Abstract
Abstract Gullies and other forms of erosion have been the greatest environmental problem and catastrophe in most high- and low-income countries. The challenge posed by soil erosion has compromised agricultural productivity, environmental biodiversity and food safety for the world's population. It is important to identify vulnerable areas to soil erosion in each region to initiate remedial measures. This study demonstrates the use of watershed morphometry coupled with weighted sum analysis (WSA) to estimate the soil erosion susceptibility of the Imo River Basin sub-watersheds (SWs) in South-Eastern Nigeria using satellite remote-sensing data and geographic information system (GIS) analysis. To this end, Shuttle Radar Topography Mission (SRTM), a Digital Elevation Model (DEM) with 30 m spatial resolution was used to extract and analyse 18 morphometric parameters including basic, linear, shape and relief. The method of receiver operating characteristics (ROC) curves was used to validate the model's prediction accuracy. This morphometry-based analysis resulted in the SWs being classified into zones of low, medium, high and very high erosion susceptibility. With regard to erosion susceptibility, 41.51% of the basin (2494.68 km2) is in the very high priority zone; while 10.50%, 44.33% and 3.66% of the basin are in the high, medium and low priority zones respectively. Validation of the final erosion susceptibility map showed a prediction accuracy of 81%. The use of satellite imagery and morphometric analysis in this study was cost- and time-effective for identifying areas susceptible to soil erosion.
Highlights
Soil is a limited resource that is important for food production, carbon sequestration, water and nutrient management, contaminant filtration, biodiversity improvement, strong heritage, and climate regulation (Arshad, Martin 2002, Panagos et al 2019)
This study demonstrates the use of watershed morphometry coupled with weighted sum analysis (WSA) to estimate the soil erosion susceptibility of the Imo River Basin sub-watersheds (SWs) in South-Eastern Nigeria using satellite remote-sensing data and geographic information system (GIS) analysis
This study successfully classified the Imo River Basin in South-East Nigeria into priority zones based on susceptibility to soil erosion, using a modified geomorphometric prioritisation approach
Summary
Soil is a limited resource that is important for food production, carbon sequestration, water and nutrient management, contaminant filtration, biodiversity improvement, strong heritage, and climate regulation (Arshad, Martin 2002, Panagos et al 2019). The effect of water-driven soil erosion on the global market and food supply reflects an estimated financial loss of USD 8–40 billion, a decrease in food production of 33.7 million tonnes and a 48 billion cubic metres rise in water usage (Sartori et al 2019) In nations such as Brazil, China, India and low-income households worldwide, these impacts are felt more intensely (Nkonya et al 2016, Sartori et al 2019). Cumulative expenditure projections to minimize the on-site impacts of land degradation (e.g. production losses) and its off-site implications (e.g. biodiversity losses and water body siltation) contribute to values of USD 400 billion per annum (Nkonya et al 2016) These numerical values were obtained in soil loss studies utilising Universal Soil Loss Equation (USLE) or related techniques, without any consideration of gully erosion (Alencar et al 2020)
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