustained productivity while minimizing undesirable effects on the environment. 1. Introduction Soil erosion is one of the greatest environmental concerns world- wide. Beyond onsite degradation of land through the transport of topsoil affecting soil productivity, erosion alters water quality through sedimen- tation of the eroded material into the water system and thereby mak- ing water unsuited for consumption and services (Diwakar and Thakur, 2012). This natural phenomenon is most pressing in high-land regions (Kulimushi et al., 2021a) such as the biophysical condition of Rwanda. ∗ Corresponding author. E-mail addresses: kcimusa@gmail.com, kcimusa@unilak.ac.rw (L.C. Kulimushi). Like other regions of Rwanda, the Nyabarongo catchment is ex- tremely susceptible to soil erosion and associated risks (Karamage et al., 2016). This vulnerability is attributed to the dynamism of erosive agents, those are hilly mountains and steep slopes, heavy rainfall, fragile soil, and high pressure of human activities to the natural environment through the rapid change in land use/land cover (LULC) (Kulimushi et al. 2021b). As demonstrated (Akinyemi, 2017), Rwanda is one of Africa’s most ecologically sensitive environments under severe pressure from human activities, this accelerating soil degradation in the form of https://doi.org/10.1016/j.envc.2021.100260 Received 8 June 2021; Received in revised form 28 July 2021; Accepted 31 August 2021 2667-0100/© 2021 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)